Add universal compaction to db_stress nightly build

Summary: Most code change in this diff is code cleanup/rewrite. The logic changes include: (1) add universal compaction to db_crashtest2.py (2) randomly set --test_batches_snapshots to be 0 or 1 in db_crashtest2.py. Old codes always use 1. (3) use different tmp directory as db directory in different runs. I saw some intermittent errors in my local tests. Use of different tmp directory seems to be able to solve the issue. Test Plan: Have run "make crashtest" for multiple times. Also run "make all check" Reviewers: emayanke, dhruba, haobo Reviewed By: emayanke Differential Revision: https://reviews.facebook.net/D12369
Made merge_oprator a shared_ptr; and added TTL unit tests
2026-11-07 03:22:34 -05:00 · 2013-08-20 17:37:49 -07:00 · 2013-08-20 13:35:28 -07:00 · 2013-08-19 14:29:40 -07:00 · 2013-08-19 14:27:19 -07:00 · 2013-08-19 13:37:04 -07:00
164 changed files with 16906 additions and 3037 deletions
@@ -1,13 +1,16 @@
 build_config.mk
 *.a
-*.o
+*.arc
+*.d
 *.dylib*
+*.gcda
+*.gcno
+*.o
 *.so
 *.so.*
 *_test
-*.arc
-*.d
 db_bench
+db_repl_stress
 db_stress
 ldb
 leveldb_server
@@ -15,4 +18,6 @@ leveldb_shell
 manifest_dump
 sst_dump
 util/build_version.cc
-db_repl_stress
+build_tools/VALGRIND_LOGS/
+coverage/COVERAGE_REPORT
+util/build_version.cc.tmp
@@ -14,13 +14,13 @@ OPT += -O2 -fno-omit-frame-pointer -momit-leaf-frame-pointer
 #-----------------------------------------------

 # detect what platform we're building on
-$(shell ./build_detect_platform build_config.mk)
+$(shell (cd build_tools/; ROCKSDB_ROOT=.. ./build_detect_platform ../build_config.mk))
 # this file is generated by the previous line to set build flags and sources
 include build_config.mk

-WARNING_FLAGS = -Wall -Werror -Wno-unused-parameter -Wno-sign-compare
+WARNING_FLAGS = -Wall -Werror
 CFLAGS += -g $(WARNING_FLAGS) -I. -I./include $(PLATFORM_CCFLAGS) $(OPT)
-CXXFLAGS += -g $(WARNING_FLAGS) -I. -I./include $(PLATFORM_CXXFLAGS) $(OPT) -std=gnu++0x
+CXXFLAGS += -g $(WARNING_FLAGS) -I. -I./include $(PLATFORM_CXXFLAGS) $(OPT) -std=gnu++0x -Woverloaded-virtual

 LDFLAGS += $(PLATFORM_LDFLAGS)

@@ -31,48 +31,54 @@ MEMENVOBJECTS = $(MEMENV_SOURCES:.cc=.o)
 TESTUTIL = ./util/testutil.o
 TESTHARNESS = ./util/testharness.o $(TESTUTIL)
 VALGRIND_ERROR = 2
-VALGRIND_DIR = VALGRIND_LOGS
+VALGRIND_DIR = build_tools/VALGRIND_LOGS
 VALGRIND_VER := $(join $(VALGRIND_VER),valgrind)
 VALGRIND_OPTS = --error-exitcode=$(VALGRIND_ERROR) --leak-check=full

 TESTS = \
 	arena_test \
+	auto_roll_logger_test \
+	block_test \
 	bloom_test \
 	c_test \
 	cache_test \
 	coding_test \
-	histogram_test \
 	corruption_test \
 	crc32c_test \
 	db_test \
 	dbformat_test \
 	env_test \
+	filelock_test \
 	filename_test \
 	filter_block_test \
+	histogram_test \
 	log_test \
+	manual_compaction_test \
 	memenv_test \
+	merge_test \
+	redis_test \
+	reduce_levels_test \
 	skiplist_test \
+	stringappend_test \
 	table_test \
-	block_test \
+	ttl_test \
 	version_edit_test \
 	version_set_test \
-	reduce_levels_test \
-	write_batch_test \
-	auto_roll_logger_test \
-	filelock_test
-
+	write_batch_test

 TOOLS = \
-	manifest_dump \
        sst_dump \
        db_stress \
        ldb \
 	db_repl_stress

-PROGRAMS = db_bench $(TESTS) $(TOOLS)
+PROGRAMS = db_bench signal_test $(TESTS) $(TOOLS)
 BENCHMARKS = db_bench_sqlite3 db_bench_tree_db

-LIBRARY = libleveldb.a
+# The library name is configurable since we are maintaining libraries of both
+# debug/release mode.
+LIBNAME = librocksdb
+LIBRARY = ${LIBNAME}.a
 MEMENVLIBRARY = libmemenv.a

 default: all
@@ -81,15 +87,15 @@ default: all
 ifneq ($(PLATFORM_SHARED_EXT),)

 ifneq ($(PLATFORM_SHARED_VERSIONED),true)
-SHARED1 = libleveldb.$(PLATFORM_SHARED_EXT)
+SHARED1 = ${LIBNAME}.$(PLATFORM_SHARED_EXT)
 SHARED2 = $(SHARED1)
 SHARED3 = $(SHARED1)
 SHARED = $(SHARED1)
 else
 # Update db.h if you change these.
-SHARED_MAJOR = 1
-SHARED_MINOR = 5
-SHARED1 = libleveldb.$(PLATFORM_SHARED_EXT)
+SHARED_MAJOR = 2
+SHARED_MINOR = 0
+SHARED1 = ${LIBNAME}.$(PLATFORM_SHARED_EXT)
 SHARED2 = $(SHARED1).$(SHARED_MAJOR)
 SHARED3 = $(SHARED1).$(SHARED_MAJOR).$(SHARED_MINOR)
 SHARED = $(SHARED1) $(SHARED2) $(SHARED3)
@@ -100,15 +106,25 @@ $(SHARED2): $(SHARED3)
 endif

 $(SHARED3):
-	$(CXX) $(LDFLAGS) $(PLATFORM_SHARED_LDFLAGS)$(SHARED2) $(CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) $(SOURCES) -o $(SHARED3)
+	$(CXX) $(LDFLAGS) $(PLATFORM_SHARED_LDFLAGS)$(SHARED2) $(CXXFLAGS) $(COVERAGEFLAGS) $(PLATFORM_SHARED_CFLAGS) $(SOURCES) -o $(SHARED3)

 endif  # PLATFORM_SHARED_EXT

 all: $(SHARED) $(LIBRARY) $(PROGRAMS)

+.PHONY: blackbox_crash_test check clean coverage crash_test ldb_tests \
+	release tags valgrind_check whitebox_crash_test
+
 release:
-	make clean
-	OPT=-DNDEBUG make -j32
+	$(MAKE) clean
+	OPT=-DNDEBUG $(MAKE) -j32
+
+coverage:
+	$(MAKE) clean
+	COVERAGEFLAGS="-fprofile-arcs -ftest-coverage" $(MAKE) all check
+	(cd coverage; ./coverage_test.sh)
+	# Delete intermediate files
+	find . -type f -regex ".*\.\(\(gcda\)\|\(gcno\)\)" | xargs --no-run-if-empty rm

 check: all $(PROGRAMS) $(TESTS) $(TOOLS) ldb_tests
 	for t in $(TESTS); do echo "***** Running $$t"; ./$$t || exit 1; done
@@ -116,7 +132,16 @@ check: all $(PROGRAMS) $(TESTS) $(TOOLS) ldb_tests
 ldb_tests: all $(PROGRAMS) $(TOOLS)
 	python tools/ldb_test.py

+crash_test: blackbox_crash_test whitebox_crash_test
+
+blackbox_crash_test: db_stress
+	python -u tools/db_crashtest.py
+
+whitebox_crash_test: db_stress
+	python -u tools/db_crashtest2.py
+
 valgrind_check: all $(PROGRAMS) $(TESTS)
+	mkdir -p $(VALGRIND_DIR)
 	echo TESTS THAT HAVE VALGRIND ERRORS > $(VALGRIND_DIR)/valgrind_failed_tests; \
 	echo TIMES in seconds TAKEN BY TESTS ON VALGRIND > $(VALGRIND_DIR)/valgrind_tests_times; \
 	for t in $(filter-out skiplist_test,$(TESTS)); do \
@@ -130,119 +155,148 @@ valgrind_check: all $(PROGRAMS) $(TESTS)
 	done

 clean:
-	-rm -f $(PROGRAMS) $(BENCHMARKS) $(LIBRARY) $(SHARED) $(MEMENVLIBRARY) $(THRIFTSERVER) */*.o */*/*.o ios-x86/*/*.o ios-arm/*/*.o build_config.mk
+	-rm -f $(PROGRAMS) $(BENCHMARKS) $(LIBRARY) $(SHARED) $(MEMENVLIBRARY) $(THRIFTSERVER) build_config.mk
 	-rm -rf ios-x86/* ios-arm/*
+	-find . -name "*.[od]" | xargs --no-run-if-empty rm
+	-find . -type f -regex ".*\.\(\(gcda\)\|\(gcno\)\)" | xargs --no-run-if-empty rm
+tags:
+	ctags * -R
+	cscope -b `find . -name '*.cc'` `find . -name '*.h'`

+# ---------------------------------------------------------------------------
+# 	Unit tests and tools
+# ---------------------------------------------------------------------------
 $(LIBRARY): $(LIBOBJECTS)
 	rm -f $@
 	$(AR) -rs $@ $(LIBOBJECTS)

-
 db_bench: db/db_bench.o $(LIBOBJECTS) $(TESTUTIL)
-	$(CXX) db/db_bench.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS)
+	$(CXX) db/db_bench.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS) $(COVERAGEFLAGS)

 db_stress: tools/db_stress.o $(LIBOBJECTS) $(TESTUTIL)
-	$(CXX) tools/db_stress.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS)
+	$(CXX) tools/db_stress.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS) $(COVERAGEFLAGS)

 db_repl_stress: tools/db_repl_stress.o $(LIBOBJECTS) $(TESTUTIL)
-	$(CXX) tools/db_repl_stress.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS)
+	$(CXX) tools/db_repl_stress.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS) $(COVERAGEFLAGS)

 db_bench_sqlite3: doc/bench/db_bench_sqlite3.o $(LIBOBJECTS) $(TESTUTIL)
-	$(CXX) doc/bench/db_bench_sqlite3.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) -lsqlite3
+	$(CXX) doc/bench/db_bench_sqlite3.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) -lsqlite3 $(COVERAGEFLAGS)

 db_bench_tree_db: doc/bench/db_bench_tree_db.o $(LIBOBJECTS) $(TESTUTIL)
-	$(CXX) doc/bench/db_bench_tree_db.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) -lkyotocabinet
+	$(CXX) doc/bench/db_bench_tree_db.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) -lkyotocabinet $(COVERAGEFLAGS)
+
+signal_test: util/signal_test.o $(LIBOBJECTS)
+	$(CXX) util/signal_test.o $(LIBOBJECTS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 arena_test: util/arena_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) util/arena_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) util/arena_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 bloom_test: util/bloom_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) util/bloom_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) util/bloom_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 c_test: db/c_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/c_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) db/c_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 cache_test: util/cache_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) util/cache_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) util/cache_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 coding_test: util/coding_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) util/coding_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) util/coding_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)
+
+stringappend_test: utilities/merge_operators/string_append/stringappend_test.o $(LIBOBJECTS) $(TESTHARNESS)
+	$(CXX) utilities/merge_operators/string_append/stringappend_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)
+
+redis_test: utilities/redis/redis_lists_test.o $(LIBOBJECTS) $(TESTHARNESS)
+	$(CXX) utilities/redis/redis_lists_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 histogram_test: util/histogram_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) util/histogram_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o$@ $(LDFLAGS)
+	$(CXX) util/histogram_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o$@ $(LDFLAGS) $(COVERAGEFLAGS)

 corruption_test: db/corruption_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/corruption_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) db/corruption_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 crc32c_test: util/crc32c_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) util/crc32c_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) util/crc32c_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 db_test: db/db_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/db_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) db/db_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)
+
+perf_context_test: db/perf_context_test.o $(LIBOBJECTS) $(TESTHARNESS)
+	$(CXX) db/perf_context_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+
+ttl_test: utilities/ttl/ttl_test.o $(LIBOBJECTS) $(TESTHARNESS)
+	$(CXX) utilities/ttl/ttl_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS) $(COVERAGEFLAGS)

 dbformat_test: db/dbformat_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/dbformat_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) db/dbformat_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 env_test: util/env_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) util/env_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) util/env_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 filename_test: db/filename_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/filename_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) db/filename_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 filter_block_test: table/filter_block_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) table/filter_block_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) table/filter_block_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 log_test: db/log_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/log_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) db/log_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 table_test: table/table_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) table/table_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) table/table_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 block_test: table/block_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) table/block_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) table/block_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 skiplist_test: db/skiplist_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/skiplist_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) db/skiplist_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 version_edit_test: db/version_edit_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/version_edit_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) db/version_edit_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 version_set_test: db/version_set_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/version_set_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) db/version_set_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 reduce_levels_test: tools/reduce_levels_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) tools/reduce_levels_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) tools/reduce_levels_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 write_batch_test: db/write_batch_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/write_batch_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) db/write_batch_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)
+
+merge_test: db/merge_test.o $(LIBOBJECTS) $(TESTHARNESS)
+	$(CXX) db/merge_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 $(MEMENVLIBRARY) : $(MEMENVOBJECTS)
 	rm -f $@
 	$(AR) -rs $@ $(MEMENVOBJECTS)

 memenv_test : helpers/memenv/memenv_test.o $(MEMENVLIBRARY) $(LIBRARY) $(TESTHARNESS)
-	$(CXX) helpers/memenv/memenv_test.o $(MEMENVLIBRARY) $(LIBRARY) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) helpers/memenv/memenv_test.o $(MEMENVLIBRARY) $(LIBRARY) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

-leveldb_shell: tools/shell/ShellContext.o tools/shell/ShellState.o tools/shell/LeveldbShell.o tools/shell/DBClientProxy.o tools/shell/ShellContext.h tools/shell/ShellState.h tools/shell/DBClientProxy.h $(LIBOBJECTS)
-	$(CXX) tools/shell/ShellContext.o tools/shell/ShellState.o tools/shell/LeveldbShell.o tools/shell/DBClientProxy.o $(LIBOBJECTS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+manual_compaction_test: util/manual_compaction_test.o $(LIBOBJECTS) $(TESTHARNESS)
+	$(CXX) util/manual_compaction_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

-DBClientProxy_test: tools/shell/test/DBClientProxyTest.o tools/shell/DBClientProxy.o $(LIBRARY) 
-	$(CXX) tools/shell/test/DBClientProxyTest.o tools/shell/DBClientProxy.o $(LIBRARY) $(EXEC_LDFLAGS) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS)
+rocksdb_shell: tools/shell/ShellContext.o tools/shell/ShellState.o tools/shell/LeveldbShell.o tools/shell/DBClientProxy.o tools/shell/ShellContext.h tools/shell/ShellState.h tools/shell/DBClientProxy.h $(LIBOBJECTS)
+	$(CXX) tools/shell/ShellContext.o tools/shell/ShellState.o tools/shell/LeveldbShell.o tools/shell/DBClientProxy.o $(LIBOBJECTS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

-manifest_dump: tools/manifest_dump.o $(LIBOBJECTS)
-	$(CXX) tools/manifest_dump.o $(LIBOBJECTS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+DBClientProxy_test: tools/shell/test/DBClientProxyTest.o tools/shell/DBClientProxy.o $(LIBRARY)
+	$(CXX) tools/shell/test/DBClientProxyTest.o tools/shell/DBClientProxy.o $(LIBRARY) $(EXEC_LDFLAGS) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS) $(COVERAGEFLAGS)

 filelock_test: util/filelock_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) util/filelock_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) util/filelock_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 auto_roll_logger_test: util/auto_roll_logger_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) util/auto_roll_logger_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) util/auto_roll_logger_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 sst_dump: tools/sst_dump.o $(LIBOBJECTS)
-	$(CXX) tools/sst_dump.o $(LIBOBJECTS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) tools/sst_dump.o $(LIBOBJECTS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)

 ldb: tools/ldb.o $(LIBOBJECTS)
-	$(CXX) tools/ldb.o $(LIBOBJECTS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS)
+	$(CXX) tools/ldb.o $(LIBOBJECTS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)
+
+# ---------------------------------------------------------------------------
+#  	Platform-specific compilation
+# ---------------------------------------------------------------------------

 ifeq ($(PLATFORM), IOS)
 # For iOS, create universal object files to be used on both the simulator and
@@ -254,9 +308,9 @@ IOSVERSION=$(shell defaults read $(PLATFORMSROOT)/iPhoneOS.platform/versionCFBun

 .cc.o:
 	mkdir -p ios-x86/$(dir $@)
-	$(SIMULATORROOT)/usr/bin/$(CXX) $(CXXFLAGS) -isysroot $(SIMULATORROOT)/SDKs/iPhoneSimulator$(IOSVERSION).sdk -arch i686 -c $< -o ios-x86/$@
+	$(SIMULATORROOT)/usr/bin/$(CXX) $(CXXFLAGS) -isysroot $(SIMULATORROOT)/SDKs/iPhoneSimulator$(IOSVERSION).sdk -arch i686 -c $< -o ios-x86/$@ $(COVERAGEFLAGS)
 	mkdir -p ios-arm/$(dir $@)
-	$(DEVICEROOT)/usr/bin/$(CXX) $(CXXFLAGS) -isysroot $(DEVICEROOT)/SDKs/iPhoneOS$(IOSVERSION).sdk -arch armv6 -arch armv7 -c $< -o ios-arm/$@
+	$(DEVICEROOT)/usr/bin/$(CXX) $(CXXFLAGS) -isysroot $(DEVICEROOT)/SDKs/iPhoneOS$(IOSVERSION).sdk -arch armv6 -arch armv7 -c $< -o ios-arm/$@ $(COVERAGEFLAGS)
 	lipo ios-x86/$@ ios-arm/$@ -create -output $@

 .c.o:
@@ -268,17 +322,26 @@ IOSVERSION=$(shell defaults read $(PLATFORMSROOT)/iPhoneOS.platform/versionCFBun

 else
 .cc.o:
-	$(CXX) $(CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) -c $< -o $@
+	$(CXX) $(CXXFLAGS) -c $< -o $@ $(COVERAGEFLAGS)

 .c.o:
-	$(CC) $(CFLAGS) $(PLATFORM_SHARED_CFLAGS) -c $< -o $@
+	$(CC) $(CFLAGS) -c $< -o $@
 endif

+# ---------------------------------------------------------------------------
+#  	Source files dependencies detection
+# ---------------------------------------------------------------------------
+
+# Add proper dependency support so changing a .h file forces a .cc file to
+# rebuild.
+
+# The .d file indicates .cc file's dependencies on .h files. We generate such
+# dependency by g++'s -MM option, whose output is a make dependency rule.
+# The sed command makes sure the "target" file in the generated .d file has
+# the correct path prefix.
 %.d: %.cc
-	$(CXX) $(CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) -MM $< -o $*.d
-	@cp -f $*.d $*.d.tmp
-	@sed -e 's|.*:|$*.o:|' < $*.d.tmp > $*.d
-	@rm -f $*.d.tmp
+	$(CXX) $(CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) -MM $< -o $@
+	@sed -i -e 's|.*:|$*.o:|' $@

 DEPFILES = $(filter-out util/build_version.d,$(SOURCES:.cc=.d))

@@ -287,4 +350,3 @@ depend: $(DEPFILES)
 ifneq ($(MAKECMDGOALS),clean)
 -include $(DEPFILES)
 endif
-
@@ -1,5 +1,7 @@
 rocksdb: A persistent key-value store for flash storage
-Authors: The Facebook Database Engineering Team
+Authors: * The Facebook Database Engineering Team
+         * Build on earlier work on leveldb by Sanjay Ghemawat 
+           (sanjay@google.com) and Jeff Dean (jeff@google.com)

 This code is a library that forms the core building block for a fast
 key value server, especially suited for storing data on flash drives.
@@ -56,6 +58,25 @@ include/env.h
    Abstraction of the OS environment.  A posix implementation of
    this interface is in util/env_posix.cc

-include/table.h
 include/table_builder.h
    Lower-level modules that most clients probably won't use directly
+
+include/cache.h
+    An API for the block cache.
+
+include/compaction_filter.h
+    An API for a application filter invoked on every compaction.
+
+include/filter_policy.h
+    An API for configuring a bloom filter.
+
+include/memtablerep.h
+    An API for implementing a memtable.
+
+include/statistics.h
+    An API to retrieve various database statistics.
+
+include/transaction_log_iterator.h
+    An API to retrieve transaction logs from a database.
+
+
@@ -1,3 +1,3 @@
 * Detailed instructions on how to compile using fbcode and jemalloc

-* Latest release is 1.5.7.fb
+* Latest release is 2.1.fb
@@ -1,4 +0,0 @@
-This directory stores the tests that failed valgrind and the times associated
-with the failed runs.
-"make valgrind_check" can be invoked to call valgrind on the rocksdb tests and
-generate files in this directory
@@ -1,30 +0,0 @@
-#!/bin/sh
-#
-# Record the version of the source that we are compiling.
-# We keep a record of the git revision in util/version.cc. This source file
-# is then built as a regular source file as part of the compilation process.
-# One can run "strings executable_filename | grep _build_" to find the version of
-# the source that we used to build the executable file.
-#
-
-# create git version file
-VFILE=$(mktemp)
-trap "rm $VFILE" EXIT
-
-# check to see if git is in the path
-which git > /dev/null
-
-if [ "$?" = 0 ]; then
-  env -i git rev-parse HEAD | awk ' BEGIN {print "#include \"build_version.h\""} {print "const char * leveldb_build_git_sha = \"leveldb_build_git_sha:" $0"\";"} END {}' >  ${VFILE}
-else
-  echo "git not found"| awk ' BEGIN {print "#include \"build_version.h\""} {print "const char * leveldb_build_git_sha = \"leveldb_build_git_sha:git not found\";"} END {}' > ${VFILE}
-fi
-
-date | awk 'BEGIN {} {print "const char * leveldb_build_git_datetime = \"leveldb_build_git_datetime:"$0"\";"} END {} ' >> ${VFILE}
-echo "const char * leveldb_build_compile_date = __DATE__;" >> ${VFILE}
-echo "const char * leveldb_build_compile_time = __TIME__;" >> ${VFILE}
-
-OUTFILE=util/build_version.cc
-if [ ! -e $OUTFILE ] || ! cmp -s $VFILE $OUTFILE; then
-    cp $VFILE $OUTFILE
-fi
@@ -31,9 +31,9 @@ fi
 # Default to fbcode gcc on internal fb machines
 if [ -d /mnt/gvfs/third-party -a -z "$CXX" ]; then
    if [ -z "$USE_CLANG" ]; then
-        source fbcode.gcc471.sh
+        source ./fbcode.gcc471.sh
    else
-        source fbcode.clang31.sh
+        source ./fbcode.clang31.sh
    fi
 fi

@@ -64,6 +64,9 @@ PLATFORM_SHARED_LDFLAGS="${EXEC_LDFLAGS_SHARED} -shared -Wl,-soname -Wl,"
 PLATFORM_SHARED_CFLAGS="-fPIC"
 PLATFORM_SHARED_VERSIONED=true

+# generic port files (working on all platform by #ifdef) go directly in /port
+GENERIC_PORT_FILES=`cd $ROCKSDB_ROOT; find port -name '*.cc' | tr "\n" " "`
+
 # On GCC, we pick libc's memcmp over GCC's memcmp via -fno-builtin-memcmp
 case "$TARGET_OS" in
    Darwin)
@@ -71,52 +74,52 @@ case "$TARGET_OS" in
        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -DOS_MACOSX"
        PLATFORM_SHARED_EXT=dylib
        PLATFORM_SHARED_LDFLAGS="-dynamiclib -install_name "
-        PORT_FILE=port/port_posix.cc
+        # PORT_FILES=port/darwin/darwin_specific.cc
        ;;
    Linux)
        PLATFORM=OS_LINUX
-        COMMON_FLAGS="$COMMON_FLAGS -DOS_LINUX -fPIC"
+        COMMON_FLAGS="$COMMON_FLAGS -DOS_LINUX"
        if [ -z "$USE_CLANG" ]; then
            COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp"
        fi
        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lpthread"
-        PORT_FILE=port/port_posix.cc
+        # PORT_FILES=port/linux/linux_specific.cc
        ;;
    SunOS)
        PLATFORM=OS_SOLARIS
        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_SOLARIS"
        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lpthread -lrt"
-        PORT_FILE=port/port_posix.cc
+        # PORT_FILES=port/sunos/sunos_specific.cc
        ;;
    FreeBSD)
        PLATFORM=OS_FREEBSD
        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_FREEBSD"
        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lpthread"
-        PORT_FILE=port/port_posix.cc
+        # PORT_FILES=port/freebsd/freebsd_specific.cc
        ;;
    NetBSD)
        PLATFORM=OS_NETBSD
        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_NETBSD"
        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lpthread -lgcc_s"
-        PORT_FILE=port/port_posix.cc
+        # PORT_FILES=port/netbsd/netbsd_specific.cc
        ;;
    OpenBSD)
        PLATFORM=OS_OPENBSD
        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_OPENBSD"
        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -pthread"
-        PORT_FILE=port/port_posix.cc
+        # PORT_FILES=port/openbsd/openbsd_specific.cc
        ;;
    DragonFly)
        PLATFORM=OS_DRAGONFLYBSD
        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_DRAGONFLYBSD"
        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lpthread"
-        PORT_FILE=port/port_posix.cc
+        # PORT_FILES=port/dragonfly/dragonfly_specific.cc
        ;;
    OS_ANDROID_CROSSCOMPILE)
        PLATFORM=OS_ANDROID
 	COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_ANDROID -DLEVELDB_PLATFORM_POSIX"
 	PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS "  # All pthread features are in the Android C library
-        PORT_FILE=port/port_posix.cc
+        # PORT_FILES=port/android/android.cc
        CROSS_COMPILE=true
        ;;
    *)
@@ -130,7 +133,7 @@ esac
 # except for the test and benchmark files. By default, find will output a list
 # of all files matching either rule, so we need to append -print to make the
 # prune take effect.
-DIRS="util db table"
+DIRS="util db table utilities"
 if test "$USE_THRIFT"; then
  DIRS="$DIRS thrift/server_utils.cpp thrift/gen-cpp "
  THRIFTSERVER=leveldb_server
@@ -143,13 +146,13 @@ fi
 set -f # temporarily disable globbing so that our patterns arent expanded
 PRUNE_TEST="-name *test*.cc -prune"
 PRUNE_BENCH="-name *_bench.cc -prune"
-PORTABLE_FILES=`find $DIRS $PRUNE_TEST -o $PRUNE_BENCH -o -name '*.cc' -print | sort | tr "\n" " "`
-PORTABLE_CPP=`find $DIRS $PRUNE_TEST -o $PRUNE_BENCH -o -name '*.cpp' -print | sort | tr "\n" " "`
+PORTABLE_FILES=`cd $ROCKSDB_ROOT; find $DIRS $PRUNE_TEST -o $PRUNE_BENCH -o -name '*.cc' -print | sort | tr "\n" " "`
+PORTABLE_CPP=`cd $ROCKSDB_ROOT; find $DIRS $PRUNE_TEST -o $PRUNE_BENCH -o -name '*.cpp' -print | sort | tr "\n" " "`
 set +f # re-enable globbing

 # The sources consist of the portable files, plus the platform-specific port
 # file.
-echo "SOURCES=$PORTABLE_FILES $PORT_FILE" >> $OUTPUT
+echo "SOURCES=$PORTABLE_FILES $GENERIC_PORT_FILES $PORT_FILES" >> $OUTPUT
 echo "SOURCESCPP=$PORTABLE_CPP" >> $OUTPUT
 echo "MEMENV_SOURCES=helpers/memenv/memenv.cc" >> $OUTPUT

@@ -0,0 +1,42 @@
+#!/bin/sh
+#
+# Record the version of the source that we are compiling.
+# We keep a record of the git revision in util/version.cc. This source file
+# is then built as a regular source file as part of the compilation process.
+# One can run "strings executable_filename | grep _build_" to find the version of
+# the source that we used to build the executable file.
+#
+
+# create git version file
+VFILE=$ROCKSDB_ROOT/util/build_version.cc.tmp
+trap "rm $VFILE" EXIT
+
+# check to see if git is in the path
+which git > /dev/null
+
+if [ "$?" = 0 ]; then
+  env -i git rev-parse HEAD |
+  awk '
+  BEGIN {
+    print "#include \"build_version.h\"\n"
+  } 
+  { print "const char* leveldb_build_git_sha = \"leveldb_build_git_sha:" $0"\";" }
+  ' >  ${VFILE}
+else
+  echo "git not found" |
+  awk '
+    BEGIN {
+      print "#include \"build_version.h\"" 
+    } 
+    { print "const char* leveldb_build_git_sha = \"leveldb_build_git_sha:git not found\";" }
+    ' > ${VFILE}
+fi
+
+echo "const char* leveldb_build_git_datetime = \"leveldb_build_git_datetime:$(date)\";" >> ${VFILE}
+echo "const char* leveldb_build_compile_date = __DATE__;" >> ${VFILE}
+echo "const char* leveldb_build_compile_time = __TIME__;" >> ${VFILE}
+
+OUTFILE=$ROCKSDB_ROOT/util/build_version.cc
+if [ ! -e $OUTFILE ] || ! cmp -s $VFILE $OUTFILE; then
+    cp $VFILE $OUTFILE
+fi
@@ -4,10 +4,10 @@
 # fbcode settings.  It uses the latest g++ compiler and also
 # uses jemalloc

-TOOLCHAIN_REV=3748fabb2c5e033009597bae1f9ef8bf4b218581
+TOOLCHAIN_REV=83eb773e262fa705eaebbf3de40db71d53fabf2e
 TOOLCHAIN_EXECUTABLES="/mnt/gvfs/third-party/$TOOLCHAIN_REV/centos5.2-native"
 TOOLCHAIN_LIB_BASE="/mnt/gvfs/third-party/$TOOLCHAIN_REV/gcc-4.7.1-glibc-2.14.1"
-TOOL_JEMALLOC=jemalloc-3.0.0/2f45f3a
+TOOL_JEMALLOC=jemalloc-3.3.1/2f45f3a

 # location of libhdfs libraries
 if test "$USE_HDFS"; then
@@ -14,8 +14,8 @@ fi
 # On the production build servers, set data and stat
 # files/directories not in /tmp or else the tempdir cleaning
 # scripts will make you very unhappy.
-DATA_DIR=${DATA_DIR:-$(mktemp --tmpdir -d leveldb_XXXX)}
-STAT_FILE=${STAT_FILE:-$(mktemp --tmpdir -u leveldb_test_stats_XXXX)}
+DATA_DIR=${DATA_DIR:-$(mktemp -t -d rocksdb_XXXX)}
+STAT_FILE=${STAT_FILE:-$(mktemp -t -u rocksdb_test_stats_XXXX)}

 function cleanup {
  rm -rf $DATA_DIR
@@ -34,7 +34,8 @@ function send_to_ods {
    echo >&2 "ERROR: Key $key doesn't have a value."
    return
  fi
-  curl -s "https://www.intern.facebook.com/intern/agent/ods_set.php?entity=rocksdb_build&key=$key&value=$value"
+  curl -s "https://www.intern.facebook.com/intern/agent/ods_set.php?entity=rocksdb_build&key=$key&value=$value" \
+    --connect-timeout 60
 }

 make clean
@@ -2,10 +2,11 @@
 #A shell script for Jenknis to run valgrind on rocksdb tests
 #Returns 0 on success when there are no failed tests 

-VALGRIND_DIR=VALGRIND_LOGS
+VALGRIND_DIR=build_tools/VALGRIND_LOGS
+make clean
 make -j$(nproc) valgrind_check
 NUM_FAILED_TESTS=$((`wc -l $VALGRIND_DIR/valgrind_failed_tests | awk '{print $1}'` - 1))
-if [ $NUM_FAILED_TESTS -le 1 ]; then
+if [ $NUM_FAILED_TESTS -lt 1 ]; then
  echo No tests have valgrind errors
  exit 0
 else
@@ -0,0 +1,66 @@
+#!/bin/bash
+
+# Exit on error.
+set -e
+
+if [ -n "$USE_CLANG" ]; then
+  echo "Error: Coverage test is supported only for gcc."
+  exit 1
+fi
+
+ROOT=".."
+# Fetch right version of gcov
+if [ -d /mnt/gvfs/third-party -a -z "$CXX" ]; then
+  source $ROOT/build_tools/fbcode.gcc471.sh
+  GCOV=$TOOLCHAIN_EXECUTABLES/gcc/gcc-4.7.1/cc6c9dc/bin/gcov
+else
+  GCOV=$(which gcov)
+fi
+
+COVERAGE_DIR="$PWD/COVERAGE_REPORT"
+mkdir -p $COVERAGE_DIR
+
+# Find all gcno files to generate the coverage report
+
+GCNO_FILES=`find $ROOT -name "*.gcno"`
+$GCOV --preserve-paths --relative-only --no-output $GCNO_FILES 2>/dev/null |
+  # Parse the raw gcov report to more human readable form.
+  python $ROOT/coverage/parse_gcov_output.py |
+  # Write the output to both stdout and report file.
+  tee $COVERAGE_DIR/coverage_report_all.txt &&
+echo -e "Generated coverage report for all files: $COVERAGE_DIR/coverage_report_all.txt\n"
+
+# TODO: we also need to get the files of the latest commits.
+# Get the most recently committed files.
+LATEST_FILES=`
+  git show --pretty="format:" --name-only HEAD |
+  grep -v "^$" |
+  paste -s -d,`
+RECENT_REPORT=$COVERAGE_DIR/coverage_report_recent.txt
+
+echo -e "Recently updated files: $LATEST_FILES\n" > $RECENT_REPORT
+$GCOV --preserve-paths --relative-only --no-output $GCNO_FILES 2>/dev/null |
+  python $ROOT/coverage/parse_gcov_output.py -interested-files $LATEST_FILES |
+  tee -a $RECENT_REPORT &&
+echo -e "Generated coverage report for recently updated files: $RECENT_REPORT\n"
+
+# Generate the html report. If we cannot find lcov in this machine, we'll simply
+# skip this step.
+echo "Generating the html coverage report..."
+
+LCOV=$(which lcov || true 2>/dev/null)
+if [ -z $LCOV ]
+then
+  echo "Skip: Cannot find lcov to generate the html report."
+  exit 0
+fi
+
+(cd $ROOT; lcov --no-external \
+     --capture  \
+     --directory $PWD \
+     --gcov-tool $GCOV \
+     --output-file $COVERAGE_DIR/coverage.info &>/dev/null)
+
+genhtml $COVERAGE_DIR/coverage.info -o $COVERAGE_DIR &>/dev/null
+
+echo "HTML Coverage report is generated in $COVERAGE_DIR"
@@ -0,0 +1,118 @@
+import optparse
+import re
+import sys
+
+from optparse import OptionParser
+
+# the gcov report follows certain pattern. Each file will have two lines
+# of report, from which we can extract the file name, total lines and coverage
+# percentage.
+def parse_gcov_report(gcov_input):
+    per_file_coverage = {}
+    total_coverage = None
+
+    for line in sys.stdin:
+        line = line.strip()
+
+        # --First line of the coverage report (with file name in it)?
+        match_obj = re.match("^File '(.*)'$", line)
+        if match_obj:
+            # fetch the file name from the first line of the report.
+            current_file = match_obj.group(1)
+            continue
+
+        # -- Second line of the file report (with coverage percentage)
+        match_obj = re.match("^Lines executed:(.*)% of (.*)", line)
+
+        if match_obj:
+            coverage = float(match_obj.group(1))
+            lines = int(match_obj.group(2))
+
+            if current_file is not None:
+                per_file_coverage[current_file] = (coverage, lines)
+                current_file = None
+            else:
+                # If current_file is not set, we reach the last line of report,
+                # which contains the summarized coverage percentage.
+                total_coverage = (coverage, lines)
+            continue
+
+        # If the line's pattern doesn't fall into the above categories. We
+        # can simply ignore them since they're either empty line or doesn't
+        # find executable lines of the given file.
+        current_file = None
+
+    return per_file_coverage, total_coverage
+
+def get_option_parser():
+    usage = "Parse the gcov output and generate more human-readable code " +\
+            "coverage report."
+    parser = OptionParser(usage)
+
+    parser.add_option(
+        "--interested-files", "-i",
+        dest="filenames",
+        help="Comma separated files names. if specified, we will display " +
+             "the coverage report only for interested source files. " +
+             "Otherwise we will display the coverage report for all " +
+             "source files."
+    )
+    return parser
+
+def display_file_coverage(per_file_coverage, total_coverage):
+    # To print out auto-adjustable column, we need to know the longest
+    # length of file names.
+    max_file_name_length = max(
+        len(fname) for fname in per_file_coverage.keys()
+    )
+
+    # -- Print header
+    # size of separator is determined by 3 column sizes:
+    # file name, coverage percentage and lines.
+    header_template = \
+        "%" + str(max_file_name_length) + "s\t%s\t%s"
+    separator = "-" * (max_file_name_length + 10 + 20)
+    print header_template % ("Filename", "Coverage", "Lines")
+    print separator
+
+    # -- Print body
+    # template for printing coverage report for each file.
+    record_template = "%" + str(max_file_name_length) + "s\t%5.2f%%\t%10d"
+
+    for fname, coverage_info in per_file_coverage.items():
+        coverage, lines = coverage_info
+        print record_template % (fname, coverage, lines)
+
+    # -- Print footer
+    if total_coverage:
+        print separator
+        print record_template % ("Total", total_coverage[0], total_coverage[1])
+
+def report_coverage():
+    parser = get_option_parser()
+    (options, args) = parser.parse_args()
+
+    interested_files = set()
+    if options.filenames is not None:
+        interested_files = set(f.strip() for f in options.filenames.split(','))
+
+    # To make things simple, right now we only read gcov report from the input
+    per_file_coverage, total_coverage = parse_gcov_report(sys.stdin)
+
+    # Check if we need to display coverage info for interested files.
+    if len(interested_files):
+        per_file_coverage = dict(
+            (fname, per_file_coverage[fname]) for fname in interested_files
+            if fname in per_file_coverage
+        )
+        # If we only interested in several files, it makes no sense to report
+        # the total_coverage
+        total_coverage = None
+
+    if not len(per_file_coverage):
+        print >> sys.stderr, "Cannot find coverage info for the given files."
+        return
+    display_file_coverage(per_file_coverage, total_coverage)
+
+if __name__ == "__main__":
+    report_coverage()
@@ -6,17 +6,20 @@

 #include "db/filename.h"
 #include "db/dbformat.h"
+#include "db/merge_helper.h"
 #include "db/table_cache.h"
 #include "db/version_edit.h"
 #include "leveldb/db.h"
 #include "leveldb/env.h"
 #include "leveldb/iterator.h"
+#include "util/stop_watch.h"

 namespace leveldb {

 Status BuildTable(const std::string& dbname,
                  Env* env,
                  const Options& options,
+                  const EnvOptions& soptions,
                  TableCache* table_cache,
                  Iterator* iter,
                  FileMetaData* meta,
@@ -25,6 +28,7 @@ Status BuildTable(const std::string& dbname,
                  const SequenceNumber earliest_seqno_in_memtable) {
  Status s;
  meta->file_size = 0;
+  meta->smallest_seqno = meta->largest_seqno = 0;
  iter->SeekToFirst();

  // If the sequence number of the smallest entry in the memtable is
@@ -38,7 +42,7 @@ Status BuildTable(const std::string& dbname,
  std::string fname = TableFileName(dbname, meta->number);
  if (iter->Valid()) {
    unique_ptr<WritableFile> file;
-    s = env->NewWritableFile(fname, &file);
+    s = env->NewWritableFile(fname, &file, soptions);
    if (!s.ok()) {
      return s;
    }
@@ -47,47 +51,106 @@ Status BuildTable(const std::string& dbname,
    // the first key is the smallest key
    Slice key = iter->key();
    meta->smallest.DecodeFrom(key);
+    meta->smallest_seqno = GetInternalKeySeqno(key);
+    meta->largest_seqno = meta->smallest_seqno;
+
+    MergeHelper merge(user_comparator, options.merge_operator.get(),
+                      options.info_log.get(),
+                      true /* internal key corruption is not ok */);

    if (purge) {
+      // Ugly walkaround to avoid compiler error for release build
+      bool ok __attribute__((unused)) = true;
+
+      // Will write to builder if current key != prev key
      ParsedInternalKey prev_ikey;
-      std::string prev_value;
      std::string prev_key;
+      bool is_first_key = true;    // Also write if this is the very first key

-      // store first key-value
-      prev_key.assign(key.data(), key.size());
-      prev_value.assign(iter->value().data(), iter->value().size());
-      ParseInternalKey(Slice(prev_key), &prev_ikey);
-      assert(prev_ikey.sequence >= earliest_seqno_in_memtable);
+      while (iter->Valid()) {
+        bool iterator_at_next = false;

-      for (iter->Next(); iter->Valid(); iter->Next()) {
+        // Get current key
        ParsedInternalKey this_ikey;
        Slice key = iter->key();
-        ParseInternalKey(key, &this_ikey);
+        Slice value = iter->value();
+
+        // In-memory key corruption is not ok;
+        // TODO: find a clean way to treat in memory key corruption
+        ok = ParseInternalKey(key, &this_ikey);
+        assert(ok);
        assert(this_ikey.sequence >= earliest_seqno_in_memtable);

-        if (user_comparator->Compare(prev_ikey.user_key, this_ikey.user_key)) {
-          // This key is different from previous key.
-          // Output prev key and remember current key
-          builder->Add(Slice(prev_key), Slice(prev_value));
-          prev_key.assign(key.data(), key.size());
-          prev_value.assign(iter->value().data(), iter->value().size());
-          ParseInternalKey(Slice(prev_key), &prev_ikey);
-        } else {
+        // If the key is the same as the previous key (and it is not the
+        // first key), then we skip it, since it is an older version.
+        // Otherwise we output the key and mark it as the "new" previous key.
+        if (!is_first_key && !user_comparator->Compare(prev_ikey.user_key,
+                                                       this_ikey.user_key)) {
          // seqno within the same key are in decreasing order
          assert(this_ikey.sequence < prev_ikey.sequence);
-          // This key is an earlier version of the same key in prev_key.
-          // Skip current key.
+        } else {
+          is_first_key = false;
+
+          if (this_ikey.type == kTypeMerge) {
+            // Handle merge-type keys using the MergeHelper
+            merge.MergeUntil(iter, 0 /* don't worry about snapshot */);
+            iterator_at_next = true;
+            if (merge.IsSuccess()) {
+              // Merge completed correctly.
+              // Add the resulting merge key/value and continue to next
+              builder->Add(merge.key(), merge.value());
+              prev_key.assign(merge.key().data(), merge.key().size());
+              ok = ParseInternalKey(Slice(prev_key), &prev_ikey);
+              assert(ok);
+            } else {
+              // Merge did not find a Put/Delete.
+              // Can not compact these merges into a kValueType.
+              // Write them out one-by-one. (Proceed back() to front())
+              const std::deque<std::string>& keys = merge.keys();
+              const std::deque<std::string>& values = merge.values();
+              assert(keys.size() == values.size() && keys.size() >= 1);
+              std::deque<std::string>::const_reverse_iterator key_iter;
+              std::deque<std::string>::const_reverse_iterator value_iter;
+              for (key_iter=keys.rbegin(), value_iter = values.rbegin();
+                   key_iter != keys.rend() && value_iter != values.rend();
+                   ++key_iter, ++value_iter) {
+
+                builder->Add(Slice(*key_iter), Slice(*value_iter));
+              }
+
+              // Sanity check. Both iterators should end at the same time
+              assert(key_iter == keys.rend() && value_iter == values.rend());
+
+              prev_key.assign(keys.front());
+              ok = ParseInternalKey(Slice(prev_key), &prev_ikey);
+              assert(ok);
+            }
+          } else {
+            // Handle Put/Delete-type keys by simply writing them
+            builder->Add(key, value);
+            prev_key.assign(key.data(), key.size());
+            ok = ParseInternalKey(Slice(prev_key), &prev_ikey);
+            assert(ok);
+          }
        }
+
+        if (!iterator_at_next) iter->Next();
      }
-      // output last key
-      builder->Add(Slice(prev_key), Slice(prev_value));
+
+      // The last key is the largest key
      meta->largest.DecodeFrom(Slice(prev_key));
+      SequenceNumber seqno = GetInternalKeySeqno(Slice(prev_key));
+      meta->smallest_seqno = std::min(meta->smallest_seqno, seqno);
+      meta->largest_seqno = std::max(meta->largest_seqno, seqno);

    } else {
      for (; iter->Valid(); iter->Next()) {
        Slice key = iter->key();
        meta->largest.DecodeFrom(key);
        builder->Add(key, iter->value());
+        SequenceNumber seqno = GetInternalKeySeqno(key);
+        meta->smallest_seqno = std::min(meta->smallest_seqno, seqno);
+        meta->largest_seqno = std::max(meta->largest_seqno, seqno);
      }
    }

@@ -106,8 +169,10 @@ Status BuildTable(const std::string& dbname,
    // Finish and check for file errors
    if (s.ok() && !options.disableDataSync) {
      if (options.use_fsync) {
+        StopWatch sw(env, options.statistics, TABLE_SYNC_MICROS);
        s = file->Fsync();
      } else {
+        StopWatch sw(env, options.statistics, TABLE_SYNC_MICROS);
        s = file->Sync();
      }
    }
@@ -118,6 +183,7 @@ Status BuildTable(const std::string& dbname,
    if (s.ok()) {
      // Verify that the table is usable
      Iterator* it = table_cache->NewIterator(ReadOptions(),
+                                              soptions,
                                              meta->number,
                                              meta->file_size);
      s = it->status();
@@ -15,6 +15,7 @@ struct Options;
 struct FileMetaData;

 class Env;
+class EnvOptions;
 class Iterator;
 class TableCache;
 class VersionEdit;
@@ -27,6 +28,7 @@ class VersionEdit;
 extern Status BuildTable(const std::string& dbname,
                         Env* env,
                         const Options& options,
+                         const EnvOptions& soptions,
                         TableCache* table_cache,
                         Iterator* iter,
                         FileMetaData* meta,
@@ -10,12 +10,12 @@
 #include <sys/types.h>
 #include "leveldb/cache.h"
 #include "leveldb/env.h"
-#include "leveldb/table.h"
 #include "leveldb/write_batch.h"
 #include "db/db_impl.h"
 #include "db/filename.h"
 #include "db/log_format.h"
 #include "db/version_set.h"
+#include "table/table.h"
 #include "util/logging.h"
 #include "util/testharness.h"
 #include "util/testutil.h"
@@ -40,6 +40,7 @@ class CorruptionTest {

    db_ = nullptr;
    options_.create_if_missing = true;
+    options_.block_size_deviation = 0; // make unit test pass for now
    Reopen();
    options_.create_if_missing = false;
  }
@@ -55,6 +56,8 @@ class CorruptionTest {
    Options opt = (options ? *options : options_);
    opt.env = &env_;
    opt.block_cache = tiny_cache_;
+    opt.block_size_deviation = 0;
+    opt.arena_block_size = 4096;
    return DB::Open(opt, dbname_, &db_);
  }

@@ -2,10 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

-#include "db/db_impl.h"
-#include "db/filename.h"
+#include <algorithm>
 #include <string>
 #include <stdint.h>
+#include "db/db_impl.h"
+#include "db/filename.h"
 #include "db/version_set.h"
 #include "leveldb/db.h"
 #include "leveldb/env.h"
@@ -17,12 +18,14 @@ namespace leveldb {
 Status DBImpl::DisableFileDeletions() {
  MutexLock l(&mutex_);
  disable_delete_obsolete_files_ = true;
+  Log(options_.info_log, "File Deletions Disabled");
  return Status::OK();
 }

 Status DBImpl::EnableFileDeletions() {
  MutexLock l(&mutex_);
  disable_delete_obsolete_files_ = false;
+  Log(options_.info_log, "File Deletions Enabled");
  return Status::OK();
 }

@@ -64,4 +67,47 @@ Status DBImpl::GetLiveFiles(std::vector<std::string>& ret,
  return Status::OK();
 }

+Status DBImpl::GetSortedWalFiles(VectorLogPtr& files) {
+  // First get sorted files in archive dir, then append sorted files from main
+  // dir to maintain sorted order
+
+  //  list wal files in archive dir.
+  Status s;
+  std::string archivedir = ArchivalDirectory(dbname_);
+  if (env_->FileExists(archivedir)) {
+    s = AppendSortedWalsOfType(archivedir, files, kArchivedLogFile);
+    if (!s.ok()) {
+      return s;
+    }
+  }
+  // list wal files in main db dir.
+  s = AppendSortedWalsOfType(dbname_, files, kAliveLogFile);
+  if (!s.ok()) {
+    return s;
+  }
+  return s;
+}
+
+Status DBImpl::DeleteWalFiles(const VectorLogPtr& files) {
+  Status s;
+  std::string archivedir = ArchivalDirectory(dbname_);
+  std::string files_not_deleted;
+  for (const auto& wal : files) {
+    /* Try deleting in archive dir. If fails, try deleting in main db dir.
+     * This is efficient because all except for very few wal files will be in
+     * archive. Checking for WalType is not much helpful because alive wal could
+       be archived now.
+     */
+    if (!env_->DeleteFile(archivedir + "/" + wal->Filename()).ok() &&
+        !env_->DeleteFile(dbname_ + "/" + wal->Filename()).ok()) {
+      files_not_deleted.append(wal->Filename());
+    }
+  }
+  if (!files_not_deleted.empty()) {
+    return Status::IOError("Deleted all requested files except: " +
+                           files_not_deleted);
+  }
+  return Status::OK();
+}
+
 }
@@ -5,14 +5,17 @@
 #ifndef STORAGE_LEVELDB_DB_DB_IMPL_H_
 #define STORAGE_LEVELDB_DB_DB_IMPL_H_

+#include <atomic>
 #include <deque>
 #include <set>
+#include <vector>
 #include "db/dbformat.h"
-#include "db/log_file.h"
 #include "db/log_writer.h"
 #include "db/snapshot.h"
 #include "leveldb/db.h"
 #include "leveldb/env.h"
+#include "leveldb/memtablerep.h"
+#include "leveldb/transaction_log.h"
 #include "port/port.h"
 #include "util/stats_logger.h"
 #include "memtablelist.h"
@@ -36,17 +39,32 @@ class DBImpl : public DB {

  // Implementations of the DB interface
  virtual Status Put(const WriteOptions&, const Slice& key, const Slice& value);
+  virtual Status Merge(const WriteOptions&, const Slice& key,
+                       const Slice& value);
  virtual Status Delete(const WriteOptions&, const Slice& key);
  virtual Status Write(const WriteOptions& options, WriteBatch* updates);
  virtual Status Get(const ReadOptions& options,
                     const Slice& key,
                     std::string* value);
+  virtual std::vector<Status> MultiGet(const ReadOptions& options,
+                                       const std::vector<Slice>& keys,
+                                       std::vector<std::string>* values);
+
+  // Returns false if key doesn't exist in the database and true if it may.
+  // If value_found is not passed in as null, then return the value if found in
+  // memory. On return, if value was found, then value_found will be set to true
+  // , otherwise false.
+  virtual bool KeyMayExist(const ReadOptions& options,
+                           const Slice& key,
+                           std::string* value,
+                           bool* value_found = nullptr);
  virtual Iterator* NewIterator(const ReadOptions&);
  virtual const Snapshot* GetSnapshot();
  virtual void ReleaseSnapshot(const Snapshot* snapshot);
  virtual bool GetProperty(const Slice& property, std::string* value);
  virtual void GetApproximateSizes(const Range* range, int n, uint64_t* sizes);
-  virtual void CompactRange(const Slice* begin, const Slice* end);
+  virtual void CompactRange(const Slice* begin, const Slice* end,
+                            bool reduce_level = false);
  virtual int NumberLevels();
  virtual int MaxMemCompactionLevel();
  virtual int Level0StopWriteTrigger();
@@ -55,13 +73,15 @@ class DBImpl : public DB {
  virtual Status EnableFileDeletions();
  virtual Status GetLiveFiles(std::vector<std::string>&,
                              uint64_t* manifest_file_size);
+  virtual Status GetSortedWalFiles(VectorLogPtr& files);
+  virtual Status DeleteWalFiles(const VectorLogPtr& files);
  virtual SequenceNumber GetLatestSequenceNumber();
  virtual Status GetUpdatesSince(SequenceNumber seq_number,
                                 unique_ptr<TransactionLogIterator>* iter);

  // Extra methods (for testing) that are not in the public DB interface

-  // Compact any files in the named level that overlap [*begin,*end]
+  // Compact any files in the named level that overlap [*begin, *end]
  void TEST_CompactRange(int level, const Slice* begin, const Slice* end);

  // Force current memtable contents to be compacted.
@@ -87,6 +107,10 @@ class DBImpl : public DB {

  // Return the current manifest file no.
  uint64_t TEST_Current_Manifest_FileNo();
+
+  // Trigger's a background call for testing.
+  void TEST_PurgeObsoleteteWAL();
+
 protected:
  Env* const env_;
  const std::string dbname_;
@@ -141,9 +165,10 @@ class DBImpl : public DB {
  // for the entire period. The second method WriteLevel0Table supports
  // concurrent flush memtables to storage.
  Status WriteLevel0TableForRecovery(MemTable* mem, VersionEdit* edit);
-  Status WriteLevel0Table(MemTable* mem, VersionEdit* edit,
+  Status WriteLevel0Table(std::vector<MemTable*> &mems, VersionEdit* edit,
                                uint64_t* filenumber);

+  uint64_t SlowdownAmount(int n, int top, int bottom);
  Status MakeRoomForWrite(bool force /* compact even if there is room? */);
  WriteBatch* BuildBatchGroup(Writer** last_writer);

@@ -160,7 +185,7 @@ class DBImpl : public DB {
  void MaybeScheduleCompaction();
  static void BGWork(void* db);
  void BackgroundCall();
-  Status BackgroundCompaction(bool* madeProgress, DeletionState& deletion_state);
+  Status BackgroundCompaction(bool* madeProgress,DeletionState& deletion_state);
  void CleanupCompaction(CompactionState* compact);
  Status DoCompactionWork(CompactionState* compact);

@@ -185,21 +210,37 @@ class DBImpl : public DB {

  void PurgeObsoleteWALFiles();

-  Status ListAllWALFiles(const std::string& path,
-                         std::vector<LogFile>* logFiles,
-                         WalFileType type);
+  Status AppendSortedWalsOfType(const std::string& path,
+                                VectorLogPtr& log_files,
+                                WalFileType type);

-  //  Find's all the log files which contain updates with seq no.
-  //  Greater Than or Equal to the requested SequenceNumber
-  Status FindProbableWALFiles(std::vector<LogFile>* const allLogs,
-                              std::vector<LogFile>* const result,
-                              const SequenceNumber target);
-
-
-  Status ReadFirstRecord(const LogFile& file, WriteBatch* const result);
+  // Requires: all_logs should be sorted with earliest log file first
+  // Retains all log files in all_logs which contain updates with seq no.
+  // Greater Than or Equal to the requested SequenceNumber.
+  Status RetainProbableWalFiles(VectorLogPtr& all_logs,
+                                const SequenceNumber target);
+  //  return true if
+  bool CheckWalFileExistsAndEmpty(const WalFileType type,
+                                  const uint64_t number);

+  Status ReadFirstRecord(const WalFileType type, const uint64_t number,
+                         WriteBatch* const result);

  Status ReadFirstLine(const std::string& fname, WriteBatch* const batch);
+
+  void PrintStatistics();
+
+  // dump leveldb.stats to LOG
+  void MaybeDumpStats();
+
+  // Return the minimum empty level that could hold the total data in the
+  // input level. Return the input level, if such level could not be found.
+  int FindMinimumEmptyLevelFitting(int level);
+
+  // Move the files in the input level to the minimum level that could hold
+  // the data set.
+  void ReFitLevel(int level);
+
  // Constant after construction
  const InternalFilterPolicy internal_filter_policy_;
  bool owns_info_log_;
@@ -214,6 +255,7 @@ class DBImpl : public DB {
  port::Mutex mutex_;
  port::AtomicPointer shutting_down_;
  port::CondVar bg_cv_;          // Signalled when background work finishes
+  std::shared_ptr<MemTableRepFactory> mem_rep_factory_;
  MemTable* mem_;
  MemTableList imm_;             // Memtable that are not changing
  uint64_t logfile_number_;
@@ -223,7 +265,7 @@ class DBImpl : public DB {

  // Queue of writers.
  std::deque<Writer*> writers_;
-  WriteBatch* tmp_batch_;
+  WriteBatch tmp_batch_;

  SnapshotList snapshots_;

@@ -251,7 +293,7 @@ class DBImpl : public DB {
  // Have we encountered a background error in paranoid mode?
  Status bg_error_;

-  StatsLogger* logger_;
+  std::unique_ptr<StatsLogger> logger_;

  int64_t volatile last_log_ts;

@@ -261,11 +303,21 @@ class DBImpl : public DB {
  // last time when DeleteObsoleteFiles was invoked
  uint64_t delete_obsolete_files_last_run_;

+  // last time when PurgeObsoleteWALFiles ran.
+  uint64_t purge_wal_files_last_run_;
+
+  // last time stats were dumped to LOG
+  std::atomic<uint64_t> last_stats_dump_time_microsec_;
+
  // These count the number of microseconds for which MakeRoomForWrite stalls.
  uint64_t stall_level0_slowdown_;
  uint64_t stall_memtable_compaction_;
  uint64_t stall_level0_num_files_;
  std::vector<uint64_t> stall_leveln_slowdown_;
+  uint64_t stall_level0_slowdown_count_;
+  uint64_t stall_memtable_compaction_count_;
+  uint64_t stall_level0_num_files_count_;
+  std::vector<uint64_t> stall_leveln_slowdown_count_;

  // Time at which this instance was started.
  const uint64_t started_at_;
@@ -315,7 +367,20 @@ class DBImpl : public DB {
    }
  };

-  CompactionStats* stats_;
+  std::vector<CompactionStats> stats_;
+
+  // Used to compute per-interval statistics
+  struct StatsSnapshot {
+    uint64_t bytes_read_;
+    uint64_t bytes_written_;
+    uint64_t bytes_new_;
+    double   seconds_up_;
+
+    StatsSnapshot() : bytes_read_(0), bytes_written_(0),
+                      bytes_new_(0), seconds_up_(0) {}
+  };
+
+  StatsSnapshot last_stats_;

  static const int KEEP_LOG_FILE_NUM = 1000;
  std::string db_absolute_path_;
@@ -327,6 +392,15 @@ class DBImpl : public DB {
  // Used by transaction log iterator.
  SequenceNumber last_flushed_sequence_;

+  // The options to access storage files
+  const EnvOptions storage_options_;
+
+  // A value of true temporarily disables scheduling of background work
+  bool bg_work_gate_closed_;
+
+  // Guard against multiple concurrent refitting
+  bool refitting_level_;
+
  // No copying allowed
  DBImpl(const DBImpl&);
  void operator=(const DBImpl&);
@@ -334,9 +408,20 @@ class DBImpl : public DB {
  // dump the delayed_writes_ to the log file and reset counter.
  void DelayLoggingAndReset();

-  // find the earliest snapshot where seqno is visible
-  inline SequenceNumber findEarliestVisibleSnapshot(SequenceNumber in,
-    std::vector<SequenceNumber>& snapshots);
+  // Return the earliest snapshot where seqno is visible.
+  // Store the snapshot right before that, if any, in prev_snapshot
+  inline SequenceNumber findEarliestVisibleSnapshot(
+    SequenceNumber in,
+    std::vector<SequenceNumber>& snapshots,
+    SequenceNumber* prev_snapshot);
+
+  // Function that Get and KeyMayExist call with no_io true or false
+  // Note: 'value_found' from KeyMayExist propagates here
+  Status GetImpl(const ReadOptions& options,
+                 const Slice& key,
+                 std::string* value,
+                 const bool no_io = false,
+                 bool* value_found = nullptr);
 };

 // Sanitize db options.  The caller should delete result.info_log if
@@ -24,11 +24,11 @@
 #include "leveldb/db.h"
 #include "leveldb/env.h"
 #include "leveldb/status.h"
-#include "leveldb/table.h"
 #include "leveldb/table_builder.h"
 #include "port/port.h"
 #include "table/block.h"
 #include "table/merger.h"
+#include "table/table.h"
 #include "table/two_level_iterator.h"
 #include "util/coding.h"
 #include "util/logging.h"
@@ -53,11 +53,12 @@ Status DBImplReadOnly::Get(const ReadOptions& options,
  MemTable* mem = GetMemTable();
  Version* current = versions_->current();
  SequenceNumber snapshot = versions_->LastSequence();
+  std::deque<std::string> merge_operands;
  LookupKey lkey(key, snapshot);
-  if (mem->Get(lkey, value, &s)) {
+  if (mem->Get(lkey, value, &s, &merge_operands, options_)) {
  } else {
    Version::GetStats stats;
-    s = current->Get(options, lkey, value, &stats);
+    current->Get(options, lkey, value, &s, &merge_operands, &stats, options_);
  }
  return s;
 }
@@ -66,7 +67,7 @@ Iterator* DBImplReadOnly::NewIterator(const ReadOptions& options) {
  SequenceNumber latest_snapshot;
  Iterator* internal_iter = NewInternalIterator(options, &latest_snapshot);
  return NewDBIterator(
-      &dbname_, env_, user_comparator(), internal_iter,
+    &dbname_, env_, options_,  user_comparator(),internal_iter,
      (options.snapshot != nullptr
      ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
      : latest_snapshot));
@@ -32,18 +32,26 @@ public:
 virtual Status Get(const ReadOptions& options,
                    const Slice& key,
                    std::string* value);
+
+ // TODO: Implement ReadOnly MultiGet?
+
 virtual Iterator* NewIterator(const ReadOptions&);

 virtual Status Put(const WriteOptions&, const Slice& key, const Slice& value) {
   return Status::NotSupported("Not supported operation in read only mode.");
 }
+ virtual Status Merge(const WriteOptions&, const Slice& key,
+                      const Slice& value) {
+   return Status::NotSupported("Not supported operation in read only mode.");
+ }
 virtual Status Delete(const WriteOptions&, const Slice& key) {
   return Status::NotSupported("Not supported operation in read only mode.");
 }
 virtual Status Write(const WriteOptions& options, WriteBatch* updates) {
   return Status::NotSupported("Not supported operation in read only mode.");
 }
- virtual void CompactRange(const Slice* begin, const Slice* end) {
+ virtual void CompactRange(const Slice* begin, const Slice* end,
+                           bool reduce_level = false) {
 }
 virtual Status DisableFileDeletions() {
   return Status::NotSupported("Not supported operation in read only mode.");
@@ -3,11 +3,15 @@
 // found in the LICENSE file. See the AUTHORS file for names of contributors.

 #include "db/db_iter.h"
+#include <stdexcept>
+#include <deque>

 #include "db/filename.h"
 #include "db/dbformat.h"
 #include "leveldb/env.h"
+#include "leveldb/options.h"
 #include "leveldb/iterator.h"
+#include "leveldb/merge_operator.h"
 #include "port/port.h"
 #include "util/logging.h"
 #include "util/mutexlock.h"
@@ -36,6 +40,7 @@ namespace {
 // numbers, deletion markers, overwrites, etc.
 class DBIter: public Iterator {
 public:
+  // The following is grossly complicated. TODO: clean it up
  // Which direction is the iterator currently moving?
  // (1) When moving forward, the internal iterator is positioned at
  //     the exact entry that yields this->key(), this->value()
@@ -46,27 +51,34 @@ class DBIter: public Iterator {
    kReverse
  };

-  DBIter(const std::string* dbname, Env* env,
+  DBIter(const std::string* dbname, Env* env, const Options& options,
         const Comparator* cmp, Iterator* iter, SequenceNumber s)
      : dbname_(dbname),
        env_(env),
+        logger_(options.info_log),
        user_comparator_(cmp),
+        user_merge_operator_(options.merge_operator.get()),
        iter_(iter),
        sequence_(s),
        direction_(kForward),
-        valid_(false) {
+        valid_(false),
+        current_entry_is_merged_(false),
+        statistics_(options.statistics) {
+    RecordTick(statistics_, NO_ITERATORS, 1);
  }
  virtual ~DBIter() {
+    RecordTick(statistics_, NO_ITERATORS, -1);
    delete iter_;
  }
  virtual bool Valid() const { return valid_; }
  virtual Slice key() const {
    assert(valid_);
-    return (direction_ == kForward) ? ExtractUserKey(iter_->key()) : saved_key_;
+    return saved_key_;
  }
  virtual Slice value() const {
    assert(valid_);
-    return (direction_ == kForward) ? iter_->value() : saved_value_;
+    return (direction_ == kForward && !current_entry_is_merged_) ?
+      iter_->value() : saved_value_;
  }
  virtual Status status() const {
    if (status_.ok()) {
@@ -83,9 +95,10 @@ class DBIter: public Iterator {
  virtual void SeekToLast();

 private:
-  void FindNextUserEntry(bool skipping, std::string* skip);
+  void FindNextUserEntry(bool skipping);
  void FindPrevUserEntry();
  bool ParseKey(ParsedInternalKey* key);
+  void MergeValuesNewToOld();

  inline void SaveKey(const Slice& k, std::string* dst) {
    dst->assign(k.data(), k.size());
@@ -102,15 +115,20 @@ class DBIter: public Iterator {

  const std::string* const dbname_;
  Env* const env_;
+  shared_ptr<Logger> logger_;
  const Comparator* const user_comparator_;
+  const MergeOperator* const user_merge_operator_;
  Iterator* const iter_;
  SequenceNumber const sequence_;

  Status status_;
  std::string saved_key_;     // == current key when direction_==kReverse
  std::string saved_value_;   // == current raw value when direction_==kReverse
+  std::string skip_key_;
  Direction direction_;
  bool valid_;
+  bool current_entry_is_merged_;
+  std::shared_ptr<Statistics> statistics_;

  // No copying allowed
  DBIter(const DBIter&);
@@ -120,6 +138,8 @@ class DBIter: public Iterator {
 inline bool DBIter::ParseKey(ParsedInternalKey* ikey) {
  if (!ParseInternalKey(iter_->key(), ikey)) {
    status_ = Status::Corruption("corrupted internal key in DBIter");
+    Log(logger_, "corrupted internal key in DBIter: %s",
+        iter_->key().ToString(true).c_str());
    return false;
  } else {
    return true;
@@ -146,47 +166,156 @@ void DBIter::Next() {
    }
  }

-  // Temporarily use saved_key_ as storage for key to skip.
-  std::string* skip = &saved_key_;
-  SaveKey(ExtractUserKey(iter_->key()), skip);
-  FindNextUserEntry(true, skip);
+  // If the current value is merged, we might already hit end of iter_
+  if (!iter_->Valid()) {
+    valid_ = false;
+    return;
+  }
+  FindNextUserEntry(true /* skipping the current user key */);
 }

-void DBIter::FindNextUserEntry(bool skipping, std::string* skip) {
+
+// PRE: saved_key_ has the current user key if skipping
+// POST: saved_key_ should have the next user key if valid_,
+//       if the current entry is a result of merge
+//           current_entry_is_merged_ => true
+//           saved_value_             => the merged value
+//
+// NOTE: In between, saved_key_ can point to a user key that has
+//       a delete marker
+void DBIter::FindNextUserEntry(bool skipping) {
  // Loop until we hit an acceptable entry to yield
  assert(iter_->Valid());
  assert(direction_ == kForward);
+  current_entry_is_merged_ = false;
  do {
    ParsedInternalKey ikey;
    if (ParseKey(&ikey) && ikey.sequence <= sequence_) {
-      switch (ikey.type) {
-        case kTypeDeletion:
-          // Arrange to skip all upcoming entries for this key since
-          // they are hidden by this deletion.
-          SaveKey(ikey.user_key, skip);
-          skipping = true;
-          break;
-        case kTypeValue:
-          if (skipping &&
-              user_comparator_->Compare(ikey.user_key, *skip) <= 0) {
-            // Entry hidden
-          } else {
+      if (skipping &&
+          user_comparator_->Compare(ikey.user_key, saved_key_) <= 0) {
+        // skip this entry
+      } else {
+        skipping = false;
+        switch (ikey.type) {
+          case kTypeDeletion:
+            // Arrange to skip all upcoming entries for this key since
+            // they are hidden by this deletion.
+            SaveKey(ikey.user_key, &saved_key_);
+            skipping = true;
+            break;
+          case kTypeValue:
            valid_ = true;
-            saved_key_.clear();
+            SaveKey(ikey.user_key, &saved_key_);
            return;
-          }
-          break;
+          case kTypeMerge:
+            // By now, we are sure the current ikey is going to yield a value
+            SaveKey(ikey.user_key, &saved_key_);
+            current_entry_is_merged_ = true;
+            valid_ = true;
+            MergeValuesNewToOld();  // Go to a different state machine
+            return;
+          case kTypeLogData:
+            assert(false);
+            break;
+        }
      }
    }
    iter_->Next();
  } while (iter_->Valid());
-  saved_key_.clear();
  valid_ = false;
 }

+// Merge values of the same user key starting from the current iter_ position
+// Scan from the newer entries to older entries.
+// PRE: iter_->key() points to the first merge type entry
+//      saved_key_ stores the user key
+// POST: saved_value_ has the merged value for the user key
+//       iter_ points to the next entry (or invalid)
+void DBIter::MergeValuesNewToOld() {
+  if (!user_merge_operator_) {
+    Log(logger_, "Options::merge_operator is null.");
+    throw std::logic_error("DBIter::MergeValuesNewToOld() with"
+                           " Options::merge_operator null");
+  }
+
+  // Start the merge process by pushing the first operand
+  std::deque<std::string> operands;
+  operands.push_front(iter_->value().ToString());
+
+  std::string merge_result;   // Temporary string to hold merge result later
+  ParsedInternalKey ikey;
+  for (iter_->Next(); iter_->Valid(); iter_->Next()) {
+    if (!ParseKey(&ikey)) {
+      // skip corrupted key
+      continue;
+    }
+
+    if (user_comparator_->Compare(ikey.user_key, saved_key_) != 0) {
+      // hit the next user key, stop right here
+      break;
+    }
+
+    if (kTypeDeletion == ikey.type) {
+      // hit a delete with the same user key, stop right here
+      // iter_ is positioned after delete
+      iter_->Next();
+      break;
+    }
+
+    if (kTypeValue == ikey.type) {
+      // hit a put, merge the put value with operands and store the
+      // final result in saved_value_. We are done!
+      // ignore corruption if there is any.
+      const Slice value = iter_->value();
+      user_merge_operator_->FullMerge(ikey.user_key, &value, operands,
+                                      &saved_value_, logger_.get());
+      // iter_ is positioned after put
+      iter_->Next();
+      return;
+    }
+
+    if (kTypeMerge == ikey.type) {
+      // hit a merge, add the value as an operand and run associative merge.
+      // when complete, add result to operands and continue.
+      const Slice& value = iter_->value();
+      operands.push_front(value.ToString());
+      while(operands.size() >= 2) {
+        // Call user associative-merge until it returns false
+        if (user_merge_operator_->PartialMerge(ikey.user_key,
+                                               Slice(operands[0]),
+                                               Slice(operands[1]),
+                                               &merge_result,
+                                               logger_.get())) {
+          operands.pop_front();
+          swap(operands.front(), merge_result);
+        } else {
+          // Associative merge returns false ==> stack the operands
+          break;
+        }
+      }
+
+    }
+  }
+
+  // we either exhausted all internal keys under this user key, or hit
+  // a deletion marker.
+  // feed null as the existing value to the merge operator, such that
+  // client can differentiate this scenario and do things accordingly.
+  user_merge_operator_->FullMerge(saved_key_, nullptr, operands,
+                                  &saved_value_, logger_.get());
+}
+
 void DBIter::Prev() {
  assert(valid_);

+  // Throw an exception now if merge_operator is provided
+  // TODO: support backward iteration
+  if (user_merge_operator_) {
+    Log(logger_, "Prev not supported yet if merge_operator is provided");
+    throw std::logic_error("DBIter::Prev backward iteration not supported"
+                           " if merge_operator is provided");
+  }
+
  if (direction_ == kForward) {  // Switch directions?
    // iter_ is pointing at the current entry.  Scan backwards until
    // the key changes so we can use the normal reverse scanning code.
@@ -261,7 +390,7 @@ void DBIter::Seek(const Slice& target) {
      &saved_key_, ParsedInternalKey(target, sequence_, kValueTypeForSeek));
  iter_->Seek(saved_key_);
  if (iter_->Valid()) {
-    FindNextUserEntry(false, &saved_key_ /* temporary storage */);
+    FindNextUserEntry(false /*not skipping */);
  } else {
    valid_ = false;
  }
@@ -272,13 +401,21 @@ void DBIter::SeekToFirst() {
  ClearSavedValue();
  iter_->SeekToFirst();
  if (iter_->Valid()) {
-    FindNextUserEntry(false, &saved_key_ /* temporary storage */);
+    FindNextUserEntry(false /* not skipping */);
  } else {
    valid_ = false;
  }
 }

 void DBIter::SeekToLast() {
+  // Throw an exception for now if merge_operator is provided
+  // TODO: support backward iteration
+  if (user_merge_operator_) {
+    Log(logger_, "SeekToLast not supported yet if merge_operator is provided");
+    throw std::logic_error("DBIter::SeekToLast: backward iteration not"
+                           " supported if merge_operator is provided");
+  }
+
  direction_ = kReverse;
  ClearSavedValue();
  iter_->SeekToLast();
@@ -290,10 +427,12 @@ void DBIter::SeekToLast() {
 Iterator* NewDBIterator(
    const std::string* dbname,
    Env* env,
-    const Comparator* user_key_comparator,
+    const Options& options,
+    const Comparator *user_key_comparator,
    Iterator* internal_iter,
    const SequenceNumber& sequence) {
-  return new DBIter(dbname, env, user_key_comparator, internal_iter, sequence);
+  return new DBIter(dbname, env, options, user_key_comparator,
+                    internal_iter, sequence);
 }

 }  // namespace leveldb
@@ -17,7 +17,8 @@ namespace leveldb {
 extern Iterator* NewDBIterator(
    const std::string* dbname,
    Env* env,
-    const Comparator* user_key_comparator,
+    const Options& options,
+    const Comparator *user_key_comparator,
    Iterator* internal_iter,
    const SequenceNumber& sequence);

@@ -8,6 +8,7 @@
 #include <cassert>
 #include <stdlib.h>
 #include <vector>
+#include <memory>

 #include "leveldb/statistics.h"
 #include "util/histogram.h"
@@ -29,6 +30,11 @@ class DBStatistics: public Statistics {
    return allTickers_[tickerType].getCount();
  }

+  virtual void setTickerCount(Tickers tickerType, uint64_t count) {
+    assert(tickerType < TICKER_ENUM_MAX);
+    allTickers_[tickerType].setTickerCount(count);
+  }
+
  virtual void recordTick(Tickers tickerType, uint64_t count) {
    assert(tickerType < TICKER_ENUM_MAX);
    allTickers_[tickerType].recordTick(count);
@@ -39,11 +45,6 @@ class DBStatistics: public Statistics {
    allHistograms_[histogramType].Add(value);
  }

-  virtual void measureTime(Histograms histogramType, double value) {
-    assert(histogramType < HISTOGRAM_ENUM_MAX);
-    allHistograms_[histogramType].Add(value);
-  }
-
  virtual void histogramData(Histograms histogramType,
                             HistogramData * const data) {
    assert(histogramType < HISTOGRAM_ENUM_MAX);
@@ -53,6 +54,11 @@ class DBStatistics: public Statistics {
  std::vector<Ticker> allTickers_;
  std::vector<HistogramImpl> allHistograms_;
 };
+
+std::shared_ptr<Statistics> CreateDBStatistics() {
+  return std::make_shared<DBStatistics>();
+}
+
 } // namespace leveldb

 #endif // LEVELDB_STORAGE_DB_DB_STATISTICS_H_
@@ -6,6 +6,7 @@
 #include "db/dbformat.h"
 #include "port/port.h"
 #include "util/coding.h"
+#include "include/leveldb/perf_context.h"

 namespace leveldb {

@@ -44,7 +45,7 @@ std::string InternalKey::DebugString(bool hex) const {
 }

 const char* InternalKeyComparator::Name() const {
-  return "leveldb.InternalKeyComparator";
+  return name_.c_str();
 }

 int InternalKeyComparator::Compare(const Slice& akey, const Slice& bkey) const {
@@ -53,6 +54,7 @@ int InternalKeyComparator::Compare(const Slice& akey, const Slice& bkey) const {
  //    decreasing sequence number
  //    decreasing type (though sequence# should be enough to disambiguate)
  int r = user_comparator_->Compare(ExtractUserKey(akey), ExtractUserKey(bkey));
+  perf_context.user_key_comparison_count++;
  if (r == 0) {
    const uint64_t anum = DecodeFixed64(akey.data() + akey.size() - 8);
    const uint64_t bnum = DecodeFixed64(bkey.data() + bkey.size() - 8);
@@ -24,7 +24,9 @@ class InternalKey;
 // data structures.
 enum ValueType {
  kTypeDeletion = 0x0,
-  kTypeValue = 0x1
+  kTypeValue = 0x1,
+  kTypeMerge = 0x2,
+  kTypeLogData = 0x3
 };
 // kValueTypeForSeek defines the ValueType that should be passed when
 // constructing a ParsedInternalKey object for seeking to a particular
@@ -32,7 +34,7 @@ enum ValueType {
 // and the value type is embedded as the low 8 bits in the sequence
 // number in internal keys, we need to use the highest-numbered
 // ValueType, not the lowest).
-static const ValueType kValueTypeForSeek = kTypeValue;
+static const ValueType kValueTypeForSeek = kTypeMerge;

 // We leave eight bits empty at the bottom so a type and sequence#
 // can be packed together into 64-bits.
@@ -85,8 +87,13 @@ inline ValueType ExtractValueType(const Slice& internal_key) {
 class InternalKeyComparator : public Comparator {
 private:
  const Comparator* user_comparator_;
+  std::string name_;
 public:
-  explicit InternalKeyComparator(const Comparator* c) : user_comparator_(c) { }
+  explicit InternalKeyComparator(const Comparator* c) : user_comparator_(c),
+    name_("leveldb.InternalKeyComparator:" +
+          std::string(user_comparator_->Name())) {
+  }
+
  virtual const char* Name() const;
  virtual int Compare(const Slice& a, const Slice& b) const;
  virtual void FindShortestSeparator(
@@ -154,7 +161,7 @@ inline bool ParseInternalKey(const Slice& internal_key,
  result->sequence = num >> 8;
  result->type = static_cast<ValueType>(c);
  result->user_key = Slice(internal_key.data(), n - 8);
-  return (c <= static_cast<unsigned char>(kTypeValue));
+  return (c <= static_cast<unsigned char>(kValueTypeForSeek));
 }

 // Update the sequence number in the internal key
@@ -167,6 +174,15 @@ inline void UpdateInternalKey(char* internal_key,
  EncodeFixed64(seqtype, newval);
 }

+// Get the sequence number from the internal key
+inline uint64_t GetInternalKeySeqno(const Slice& internal_key) {
+  const size_t n = internal_key.size();
+  assert(n >= 8);
+  uint64_t num = DecodeFixed64(internal_key.data() + n - 8);
+  return num >> 8;
+}
+
+
 // A helper class useful for DBImpl::Get()
 class LookupKey {
 public:
@@ -46,10 +46,13 @@ extern Status WriteStringToFileSync(Env* env, const Slice& data,
 static std::string MakeFileName(const std::string& name, uint64_t number,
                                const char* suffix) {
  char buf[100];
-  snprintf(buf, sizeof(buf), "/%06llu.%s",
+  snprintf(buf, sizeof(buf), "%06llu.%s",
           static_cast<unsigned long long>(number),
           suffix);
-  return name + buf;
+  if (name.empty()) {
+    return buf;
+  }
+  return name + "/" + buf;
 }

 std::string LogFileName(const std::string& name, uint64_t number) {
@@ -1,48 +0,0 @@
-// Copyright 2008-present Facebook. All Rights Reserved.
-
-#ifndef STORAGE_LEVELDB_DB_LOG_FILE_H_
-#define STORAGE_LEVELDB_DB_LOG_FILE_H_
-
-namespace leveldb {
-
-enum  WalFileType {
-  kArchivedLogFile = 0,
-  kAliveLogFile = 1
-} ;
-
-class LogFile {
-
- public:
-  uint64_t logNumber;
-  WalFileType type;
-
-  LogFile(uint64_t logNum,WalFileType logType) :
-    logNumber(logNum),
-    type(logType) {}
-
-  LogFile(const LogFile& that) {
-   logNumber = that.logNumber;
-   type = that.type;
-  }
-
-  bool operator < (const LogFile& that) const {
-    return logNumber < that.logNumber;
-  }
-
-  std::string ToString() const {
-    char response[100];
-    const char* typeOfLog;
-    if (type == kAliveLogFile) {
-      typeOfLog = "Alive Log";
-    } else {
-      typeOfLog = "Archived Log";
-    }
-    sprintf(response,
-            "LogNumber  : %ld LogType : %s",
-            logNumber,
-            typeOfLog);
-    return std::string(response);
-  }
-};
-}  //  namespace leveldb
-#endif  // STORAGE_LEVELDB_DB_LOG_FILE_H_
@@ -24,7 +24,7 @@ enum RecordType {
 };
 static const int kMaxRecordType = kLastType;

-static const int kBlockSize = 32768;
+static const unsigned int kBlockSize = 32768;

 // Header is checksum (4 bytes), type (1 byte), length (2 bytes).
 static const int kHeaderSize = 4 + 1 + 2;
@@ -59,6 +59,17 @@ class Reader {
  // Undefined before the first call to ReadRecord.
  uint64_t LastRecordOffset();

+  // returns true if the reader has encountered an eof condition.
+  bool IsEOF() {
+    return eof_;
+  }
+
+  // when we know more data has been written to the file. we can use this
+  // function to force the reader to look again in the file.
+  void UnmarkEOF() {
+    eof_ = false;
+  }
+
  SequentialFile* file() { return file_.get(); }

 private:
@@ -450,13 +450,13 @@ TEST(LogTest, ErrorJoinsRecords) {
  Write("correct");

  // Wipe the middle block
-  for (int offset = kBlockSize; offset < 2*kBlockSize; offset++) {
+  for (unsigned int offset = kBlockSize; offset < 2*kBlockSize; offset++) {
    SetByte(offset, 'x');
  }

  ASSERT_EQ("correct", Read());
  ASSERT_EQ("EOF", Read());
-  const int dropped = DroppedBytes();
+  const unsigned int dropped = DroppedBytes();
  ASSERT_LE(dropped, 2*kBlockSize + 100);
  ASSERT_GE(dropped, 2*kBlockSize);
 }
@@ -3,10 +3,14 @@
 // found in the LICENSE file. See the AUTHORS file for names of contributors.

 #include "db/memtable.h"
+
+#include <memory>
+
 #include "db/dbformat.h"
 #include "leveldb/comparator.h"
 #include "leveldb/env.h"
 #include "leveldb/iterator.h"
+#include "leveldb/merge_operator.h"
 #include "util/coding.h"

 namespace leveldb {
@@ -18,22 +22,28 @@ static Slice GetLengthPrefixedSlice(const char* data) {
  return Slice(p, len);
 }

-MemTable::MemTable(const InternalKeyComparator& cmp, int numlevel)
+MemTable::MemTable(const InternalKeyComparator& cmp,
+                   std::shared_ptr<MemTableRepFactory> table_factory,
+                   int numlevel,
+                   const Options& options)
    : comparator_(cmp),
      refs_(0),
-      table_(comparator_, &arena_),
+      arena_impl_(options.arena_block_size),
+      table_(table_factory->CreateMemTableRep(comparator_, &arena_impl_)),
      flush_in_progress_(false),
      flush_completed_(false),
      file_number_(0),
      edit_(numlevel),
-      first_seqno_(0) {
-}
+      first_seqno_(0),
+      mem_logfile_number_(0) { }

 MemTable::~MemTable() {
  assert(refs_ == 0);
 }

-size_t MemTable::ApproximateMemoryUsage() { return arena_.MemoryUsage(); }
+size_t MemTable::ApproximateMemoryUsage() {
+  return arena_impl_.ApproximateMemoryUsage();
+}

 int MemTable::KeyComparator::operator()(const char* aptr, const char* bptr)
    const {
@@ -55,24 +65,27 @@ static const char* EncodeKey(std::string* scratch, const Slice& target) {

 class MemTableIterator: public Iterator {
 public:
-  explicit MemTableIterator(MemTable::Table* table) : iter_(table) { }
+  explicit MemTableIterator(MemTableRep* table)
+    : iter_(table->GetIterator()) { }

-  virtual bool Valid() const { return iter_.Valid(); }
-  virtual void Seek(const Slice& k) { iter_.Seek(EncodeKey(&tmp_, k)); }
-  virtual void SeekToFirst() { iter_.SeekToFirst(); }
-  virtual void SeekToLast() { iter_.SeekToLast(); }
-  virtual void Next() { iter_.Next(); }
-  virtual void Prev() { iter_.Prev(); }
-  virtual Slice key() const { return GetLengthPrefixedSlice(iter_.key()); }
+  virtual bool Valid() const { return iter_->Valid(); }
+  virtual void Seek(const Slice& k) { iter_->Seek(EncodeKey(&tmp_, k)); }
+  virtual void SeekToFirst() { iter_->SeekToFirst(); }
+  virtual void SeekToLast() { iter_->SeekToLast(); }
+  virtual void Next() { iter_->Next(); }
+  virtual void Prev() { iter_->Prev(); }
+  virtual Slice key() const {
+    return GetLengthPrefixedSlice(iter_->key());
+  }
  virtual Slice value() const {
-    Slice key_slice = GetLengthPrefixedSlice(iter_.key());
+    Slice key_slice = GetLengthPrefixedSlice(iter_->key());
    return GetLengthPrefixedSlice(key_slice.data() + key_slice.size());
  }

  virtual Status status() const { return Status::OK(); }

 private:
-  MemTable::Table::Iterator iter_;
+  std::shared_ptr<MemTableRep::Iterator> iter_;
  std::string tmp_;       // For passing to EncodeKey

  // No copying allowed
@@ -81,7 +94,7 @@ class MemTableIterator: public Iterator {
 };

 Iterator* MemTable::NewIterator() {
-  return new MemTableIterator(&table_);
+  return new MemTableIterator(table_.get());
 }

 void MemTable::Add(SequenceNumber s, ValueType type,
@@ -98,7 +111,7 @@ void MemTable::Add(SequenceNumber s, ValueType type,
  const size_t encoded_len =
      VarintLength(internal_key_size) + internal_key_size +
      VarintLength(val_size) + val_size;
-  char* buf = arena_.Allocate(encoded_len);
+  char* buf = arena_impl_.Allocate(encoded_len);
  char* p = EncodeVarint32(buf, internal_key_size);
  memcpy(p, key.data(), key_size);
  p += key_size;
@@ -107,7 +120,7 @@ void MemTable::Add(SequenceNumber s, ValueType type,
  p = EncodeVarint32(p, val_size);
  memcpy(p, value.data(), val_size);
  assert((p + val_size) - buf == (unsigned)encoded_len);
-  table_.Insert(buf);
+  table_->Insert(buf);

  // The first sequence number inserted into the memtable
  assert(first_seqno_ == 0 || s > first_seqno_);
@@ -116,11 +129,21 @@ void MemTable::Add(SequenceNumber s, ValueType type,
  }
 }

-bool MemTable::Get(const LookupKey& key, std::string* value, Status* s) {
+bool MemTable::Get(const LookupKey& key, std::string* value, Status* s,
+                   std::deque<std::string>* operands, const Options& options) {
  Slice memkey = key.memtable_key();
-  Table::Iterator iter(&table_);
-  iter.Seek(memkey.data());
-  if (iter.Valid()) {
+  std::shared_ptr<MemTableRep::Iterator> iter(table_.get()->GetIterator());
+  iter->Seek(memkey.data());
+
+  // It is the caller's responsibility to allocate/delete operands list
+  assert(operands != nullptr);
+
+  bool merge_in_progress = s->IsMergeInProgress();
+  auto merge_operator = options.merge_operator.get();
+  auto logger = options.info_log;
+  std::string merge_result;
+
+  for (; iter->Valid(); iter->Next()) {
    // entry format is:
    //    klength  varint32
    //    userkey  char[klength-8]
@@ -130,7 +153,7 @@ bool MemTable::Get(const LookupKey& key, std::string* value, Status* s) {
    // Check that it belongs to same user key.  We do not check the
    // sequence number since the Seek() call above should have skipped
    // all entries with overly large sequence numbers.
-    const char* entry = iter.key();
+    const char* entry = iter->key();
    uint32_t key_length;
    const char* key_ptr = GetVarint32Ptr(entry, entry+5, &key_length);
    if (comparator_.comparator.user_comparator()->Compare(
@@ -141,15 +164,68 @@ bool MemTable::Get(const LookupKey& key, std::string* value, Status* s) {
      switch (static_cast<ValueType>(tag & 0xff)) {
        case kTypeValue: {
          Slice v = GetLengthPrefixedSlice(key_ptr + key_length);
-          value->assign(v.data(), v.size());
+          *s = Status::OK();
+          if (merge_in_progress) {
+            assert(merge_operator);
+            if (!merge_operator->FullMerge(key.user_key(), &v, *operands,
+                                           value, logger.get())) {
+              RecordTick(options.statistics, NUMBER_MERGE_FAILURES);
+              *s = Status::Corruption("Error: Could not perform merge.");
+            }
+          } else {
+            value->assign(v.data(), v.size());
+          }
          return true;
        }
-        case kTypeDeletion:
-          *s = Status::NotFound(Slice());
+        case kTypeDeletion: {
+          if (merge_in_progress) {
+            assert(merge_operator);
+            *s = Status::OK();
+            if (!merge_operator->FullMerge(key.user_key(), nullptr, *operands,
+                                           value, logger.get())) {
+              RecordTick(options.statistics, NUMBER_MERGE_FAILURES);
+              *s = Status::Corruption("Error: Could not perform merge.");
+            }
+          } else {
+            *s = Status::NotFound(Slice());
+          }
          return true;
+        }
+        case kTypeMerge: {
+          Slice v = GetLengthPrefixedSlice(key_ptr + key_length);
+          merge_in_progress = true;
+          operands->push_front(v.ToString());
+          while(operands->size() >= 2) {
+            // Attempt to associative merge. (Returns true if successful)
+            if (merge_operator->PartialMerge(key.user_key(),
+                                             Slice((*operands)[0]),
+                                             Slice((*operands)[1]),
+                                             &merge_result,
+                                             logger.get())) {
+              operands->pop_front();
+              swap(operands->front(), merge_result);
+            } else {
+              // Stack them because user can't associative merge
+              break;
+            }
+          }
+          break;
+        }
+        case kTypeLogData:
+          assert(false);
+          break;
      }
+    } else {
+      // exit loop if user key does not match
+      break;
    }
  }
+
+  // No change to value, since we have not yet found a Put/Delete
+
+  if (merge_in_progress) {
+    *s = Status::MergeInProgress("");
+  }
  return false;
 }

@@ -6,24 +6,35 @@
 #define STORAGE_LEVELDB_DB_MEMTABLE_H_

 #include <string>
-#include "leveldb/db.h"
+#include <memory>
+#include <deque>
 #include "db/dbformat.h"
 #include "db/skiplist.h"
 #include "db/version_set.h"
-#include "util/arena.h"
+#include "leveldb/db.h"
+#include "leveldb/memtablerep.h"
+#include "util/arena_impl.h"

 namespace leveldb {

-class InternalKeyComparator;
 class Mutex;
 class MemTableIterator;

 class MemTable {
 public:
+  struct KeyComparator : public MemTableRep::KeyComparator {
+    const InternalKeyComparator comparator;
+    explicit KeyComparator(const InternalKeyComparator& c) : comparator(c) { }
+    virtual int operator()(const char* a, const char* b) const;
+  };
+
  // MemTables are reference counted.  The initial reference count
  // is zero and the caller must call Ref() at least once.
-  explicit MemTable(const InternalKeyComparator& comparator,
-                    int numlevel = 7);
+  explicit MemTable(
+    const InternalKeyComparator& comparator,
+    std::shared_ptr<MemTableRepFactory> table_factory,
+    int numlevel = 7,
+    const Options& options = Options());

  // Increase reference count.
  void Ref() { ++refs_; }
@@ -62,8 +73,13 @@ class MemTable {
  // If memtable contains a value for key, store it in *value and return true.
  // If memtable contains a deletion for key, store a NotFound() error
  // in *status and return true.
+  // If memtable contains Merge operation as the most recent entry for a key,
+  //   and the merge process does not stop (not reaching a value or delete),
+  //   prepend the current merge operand to *operands.
+  //   store MergeInProgress in s, and return false.
  // Else, return false.
-  bool Get(const LookupKey& key, std::string* value, Status* s);
+  bool Get(const LookupKey& key, std::string* value, Status* s,
+           std::deque<std::string>* operands, const Options& options);

  // Returns the edits area that is needed for flushing the memtable
  VersionEdit* GetEdits() { return &edit_; }
@@ -72,24 +88,24 @@ class MemTable {
  // into the memtable
  SequenceNumber GetFirstSequenceNumber() { return first_seqno_; }

+  // Returns the logfile number that can be safely deleted when this
+  // memstore is flushed to storage
+  uint64_t GetLogNumber() { return mem_logfile_number_; }
+
+  // Sets the logfile number that can be safely deleted when this
+  // memstore is flushed to storage
+  void SetLogNumber(uint64_t num) { mem_logfile_number_ = num; }
+
 private:
  ~MemTable();  // Private since only Unref() should be used to delete it
-
-  struct KeyComparator {
-    const InternalKeyComparator comparator;
-    explicit KeyComparator(const InternalKeyComparator& c) : comparator(c) { }
-    int operator()(const char* a, const char* b) const;
-  };
  friend class MemTableIterator;
  friend class MemTableBackwardIterator;
  friend class MemTableList;

-  typedef SkipList<const char*, KeyComparator> Table;
-
  KeyComparator comparator_;
  int refs_;
-  Arena arena_;
-  Table table_;
+  ArenaImpl arena_impl_;
+  shared_ptr<MemTableRep> table_;

  // These are used to manage memtable flushes to storage
  bool flush_in_progress_; // started the flush
@@ -103,6 +119,9 @@ class MemTable {
  // The sequence number of the kv that was inserted first
  SequenceNumber first_seqno_;

+  // The log files earlier than this number can be deleted.
+  uint64_t mem_logfile_number_;
+
  // No copying allowed
  MemTable(const MemTable&);
  void operator=(const MemTable&);
@@ -21,17 +21,15 @@ using std::list;

 // Increase reference count on all underling memtables
 void MemTableList::RefAll() {
-  for (list<MemTable*>::iterator it = memlist_.begin();
-       it != memlist_.end() ; ++it) {
-    (*it)->Ref();
+  for (auto &memtable : memlist_) {
+    memtable->Ref();
  }
 }

 // Drop reference count on all underling memtables
 void MemTableList::UnrefAll() {
-  for (list<MemTable*>::iterator it = memlist_.begin();
-       it != memlist_.end() ; ++it) {
-    (*it)->Unref();
+  for (auto &memtable : memlist_) {
+    memtable->Unref();
  }
 }

@@ -43,19 +41,17 @@ int MemTableList::size() {

 // Returns true if there is at least one memtable on which flush has
 // not yet started.
-bool MemTableList::IsFlushPending() {
-  if (num_flush_not_started_ > 0) {
+bool MemTableList::IsFlushPending(int min_write_buffer_number_to_merge) {
+  if (num_flush_not_started_ >= min_write_buffer_number_to_merge) {
    assert(imm_flush_needed.NoBarrier_Load() != nullptr);
    return true;
  }
  return false;
 }

-// Returns the earliest memtable that needs to be flushed.
-// Returns null, if no such memtable exist.
-MemTable* MemTableList::PickMemtableToFlush() {
-  for (list<MemTable*>::reverse_iterator it = memlist_.rbegin();
-       it != memlist_.rend(); it++) {
+// Returns the memtables that need to be flushed.
+void MemTableList::PickMemtablesToFlush(std::vector<MemTable*>* ret) {
+  for (auto it = memlist_.rbegin(); it != memlist_.rend(); it++) {
    MemTable* m = *it;
    if (!m->flush_in_progress_) {
      assert(!m->flush_completed_);
@@ -64,37 +60,48 @@ MemTable* MemTableList::PickMemtableToFlush() {
        imm_flush_needed.Release_Store(nullptr);
      }
      m->flush_in_progress_ = true; // flushing will start very soon
-      return m;
+      ret->push_back(m);
    }
  }
-  return nullptr;
 }

 // Record a successful flush in the manifest file
-Status MemTableList::InstallMemtableFlushResults(MemTable* m,
+Status MemTableList::InstallMemtableFlushResults(
+                      const std::vector<MemTable*> &mems,
                      VersionSet* vset, Status flushStatus,
                      port::Mutex* mu, Logger* info_log,
                      uint64_t file_number,
                      std::set<uint64_t>& pending_outputs) {
  mu->AssertHeld();
-  assert(m->flush_in_progress_);
-  assert(m->file_number_ == 0);

  // If the flush was not successful, then just reset state.
  // Maybe a suceeding attempt to flush will be successful.
  if (!flushStatus.ok()) {
-    m->flush_in_progress_ = false;
-    m->flush_completed_ = false;
-    m->edit_.Clear();
-    num_flush_not_started_++;
-    imm_flush_needed.Release_Store((void *)1);
-    pending_outputs.erase(file_number);
+    for (MemTable* m : mems) {
+      assert(m->flush_in_progress_);
+      assert(m->file_number_ == 0);
+
+      m->flush_in_progress_ = false;
+      m->flush_completed_ = false;
+      m->edit_.Clear();
+      num_flush_not_started_++;
+      imm_flush_needed.Release_Store((void *)1);
+      pending_outputs.erase(file_number);
+    }
    return flushStatus;
  }

  // flush was sucessful
-  m->flush_completed_ = true;
-  m->file_number_ = file_number;
+  bool first = true;
+  for (MemTable* m : mems) {
+
+    // All the edits are associated with the first memtable of this batch.
+    assert(first || m->GetEdits()->NumEntries() == 0);
+    first = false;
+
+    m->flush_completed_ = true;
+    m->file_number_ = file_number;
+  }

  // if some other thread is already commiting, then return
  Status s;
@@ -106,12 +113,15 @@ Status MemTableList::InstallMemtableFlushResults(MemTable* m,
  commit_in_progress_ = true;

  // scan all memtables from the earliest, and commit those
-  // (in that order) that have finished flushing.
-  while (!memlist_.empty()) {
-    m = memlist_.back(); // get the last element
+  // (in that order) that have finished flushing. Memetables
+  // are always committed in the order that they were created.
+  while (!memlist_.empty() && s.ok()) {
+    MemTable* m = memlist_.back(); // get the last element
    if (!m->flush_completed_) {
      break;
    }
+    first = true;
+
    Log(info_log,
        "Level-0 commit table #%llu: started",
        (unsigned long long)m->file_number_);
@@ -119,33 +129,39 @@ Status MemTableList::InstallMemtableFlushResults(MemTable* m,
    // this can release and reacquire the mutex.
    s = vset->LogAndApply(&m->edit_, mu);

-    if (s.ok()) { // commit new state
-      Log(info_log, "Level-0 commit table #%llu: done",
-                     (unsigned long long)m->file_number_);
-      memlist_.remove(m);
-      assert(m->file_number_ > 0);
+    // All the later memtables that have the same filenum
+    // are part of the same batch. They can be committed now.
+    do {
+      if (s.ok()) { // commit new state
+        Log(info_log, "Level-0 commit table #%llu: done %s",
+                       (unsigned long long)m->file_number_,
+                       first ? "": "bulk");
+        memlist_.remove(m);
+        assert(m->file_number_ > 0);

-      // pending_outputs can be cleared only after the newly created file
-      // has been written to a committed version so that other concurrently
-      // executing compaction threads do not mistakenly assume that this
-      // file is not live.
-      pending_outputs.erase(m->file_number_);
-      m->Unref();
-      size_--;
-    } else {
-      //commit failed. setup state so that we can flush again.
-      Log(info_log, "Level-0 commit table #%llu: failed",
-                     (unsigned long long)m->file_number_);
-      m->flush_completed_ = false;
-      m->flush_in_progress_ = false;
-      m->edit_.Clear();
-      num_flush_not_started_++;
-      pending_outputs.erase(m->file_number_);
-      m->file_number_ = 0;
-      imm_flush_needed.Release_Store((void *)1);
-      s = Status::IOError("Unable to commit flushed memtable");
-      break;
-    }
+        // pending_outputs can be cleared only after the newly created file
+        // has been written to a committed version so that other concurrently
+        // executing compaction threads do not mistakenly assume that this
+        // file is not live.
+        pending_outputs.erase(m->file_number_);
+        m->Unref();
+        size_--;
+      } else {
+        //commit failed. setup state so that we can flush again.
+        Log(info_log, "Level-0 commit table #%llu: failed",
+                       (unsigned long long)m->file_number_);
+        m->flush_completed_ = false;
+        m->flush_in_progress_ = false;
+        m->edit_.Clear();
+        num_flush_not_started_++;
+        pending_outputs.erase(m->file_number_);
+        m->file_number_ = 0;
+        imm_flush_needed.Release_Store((void *)1);
+        s = Status::IOError("Unable to commit flushed memtable");
+      }
+      first = false;
+    } while (!memlist_.empty() && (m = memlist_.back()) &&
+             m->file_number_ == file_number);
  }
  commit_in_progress_ = false;
  return s;
@@ -165,19 +181,20 @@ void MemTableList::Add(MemTable* m) {
 // Returns an estimate of the number of bytes of data in use.
 size_t MemTableList::ApproximateMemoryUsage() {
  size_t size = 0;
-  for (list<MemTable*>::iterator it = memlist_.begin();
-       it != memlist_.end(); ++it) {
-    size += (*it)->ApproximateMemoryUsage();
+  for (auto &memtable : memlist_) {
+    size += memtable->ApproximateMemoryUsage();
  }
  return size;
 }

 // Search all the memtables starting from the most recent one.
 // Return the most recent value found, if any.
-bool MemTableList::Get(const LookupKey& key, std::string* value, Status* s) {
-  for (list<MemTable*>::iterator it = memlist_.begin();
-       it != memlist_.end(); ++it) {
-    if ((*it)->Get(key, value, s)) {
+// Operands stores the list of merge operations to apply, so far.
+bool MemTableList::Get(const LookupKey& key, std::string* value, Status* s,
+                       std::deque<std::string>* operands,
+                       const Options& options) {
+  for (auto &memtable : memlist_) {
+    if (memtable->Get(key, value, s, operands, options)) {
      return true;
    }
  }
@@ -185,9 +202,8 @@ bool MemTableList::Get(const LookupKey& key, std::string* value, Status* s) {
 }

 void MemTableList::GetMemTables(std::vector<MemTable*>* output) {
-  for (list<MemTable*>::iterator it = memlist_.begin();
-       it != memlist_.end(); ++it) {
-    output->push_back(*it);
+  for (auto &memtable : memlist_) {
+    output->push_back(memtable);
  }
 }

@@ -5,10 +5,10 @@

 #include <string>
 #include <list>
+#include <deque>
 #include "leveldb/db.h"
 #include "db/dbformat.h"
 #include "db/skiplist.h"
-#include "util/arena.h"
 #include "memtable.h"

 namespace leveldb {
@@ -18,7 +18,7 @@ class Mutex;
 class MemTableListIterator;

 //
-// This class stores refeernces to all the immutable memtables.
+// This class stores references to all the immutable memtables.
 // The memtables are flushed to L0 as soon as possible and in
 // any order. If there are more than one immutable memtable, their
 // flushes can occur concurrently.  However, they are 'committed'
@@ -49,14 +49,13 @@ class MemTableList {

  // Returns true if there is at least one memtable on which flush has
  // not yet started.
-  bool IsFlushPending();
+  bool IsFlushPending(int min_write_buffer_number_to_merge);

-  // Returns the earliest memtable that needs to be flushed.
-  // Returns null, if no such memtable exist.
-  MemTable* PickMemtableToFlush();
+  // Returns the earliest memtables that needs to be flushed.
+  void PickMemtablesToFlush(std::vector<MemTable*>* mems);

  // Commit a successful flush in the manifest file
-  Status InstallMemtableFlushResults(MemTable* m,
+  Status InstallMemtableFlushResults(const std::vector<MemTable*> &m,
                      VersionSet* vset, Status flushStatus,
                      port::Mutex* mu, Logger* info_log,
                      uint64_t file_number,
@@ -71,7 +70,8 @@ class MemTableList {

  // Search all the memtables starting from the most recent one.
  // Return the most recent value found, if any.
-  bool Get(const LookupKey& key, std::string* value, Status* s);
+  bool Get(const LookupKey& key, std::string* value, Status* s,
+           std::deque<std::string>* operands, const Options& options);

  // Returns the list of underlying memtables.
  void GetMemTables(std::vector<MemTable*>* list);
@@ -0,0 +1,192 @@
+#include "merge_helper.h"
+#include "db/dbformat.h"
+#include "leveldb/comparator.h"
+#include "leveldb/db.h"
+#include "leveldb/merge_operator.h"
+#include <string>
+#include <stdio.h>
+
+namespace leveldb {
+
+// PRE:  iter points to the first merge type entry
+// POST: iter points to the first entry beyond the merge process (or the end)
+//       keys_, operands_ are updated to reflect the merge result.
+//       keys_ stores the list of keys encountered while merging.
+//       operands_ stores the list of merge operands encountered while merging.
+//       keys_[i] corresponds to operands_[i] for each i.
+void MergeHelper::MergeUntil(Iterator* iter, SequenceNumber stop_before,
+                             bool at_bottom, shared_ptr<Statistics> stats) {
+  // Get a copy of the internal key, before it's invalidated by iter->Next()
+  // Also maintain the list of merge operands seen.
+  keys_.clear();
+  operands_.clear();
+  keys_.push_front(iter->key().ToString());
+  operands_.push_front(iter->value().ToString());
+
+  success_ = false;   // Will become true if we hit Put/Delete or bottom
+
+  // We need to parse the internal key again as the parsed key is
+  // backed by the internal key!
+  // Assume no internal key corruption as it has been successfully parsed
+  // by the caller.
+  // Invariant: keys_.back() will not change. Hence, orig_ikey is always valid.
+  ParsedInternalKey orig_ikey;
+  ParseInternalKey(keys_.back(), &orig_ikey);
+
+  bool hit_the_next_user_key = false;
+  ParsedInternalKey ikey;
+  std::string merge_result;  // Temporary value for merge results
+  for (iter->Next(); iter->Valid(); iter->Next()) {
+    assert(operands_.size() >= 1);        // Should be invariants!
+    assert(keys_.size() == operands_.size());
+
+    if (!ParseInternalKey(iter->key(), &ikey)) {
+      // stop at corrupted key
+      if (assert_valid_internal_key_) {
+        assert(!"corrupted internal key is not expected");
+      }
+      break;
+    }
+
+    if (user_comparator_->Compare(ikey.user_key, orig_ikey.user_key) != 0) {
+      // hit a different user key, stop right here
+      hit_the_next_user_key = true;
+      break;
+    }
+
+    if (stop_before && ikey.sequence <= stop_before) {
+      // hit an entry that's visible by the previous snapshot, can't touch that
+      break;
+    }
+
+    // At this point we are guaranteed that we need to process this key.
+
+    if (kTypeDeletion == ikey.type) {
+      // hit a delete
+      //   => merge nullptr with operands_
+      //   => store result in operands_.back() (and update keys_.back())
+      //   => change the entry type to kTypeValue for keys_.back()
+      // We are done! Return a success if the merge passes.
+      success_ = user_merge_operator_->FullMerge(ikey.user_key, nullptr,
+                                                 operands_, &merge_result,
+                                                 logger_);
+
+      // We store the result in keys_.back() and operands_.back()
+      // if nothing went wrong (i.e.: no operand corruption on disk)
+      if (success_) {
+        std::string& key = keys_.back();  // The original key encountered
+        orig_ikey.type = kTypeValue;
+        UpdateInternalKey(&key[0], key.size(),
+                          orig_ikey.sequence, orig_ikey.type);
+        swap(operands_.back(), merge_result);
+      } else {
+        RecordTick(stats, NUMBER_MERGE_FAILURES);
+      }
+
+      // move iter to the next entry (before doing anything else)
+      iter->Next();
+      return;
+    }
+
+    if (kTypeValue == ikey.type) {
+      // hit a put
+      //   => merge the put value with operands_
+      //   => store result in operands_.back() (and update keys_.back())
+      //   => change the entry type to kTypeValue for keys_.back()
+      // We are done! Success!
+      const Slice value = iter->value();
+      success_ = user_merge_operator_->FullMerge(ikey.user_key, &value,
+                                                 operands_, &merge_result,
+                                                 logger_);
+
+      // We store the result in keys_.back() and operands_.back()
+      // if nothing went wrong (i.e.: no operand corruption on disk)
+      if (success_) {
+        std::string& key = keys_.back();  // The original key encountered
+        orig_ikey.type = kTypeValue;
+        UpdateInternalKey(&key[0], key.size(),
+                          orig_ikey.sequence, orig_ikey.type);
+        swap(operands_.back(), merge_result);
+      } else {
+        RecordTick(stats, NUMBER_MERGE_FAILURES);
+      }
+
+      // move iter to the next entry
+      iter->Next();
+      return;
+    }
+
+    if (kTypeMerge == ikey.type) {
+      // hit a merge
+      //   => merge the operand into the front of the operands_ list
+      //   => use the user's associative merge function to determine how.
+      //   => then continue because we haven't yet seen a Put/Delete.
+      assert(!operands_.empty()); // Should have at least one element in it
+
+      keys_.push_front(iter->key().ToString());
+      operands_.push_front(iter->value().ToString());
+      while (operands_.size() >= 2) {
+        // Returns false when the merge_operator can no longer process it
+        if (user_merge_operator_->PartialMerge(ikey.user_key,
+                                               Slice(operands_[0]),
+                                               Slice(operands_[1]),
+                                               &merge_result,
+                                               logger_)) {
+          // Merging of operands (associative merge) was successful.
+          // Replace these frontmost two operands with the merge result
+          keys_.pop_front();
+          operands_.pop_front();
+          swap(operands_.front(), merge_result);
+        } else {
+          // Merging of operands (associative merge) returned false.
+          // The user merge_operator does not know how to merge these operands.
+          // So we just stack them up until we find a Put/Delete or end of key.
+          break;
+        }
+      }
+      continue;
+    }
+  }
+
+  // We are sure we have seen this key's entire history if we are at the
+  // last level and exhausted all internal keys of this user key.
+  // NOTE: !iter->Valid() does not necessarily mean we hit the
+  // beginning of a user key, as versions of a user key might be
+  // split into multiple files (even files on the same level)
+  // and some files might not be included in the compaction/merge.
+  //
+  // There are also cases where we have seen the root of history of this
+  // key without being sure of it. Then, we simply miss the opportunity
+  // to combine the keys. Since VersionSet::SetupOtherInputs() always makes
+  // sure that all merge-operands on the same level get compacted together,
+  // this will simply lead to these merge operands moving to the next level.
+  //
+  // So, we only perform the following logic (to merge all operands together
+  // without a Put/Delete) if we are certain that we have seen the end of key.
+  bool surely_seen_the_beginning = hit_the_next_user_key && at_bottom;
+  if (surely_seen_the_beginning) {
+    // do a final merge with nullptr as the existing value and say
+    // bye to the merge type (it's now converted to a Put)
+    assert(kTypeMerge == orig_ikey.type);
+    assert(operands_.size() >= 1);
+    assert(operands_.size() == keys_.size());
+    success_ = user_merge_operator_->FullMerge(ikey.user_key, nullptr,
+                                               operands_, &merge_result,
+                                               logger_);
+
+    if (success_) {
+      std::string& key = keys_.back();  // The original key encountered
+      orig_ikey.type = kTypeValue;
+      UpdateInternalKey(&key[0], key.size(),
+                        orig_ikey.sequence, orig_ikey.type);
+
+      // The final value() is always stored in operands_.back()
+      swap(operands_.back(),merge_result);
+    } else {
+      RecordTick(stats, NUMBER_MERGE_FAILURES);
+      // Do nothing if not success_. Leave keys() and operands() as they are.
+    }
+  }
+}
+
+} // namespace leveldb
@@ -0,0 +1,98 @@
+#ifndef MERGE_HELPER_H
+#define MERGE_HELPER_H
+
+#include "db/dbformat.h"
+#include "leveldb/slice.h"
+#include "leveldb/statistics.h"
+#include <string>
+#include <deque>
+
+namespace leveldb {
+
+class Comparator;
+class Iterator;
+class Logger;
+class MergeOperator;
+
+class MergeHelper {
+ public:
+  MergeHelper(const Comparator* user_comparator,
+              const MergeOperator* user_merge_operator,
+              Logger* logger,
+              bool assert_valid_internal_key)
+      : user_comparator_(user_comparator),
+        user_merge_operator_(user_merge_operator),
+        logger_(logger),
+        assert_valid_internal_key_(assert_valid_internal_key),
+        keys_(),
+        operands_(),
+        success_(false) {}
+
+  // Merge entries until we hit
+  //     - a corrupted key
+  //     - a Put/Delete,
+  //     - a different user key,
+  //     - a specific sequence number (snapshot boundary),
+  //  or - the end of iteration
+  // iter: (IN)  points to the first merge type entry
+  //       (OUT) points to the first entry not included in the merge process
+  // stop_before: (IN) a sequence number that merge should not cross.
+  //                   0 means no restriction
+  // at_bottom:   (IN) true if the iterator covers the bottem level, which means
+  //                   we could reach the start of the history of this user key.
+  void MergeUntil(Iterator* iter, SequenceNumber stop_before = 0,
+                  bool at_bottom = false, shared_ptr<Statistics> stats=nullptr);
+
+  // Query the merge result
+  // These are valid until the next MergeUntil call
+  // If the merging was successful:
+  //   - IsSuccess() will be true
+  //   - key() will have the latest sequence number of the merges.
+  //           The type will be Put or Merge. See IMPORTANT 1 note, below.
+  //   - value() will be the result of merging all the operands together
+  //   - The user should ignore keys() and values().
+  //
+  //   IMPORTANT 1: the key type could change after the MergeUntil call.
+  //        Put/Delete + Merge + ... + Merge => Put
+  //        Merge + ... + Merge => Merge
+  //
+  // If the merge operator is not associative, and if a Put/Delete is not found
+  // then the merging will be unsuccessful. In this case:
+  //   - IsSuccess() will be false
+  //   - keys() contains the list of internal keys seen in order of iteration.
+  //   - values() contains the list of values (merges) seen in the same order.
+  //              values() is parallel to keys() so that the first entry in
+  //              keys() is the key associated with the first entry in values()
+  //              and so on. These lists will be the same length.
+  //              All of these pairs will be merges over the same user key.
+  //              See IMPORTANT 2 note below.
+  //   - The user should ignore key() and value().
+  //
+  //   IMPORTANT 2: The entries were traversed in order from BACK to FRONT.
+  //                So keys().back() was the first key seen by iterator.
+  // TODO: Re-style this comment to be like the first one
+  bool IsSuccess() { return success_; }
+  Slice key() { assert(success_); return Slice(keys_.back()); }
+  Slice value() { assert(success_); return Slice(operands_.back()); }
+  const std::deque<std::string>& keys() { assert(!success_); return keys_; }
+  const std::deque<std::string>& values() {
+    assert(!success_); return operands_;
+  }
+
+ private:
+  const Comparator* user_comparator_;
+  const MergeOperator* user_merge_operator_;
+  Logger* logger_;
+  Iterator* iter_; // in: the internal iterator, positioned at the first merge entry
+  bool assert_valid_internal_key_; // enforce no internal key corruption?
+
+  // the scratch area that holds the result of MergeUntil
+  // valid up to the next MergeUntil call
+  std::deque<std::string> keys_;    // Keeps track of the sequence of keys seen
+  std::deque<std::string> operands_;  // Parallel with keys_; stores the values
+  bool success_;
+};
+
+} // namespace leveldb
+
+#endif
@@ -0,0 +1,51 @@
+/**
+ * Back-end implementation details specific to the Merge Operator.
+ *
+ * @author Deon Nicholas (dnicholas@fb.com)
+ * Copyright 2013 Facebook
+ */
+
+#include "leveldb/merge_operator.h"
+
+namespace leveldb {
+
+// Given a "real" merge from the library, call the user's
+// associative merge function one-by-one on each of the operands.
+// NOTE: It is assumed that the client's merge-operator will handle any errors.
+bool AssociativeMergeOperator::FullMerge(
+    const Slice& key,
+    const Slice* existing_value,
+    const std::deque<std::string>& operand_list,
+    std::string* new_value,
+    Logger* logger) const {
+
+  // Simply loop through the operands
+  Slice temp_existing;
+  std::string temp_value;
+  for (const auto& operand : operand_list) {
+    Slice value(operand);
+    if (!Merge(key, existing_value, value, &temp_value, logger)) {
+      return false;
+    }
+    swap(temp_value, *new_value);
+    temp_existing = Slice(*new_value);
+    existing_value = &temp_existing;
+  }
+
+  // The result will be in *new_value. All merges succeeded.
+  return true;
+}
+
+// Call the user defined simple merge on the operands;
+// NOTE: It is assumed that the client's merge-operator will handle any errors.
+bool AssociativeMergeOperator::PartialMerge(
+    const Slice& key,
+    const Slice& left_operand,
+    const Slice& right_operand,
+    std::string* new_value,
+    Logger* logger) const {
+
+  return Merge(key, &left_operand, right_operand, new_value, logger);
+}
+
+} // namespace leveldb
@@ -0,0 +1,270 @@
+#include <assert.h>
+#include <memory>
+#include <iostream>
+
+#include "leveldb/cache.h"
+#include "leveldb/comparator.h"
+#include "leveldb/db.h"
+#include "leveldb/env.h"
+#include "leveldb/merge_operator.h"
+#include "db/dbformat.h"
+#include "db/db_impl.h"
+#include "utilities/merge_operators.h"
+#include "util/testharness.h"
+#include "utilities/utility_db.h"
+
+using namespace std;
+using namespace leveldb;
+
+
+std::shared_ptr<DB> OpenDb(const string& dbname, const bool ttl = false) {
+  DB* db;
+  StackableDB* sdb;
+  Options options;
+  options.create_if_missing = true;
+  options.merge_operator = MergeOperators::CreateUInt64AddOperator();
+  Status s;
+  DestroyDB(dbname, Options());
+  if (ttl) {
+    cout << "Opening database with TTL\n";
+    s = UtilityDB::OpenTtlDB(options, dbname, &sdb);
+    db = sdb;
+  } else {
+    s = DB::Open(options, dbname, &db);
+  }
+  if (!s.ok()) {
+    cerr << s.ToString() << endl;
+    assert(false);
+  }
+  return std::shared_ptr<DB>(db);
+}
+
+// Imagine we are maintaining a set of uint64 counters.
+// Each counter has a distinct name. And we would like
+// to support four high level operations:
+// set, add, get and remove
+// This is a quick implementation without a Merge operation.
+class Counters {
+
+ protected:
+  std::shared_ptr<DB> db_;
+
+  WriteOptions put_option_;
+  ReadOptions get_option_;
+  WriteOptions delete_option_;
+
+  uint64_t default_;
+
+ public:
+  explicit Counters(std::shared_ptr<DB> db, uint64_t defaultCount = 0)
+      : db_(db),
+        put_option_(),
+        get_option_(),
+        delete_option_(),
+        default_(defaultCount) {
+    assert(db_);
+  }
+
+  virtual ~Counters() {}
+
+  // public interface of Counters.
+  // All four functions return false
+  // if the underlying level db operation failed.
+
+  // mapped to a levedb Put
+  bool set(const string& key, uint64_t value) {
+    // just treat the internal rep of int64 as the string
+    Slice slice((char *)&value, sizeof(value));
+    auto s = db_->Put(put_option_, key, slice);
+
+    if (s.ok()) {
+      return true;
+    } else {
+      cerr << s.ToString() << endl;
+      return false;
+    }
+  }
+
+  // mapped to a leveldb Delete
+  bool remove(const string& key) {
+    auto s = db_->Delete(delete_option_, key);
+
+    if (s.ok()) {
+      return true;
+    } else {
+      cerr << s.ToString() << std::endl;
+      return false;
+    }
+  }
+
+  // mapped to a leveldb Get
+  bool get(const string& key, uint64_t *value) {
+    string str;
+    auto s = db_->Get(get_option_, key, &str);
+
+    if (s.IsNotFound()) {
+      // return default value if not found;
+      *value = default_;
+      return true;
+    } else if (s.ok()) {
+      // deserialization
+      if (str.size() != sizeof(uint64_t)) {
+        cerr << "value corruption\n";
+        return false;
+      }
+      *value = DecodeFixed64(&str[0]);
+      return true;
+    } else {
+      cerr << s.ToString() << std::endl;
+      return false;
+    }
+  }
+
+  // 'add' is implemented as get -> modify -> set
+  // An alternative is a single merge operation, see MergeBasedCounters
+  virtual bool add(const string& key, uint64_t value) {
+    uint64_t base = default_;
+    return get(key, &base) && set(key, base + value);
+  }
+
+
+  // convenience functions for testing
+  void assert_set(const string& key, uint64_t value) {
+    assert(set(key, value));
+  }
+
+  void assert_remove(const string& key) {
+    assert(remove(key));
+  }
+
+  uint64_t assert_get(const string& key) {
+    uint64_t value = default_;
+    assert(get(key, &value));
+    return value;
+  }
+
+  void assert_add(const string& key, uint64_t value) {
+    assert(add(key, value));
+  }
+};
+
+// Implement 'add' directly with the new Merge operation
+class MergeBasedCounters : public Counters {
+ private:
+  WriteOptions merge_option_; // for merge
+
+ public:
+  explicit MergeBasedCounters(std::shared_ptr<DB> db, uint64_t defaultCount = 0)
+      : Counters(db, defaultCount),
+        merge_option_() {
+  }
+
+  // mapped to a leveldb Merge operation
+  virtual bool add(const string& key, uint64_t value) override {
+    char encoded[sizeof(uint64_t)];
+    EncodeFixed64(encoded, value);
+    Slice slice(encoded, sizeof(uint64_t));
+    auto s = db_->Merge(merge_option_, key, slice);
+
+    if (s.ok()) {
+      return true;
+    } else {
+      cerr << s.ToString() << endl;
+      return false;
+    }
+  }
+};
+
+void dumpDb(DB* db) {
+  auto it = unique_ptr<Iterator>(db->NewIterator(ReadOptions()));
+  for (it->SeekToFirst(); it->Valid(); it->Next()) {
+    uint64_t value = DecodeFixed64(it->value().data());
+    cout << it->key().ToString() << ": "  << value << endl;
+  }
+  assert(it->status().ok());  // Check for any errors found during the scan
+}
+
+void testCounters(Counters& counters, DB* db, bool test_compaction) {
+
+  FlushOptions o;
+  o.wait = true;
+
+  counters.assert_set("a", 1);
+
+  if (test_compaction) db->Flush(o);
+
+  assert(counters.assert_get("a") == 1);
+
+  counters.assert_remove("b");
+
+  // defaut value is 0 if non-existent
+  assert(counters.assert_get("b") == 0);
+
+  counters.assert_add("a", 2);
+
+  if (test_compaction) db->Flush(o);
+
+  // 1+2 = 3
+  assert(counters.assert_get("a")== 3);
+
+  dumpDb(db);
+
+  std::cout << "1\n";
+
+  // 1+...+49 = ?
+  uint64_t sum = 0;
+  for (int i = 1; i < 50; i++) {
+    counters.assert_add("b", i);
+    sum += i;
+  }
+  assert(counters.assert_get("b") == sum);
+
+  std::cout << "2\n";
+  dumpDb(db);
+
+  std::cout << "3\n";
+
+  if (test_compaction) {
+    db->Flush(o);
+
+    cout << "Compaction started ...\n";
+    db->CompactRange(nullptr, nullptr);
+    cout << "Compaction ended\n";
+
+    dumpDb(db);
+
+    assert(counters.assert_get("a")== 3);
+    assert(counters.assert_get("b") == sum);
+  }
+}
+
+void runTest(int argc, const string& dbname, const bool use_ttl = false) {
+  auto db = OpenDb(dbname, use_ttl);
+
+  {
+    cout << "Test read-modify-write counters... \n";
+    Counters counters(db, 0);
+    testCounters(counters, db.get(), true);
+  }
+
+  bool compact = false;
+  if (argc > 1) {
+    compact = true;
+    cout << "Turn on Compaction\n";
+  }
+
+  {
+    cout << "Test merge-based counters... \n";
+    MergeBasedCounters counters(db, 0);
+    testCounters(counters, db.get(), compact);
+  }
+
+  DestroyDB(dbname, Options());
+}
+
+int main(int argc, char *argv[]) {
+  //TODO: Make this test like a general rocksdb unit-test
+  runTest(argc, test::TmpDir() + "/merge_testdb");
+  runTest(argc, test::TmpDir() + "/merge_testdbttl", true); // Run test on TTL database
+  return 0;
+}
@@ -0,0 +1,12 @@
+#include "include/leveldb/perf_context.h"
+
+
+namespace leveldb {
+
+void PerfContext::Reset() {
+  user_key_comparison_count = 0;
+}
+
+__thread PerfContext perf_context;
+
+}
@@ -0,0 +1,81 @@
+#include <iostream>
+
+#include "leveldb/db.h"
+#include "leveldb/perf_context.h"
+#include "util/testharness.h"
+
+
+namespace leveldb {
+
+// Path to the database on file system
+const std::string kDbName = test::TmpDir() + "/perf_context_test";
+
+std::shared_ptr<DB> OpenDb() {
+    DB* db;
+    Options options;
+    options.create_if_missing = true;
+    options.write_buffer_size = 1000000000;     // give it a big memtable
+    Status s = DB::Open(options, kDbName,  &db);
+    ASSERT_OK(s);
+    return std::shared_ptr<DB>(db);
+}
+
+class PerfContextTest { };
+
+int kTotalKeys = 100;
+
+TEST(PerfContextTest, KeyComparisonCount) {
+
+  DestroyDB(kDbName, Options());    // Start this test with a fresh DB
+
+  auto db = OpenDb();
+
+  WriteOptions write_options;
+  ReadOptions read_options;
+
+  uint64_t total_user_key_comparison_get = 0;
+  uint64_t total_user_key_comparison_put = 0;
+  uint64_t max_user_key_comparison_get = 0;
+
+  std::cout << "Inserting " << kTotalKeys << " key/value pairs\n...\n";
+
+  for (int i = 0; i < kTotalKeys; ++i) {
+    std::string key = "k" + std::to_string(i);
+    std::string value = "v" + std::to_string(i);
+
+    perf_context.Reset();
+    db->Put(write_options, key, value);
+    total_user_key_comparison_put += perf_context.user_key_comparison_count;
+
+    perf_context.Reset();
+    db->Get(read_options, key, &value);
+    total_user_key_comparison_get += perf_context.user_key_comparison_count;
+    max_user_key_comparison_get =
+      std::max(max_user_key_comparison_get,
+               perf_context.user_key_comparison_count);
+  }
+
+  std::cout << "total user key comparison get: "
+            << total_user_key_comparison_get << "\n"
+            << "total user key comparison put: "
+            << total_user_key_comparison_put << "\n"
+            << "max user key comparison get: "
+            << max_user_key_comparison_get << "\n"
+            << "avg user key comparison get:"
+            << total_user_key_comparison_get/kTotalKeys << "\n";
+
+}
+
+
+}
+
+
+int main(int argc, char** argv) {
+
+  if (argc > 1) {
+    leveldb::kTotalKeys = std::stoi(argv[1]);
+  }
+
+  leveldb::test::RunAllTests();
+  return 0;
+}
@@ -0,0 +1,76 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Wrap an underlying iterator, but exclude any results not starting
+// with a given prefix.  Seeking to keys not beginning with the prefix
+// is invalid, and SeekToLast is not implemented (that would be
+// non-trivial), but otherwise this iterator will behave just like the
+// underlying iterator would if there happened to be no non-matching
+// keys in the dataset.
+
+#ifndef STORAGE_LEVELDB_DB_PREFIX_FILTER_ITERATOR_H_
+#define STORAGE_LEVELDB_DB_PREFIX_FILTER_ITERATOR_H_
+
+#include "leveldb/iterator.h"
+
+namespace leveldb {
+
+class PrefixFilterIterator : public Iterator {
+ private:
+  Iterator* iter_;
+  const Slice &prefix_;
+  const SliceTransform *prefix_extractor_;
+  Status status_;
+
+ public:
+  PrefixFilterIterator(Iterator* iter,
+                       const Slice &prefix,
+                       const SliceTransform* prefix_extractor)
+                             : iter_(iter), prefix_(prefix),
+                               prefix_extractor_(prefix_extractor),
+                               status_(Status::OK()) {
+    if (prefix_extractor == nullptr) {
+      status_ = Status::InvalidArgument("A prefix filter may not be used "
+                                        "unless a function is also defined "
+                                        "for extracting prefixes");
+    } else if (!prefix_extractor_->InRange(prefix)) {
+      status_ = Status::InvalidArgument("Must provide a slice for prefix which"
+                                        "is a prefix for some key");
+    }
+  }
+  ~PrefixFilterIterator() {
+    delete iter_;
+  }
+  Slice key() const { return iter_->key(); }
+  Slice value() const { return iter_->value(); }
+  Status status() const {
+    if (!status_.ok()) {
+      return status_;
+    }
+    return iter_->status();
+  }
+  void Next() { iter_->Next(); }
+  void Prev() { iter_->Prev(); }
+  void Seek(const Slice& k) {
+    if (prefix_extractor_->Transform(k) == prefix_) {
+      iter_->Seek(k);
+    } else {
+      status_ = Status::InvalidArgument("Seek must begin with target prefix");
+    }
+  }
+  void SeekToFirst() {
+    Seek(prefix_);
+  }
+  void SeekToLast() {
+    status_ = Status::NotSupported("SeekToLast is incompatible with prefixes");
+  }
+  bool Valid() const {
+    return (status_.ok() && iter_->Valid() &&
+            prefix_extractor_->Transform(iter_->key()) == prefix_);
+  }
+};
+
+}  // namespace leveldb
+
+#endif
@@ -52,7 +52,7 @@ class Repairer {
        options_(SanitizeOptions(dbname, &icmp_, &ipolicy_, options)),
        next_file_number_(1) {
    // TableCache can be small since we expect each table to be opened once.
-    table_cache_ = new TableCache(dbname_, &options_, 10);
+    table_cache_ = new TableCache(dbname_, &options_, storage_options_, 10);
    edit_ = new VersionEdit(options.num_levels);
  }

@@ -88,6 +88,7 @@ class Repairer {
 private:
  struct TableInfo {
    FileMetaData meta;
+    SequenceNumber min_sequence;
    SequenceNumber max_sequence;
  };

@@ -105,6 +106,7 @@ class Repairer {
  std::vector<uint64_t> logs_;
  std::vector<TableInfo> tables_;
  uint64_t next_file_number_;
+  const EnvOptions storage_options_;

  Status FindFiles() {
    std::vector<std::string> filenames;
@@ -169,7 +171,7 @@ class Repairer {
    // Open the log file
    std::string logname = LogFileName(dbname_, log);
    unique_ptr<SequentialFile> lfile;
-    Status status = env_->NewSequentialFile(logname, &lfile);
+    Status status = env_->NewSequentialFile(logname, &lfile, storage_options_);
    if (!status.ok()) {
      return status;
    }
@@ -190,7 +192,8 @@ class Repairer {
    std::string scratch;
    Slice record;
    WriteBatch batch;
-    MemTable* mem = new MemTable(icmp_, options_.num_levels);
+    MemTable* mem = new MemTable(icmp_, options_.memtable_factory,
+      options_.num_levels);
    mem->Ref();
    int counter = 0;
    while (reader.ReadRecord(&record, &scratch)) {
@@ -216,7 +219,8 @@ class Repairer {
    FileMetaData meta;
    meta.number = next_file_number_++;
    Iterator* iter = mem->NewIterator();
-    status = BuildTable(dbname_, env_, options_, table_cache_, iter, &meta,
+    status = BuildTable(dbname_, env_, options_, storage_options_,
+                        table_cache_, iter, &meta,
                        icmp_.user_comparator(), 0, 0);
    delete iter;
    mem->Unref();
@@ -258,9 +262,10 @@ class Repairer {
    Status status = env_->GetFileSize(fname, &t->meta.file_size);
    if (status.ok()) {
      Iterator* iter = table_cache_->NewIterator(
-          ReadOptions(), t->meta.number, t->meta.file_size);
+          ReadOptions(), storage_options_, t->meta.number, t->meta.file_size);
      bool empty = true;
      ParsedInternalKey parsed;
+      t->min_sequence = 0;
      t->max_sequence = 0;
      for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
        Slice key = iter->key();
@@ -277,6 +282,9 @@ class Repairer {
          t->meta.smallest.DecodeFrom(key);
        }
        t->meta.largest.DecodeFrom(key);
+        if (parsed.sequence < t->min_sequence) {
+          t->min_sequence = parsed.sequence;
+        }
        if (parsed.sequence > t->max_sequence) {
          t->max_sequence = parsed.sequence;
        }
@@ -296,7 +304,7 @@ class Repairer {
  Status WriteDescriptor() {
    std::string tmp = TempFileName(dbname_, 1);
    unique_ptr<WritableFile> file;
-    Status status = env_->NewWritableFile(tmp, &file);
+    Status status = env_->NewWritableFile(tmp, &file, storage_options_);
    if (!status.ok()) {
      return status;
    }
@@ -317,7 +325,8 @@ class Repairer {
      // TODO(opt): separate out into multiple levels
      const TableInfo& t = tables_[i];
      edit_->AddFile(0, t.meta.number, t.meta.file_size,
-                    t.meta.smallest, t.meta.largest);
+                    t.meta.smallest, t.meta.largest,
+                    t.min_sequence, t.max_sequence);
    }

    //fprintf(stderr, "NewDescriptor:\n%s\n", edit_.DebugString().c_str());
@@ -31,13 +31,10 @@
 #include <assert.h>
 #include <stdlib.h>
 #include "port/port.h"
-#include "util/arena.h"
 #include "util/random.h"

 namespace leveldb {

-class Arena;
-
 template<typename Key, class Comparator>
 class SkipList {
 private:
@@ -5,7 +5,7 @@
 #include "db/skiplist.h"
 #include <set>
 #include "leveldb/env.h"
-#include "util/arena.h"
+#include "util/arena_impl.h"
 #include "util/hash.h"
 #include "util/random.h"
 #include "util/testharness.h"
@@ -29,9 +29,9 @@ struct TestComparator {
 class SkipTest { };

 TEST(SkipTest, Empty) {
-  Arena arena;
+  ArenaImpl arena_impl;
  TestComparator cmp;
-  SkipList<Key, TestComparator> list(cmp, &arena);
+  SkipList<Key, TestComparator> list(cmp, &arena_impl);
  ASSERT_TRUE(!list.Contains(10));

  SkipList<Key, TestComparator>::Iterator iter(&list);
@@ -49,9 +49,9 @@ TEST(SkipTest, InsertAndLookup) {
  const int R = 5000;
  Random rnd(1000);
  std::set<Key> keys;
-  Arena arena;
+  ArenaImpl arena_impl;
  TestComparator cmp;
-  SkipList<Key, TestComparator> list(cmp, &arena);
+  SkipList<Key, TestComparator> list(cmp, &arena_impl);
  for (int i = 0; i < N; i++) {
    Key key = rnd.Next() % R;
    if (keys.insert(key).second) {
@@ -204,14 +204,14 @@ class ConcurrentTest {
  // Current state of the test
  State current_;

-  Arena arena_;
+  ArenaImpl arena_impl_;

  // SkipList is not protected by mu_.  We just use a single writer
  // thread to modify it.
  SkipList<Key, TestComparator> list_;

 public:
-  ConcurrentTest() : list_(TestComparator(), &arena_) { }
+  ConcurrentTest() : list_(TestComparator(), &arena_impl_) { }

  // REQUIRES: External synchronization
  void WriteStep(Random* rnd) {
@@ -0,0 +1,102 @@
+#ifndef STORAGE_LEVELDB_DB_SKIPLISTREP_H_
+#define STORAGE_LEVELDB_DB_SKIPLISTREP_H_
+
+#include "leveldb/memtablerep.h"
+#include "db/memtable.h"
+#include "db/skiplist.h"
+
+namespace leveldb {
+
+class Arena;
+
+class SkipListRep : public MemTableRep {
+  SkipList<const char*, MemTableRep::KeyComparator&> skip_list_;
+public:
+  explicit SkipListRep(MemTableRep::KeyComparator& compare, Arena* arena)
+    : skip_list_(compare, arena) {
+}
+
+  // Insert key into the list.
+  // REQUIRES: nothing that compares equal to key is currently in the list.
+  virtual void Insert(const char* key) {
+    skip_list_.Insert(key);
+  }
+
+  // Returns true iff an entry that compares equal to key is in the list.
+  virtual bool Contains(const char* key) const {
+    return skip_list_.Contains(key);
+  }
+
+  virtual ~SkipListRep() { }
+
+  // Iteration over the contents of a skip list
+  class Iterator : public MemTableRep::Iterator {
+    SkipList<const char*, MemTableRep::KeyComparator&>::Iterator iter_;
+   public:
+    // Initialize an iterator over the specified list.
+    // The returned iterator is not valid.
+    explicit Iterator(
+      const SkipList<const char*, MemTableRep::KeyComparator&>* list
+    ) : iter_(list) { }
+
+    virtual ~Iterator() { }
+
+    // Returns true iff the iterator is positioned at a valid node.
+    virtual bool Valid() const {
+      return iter_.Valid();
+    }
+
+    // Returns the key at the current position.
+    // REQUIRES: Valid()
+    virtual const char* key() const {
+      return iter_.key();
+    }
+
+    // Advances to the next position.
+    // REQUIRES: Valid()
+    virtual void Next() {
+      iter_.Next();
+    }
+
+    // Advances to the previous position.
+    // REQUIRES: Valid()
+    virtual void Prev() {
+      iter_.Prev();
+    }
+
+    // Advance to the first entry with a key >= target
+    virtual void Seek(const char* target) {
+      iter_.Seek(target);
+    }
+
+    // Position at the first entry in list.
+    // Final state of iterator is Valid() iff list is not empty.
+    virtual void SeekToFirst() {
+      iter_.SeekToFirst();
+    }
+
+    // Position at the last entry in list.
+    // Final state of iterator is Valid() iff list is not empty.
+    virtual void SeekToLast() {
+      iter_.SeekToLast();
+    }
+  };
+
+  virtual std::shared_ptr<MemTableRep::Iterator> GetIterator() {
+    return std::shared_ptr<MemTableRep::Iterator>(
+      new SkipListRep::Iterator(&skip_list_)
+    );
+  }
+};
+
+class SkipListFactory : public MemTableRepFactory {
+public:
+  virtual std::shared_ptr<MemTableRep> CreateMemTableRep (
+    MemTableRep::KeyComparator& compare, Arena* arena) {
+      return std::shared_ptr<MemTableRep>(new SkipListRep(compare, arena));
+  }
+};
+
+}
+
+#endif // STORAGE_LEVELDB_DB_SKIPLISTREP_H_
@@ -59,12 +59,9 @@ class SnapshotList {

  // retrieve all snapshot numbers. They are sorted in ascending order.
  void getAll(std::vector<SequenceNumber>& ret) {
-    SnapshotImpl* s = &list_;
    if (empty()) return;
-    SequenceNumber prev __attribute__((unused)) = 0;
+    SnapshotImpl* s = &list_;
    while (s->next_ != &list_) {
-      assert(prev <= s->next_->number_);
-      assert(prev = s->next_->number_); // assignment
      ret.push_back(s->next_->number_);
      s = s ->next_;
    }
@@ -6,23 +6,16 @@

 #include "db/filename.h"

-#include "leveldb/env.h"
-#include "leveldb/table.h"
 #include "leveldb/statistics.h"
+#include "table/table.h"
 #include "util/coding.h"
+#include "util/stop_watch.h"

 namespace leveldb {

-struct TableAndFile {
-  unique_ptr<Table> table;
-};
-
-static class Statistics* dbstatistics;
-
 static void DeleteEntry(const Slice& key, void* value) {
-  TableAndFile* tf = reinterpret_cast<TableAndFile*>(value);
-  RecordTick(dbstatistics, NO_FILE_CLOSES);
-  delete tf;
+  Table* table = reinterpret_cast<Table*>(value);
+  delete table;
 }

 static void UnrefEntry(void* arg1, void* arg2) {
@@ -33,35 +26,44 @@ static void UnrefEntry(void* arg1, void* arg2) {

 TableCache::TableCache(const std::string& dbname,
                       const Options* options,
+                       const EnvOptions& storage_options,
                       int entries)
    : env_(options->env),
      dbname_(dbname),
      options_(options),
-      cache_(NewLRUCache(entries, options->table_cache_numshardbits)) {
-  dbstatistics = options->statistics;
-}
+      storage_options_(storage_options),
+      cache_(NewLRUCache(entries, options->table_cache_numshardbits)) {}

 TableCache::~TableCache() {
 }

-Status TableCache::FindTable(uint64_t file_number, uint64_t file_size,
-                             Cache::Handle** handle, bool* tableIO) {
+Status TableCache::FindTable(const EnvOptions& toptions,
+                             uint64_t file_number, uint64_t file_size,
+                             Cache::Handle** handle, bool* table_io,
+                             const bool no_io) {
  Status s;
  char buf[sizeof(file_number)];
  EncodeFixed64(buf, file_number);
  Slice key(buf, sizeof(buf));
  *handle = cache_->Lookup(key);
  if (*handle == nullptr) {
-    if (tableIO != nullptr) {
-      *tableIO = true;    // we had to do IO from storage
+    if (no_io) { // Dont do IO and return a not-found status
+      return Status::NotFound("Table not found in table_cache, no_io is set");
+    }
+    if (table_io != nullptr) {
+      *table_io = true;    // we had to do IO from storage
    }
    std::string fname = TableFileName(dbname_, file_number);
    unique_ptr<RandomAccessFile> file;
    unique_ptr<Table> table;
-    s = env_->NewRandomAccessFile(fname, &file);
+    s = env_->NewRandomAccessFile(fname, &file, toptions);
    RecordTick(options_->statistics, NO_FILE_OPENS);
    if (s.ok()) {
-      s = Table::Open(*options_, std::move(file), file_size, &table);
+      if (options_->advise_random_on_open) {
+        file->Hint(RandomAccessFile::RANDOM);
+      }
+      StopWatch sw(env_, options_->statistics, TABLE_OPEN_IO_MICROS);
+      s = Table::Open(*options_, toptions, std::move(file), file_size, &table);
    }

    if (!s.ok()) {
@@ -70,36 +72,41 @@ Status TableCache::FindTable(uint64_t file_number, uint64_t file_size,
      // We do not cache error results so that if the error is transient,
      // or somebody repairs the file, we recover automatically.
    } else {
-      TableAndFile* tf = new TableAndFile;
-      tf->table = std::move(table);
      assert(file.get() == nullptr);
-      *handle = cache_->Insert(key, tf, 1, &DeleteEntry);
+      *handle = cache_->Insert(key, table.release(), 1, &DeleteEntry);
    }
  }
  return s;
 }

 Iterator* TableCache::NewIterator(const ReadOptions& options,
+                                  const EnvOptions& toptions,
                                  uint64_t file_number,
                                  uint64_t file_size,
-                                  Table** tableptr) {
+                                  Table** tableptr,
+                                  bool for_compaction) {
  if (tableptr != nullptr) {
    *tableptr = nullptr;
  }

  Cache::Handle* handle = nullptr;
-  Status s = FindTable(file_number, file_size, &handle);
+  Status s = FindTable(toptions, file_number, file_size, &handle);
  if (!s.ok()) {
    return NewErrorIterator(s);
  }

  Table* table =
-    reinterpret_cast<TableAndFile*>(cache_->Value(handle))->table.get();
+    reinterpret_cast<Table*>(cache_->Value(handle));
  Iterator* result = table->NewIterator(options);
  result->RegisterCleanup(&UnrefEntry, cache_.get(), handle);
  if (tableptr != nullptr) {
    *tableptr = table;
  }
+
+  if (for_compaction) {
+    table->SetupForCompaction();
+  }
+
  return result;
 }

@@ -108,15 +115,22 @@ Status TableCache::Get(const ReadOptions& options,
                       uint64_t file_size,
                       const Slice& k,
                       void* arg,
-                       void (*saver)(void*, const Slice&, const Slice&, bool),
-                       bool* tableIO) {
+                       bool (*saver)(void*, const Slice&, const Slice&, bool),
+                       bool* table_io,
+                       void (*mark_key_may_exist)(void*),
+                       const bool no_io) {
  Cache::Handle* handle = nullptr;
-  Status s = FindTable(file_number, file_size, &handle, tableIO);
+  Status s = FindTable(storage_options_, file_number, file_size,
+                       &handle, table_io, no_io);
  if (s.ok()) {
    Table* t =
-      reinterpret_cast<TableAndFile*>(cache_->Value(handle))->table.get();
-    s = t->InternalGet(options, k, arg, saver);
+      reinterpret_cast<Table*>(cache_->Value(handle));
+    s = t->InternalGet(options, k, arg, saver, mark_key_may_exist, no_io);
    cache_->Release(handle);
+  } else if (no_io && s.IsNotFound()) {
+    // Couldnt find Table in cache but treat as kFound if no_io set
+    (*mark_key_may_exist)(arg);
+    return Status::OK();
  }
  return s;
 }
@@ -10,9 +10,10 @@
 #include <string>
 #include <stdint.h>
 #include "db/dbformat.h"
+#include "leveldb/env.h"
 #include "leveldb/cache.h"
-#include "leveldb/table.h"
 #include "port/port.h"
+#include "table/table.h"

 namespace leveldb {

@@ -20,7 +21,8 @@ class Env;

 class TableCache {
 public:
-  TableCache(const std::string& dbname, const Options* options, int entries);
+  TableCache(const std::string& dbname, const Options* options,
+             const EnvOptions& storage_options, int entries);
  ~TableCache();

  // Return an iterator for the specified file number (the corresponding
@@ -31,19 +33,24 @@ class TableCache {
  // the cache and should not be deleted, and is valid for as long as the
  // returned iterator is live.
  Iterator* NewIterator(const ReadOptions& options,
+                        const EnvOptions& toptions,
                        uint64_t file_number,
                        uint64_t file_size,
-                        Table** tableptr = nullptr);
+                        Table** tableptr = nullptr,
+                        bool for_compaction = false);

  // If a seek to internal key "k" in specified file finds an entry,
-  // call (*handle_result)(arg, found_key, found_value).
+  // call (*handle_result)(arg, found_key, found_value) repeatedly until
+  // it returns false.
  Status Get(const ReadOptions& options,
             uint64_t file_number,
             uint64_t file_size,
             const Slice& k,
             void* arg,
-             void (*handle_result)(void*, const Slice&, const Slice&, bool),
-             bool* tableIO);
+             bool (*handle_result)(void*, const Slice&, const Slice&, bool),
+             bool* table_io,
+             void (*mark_key_may_exist)(void*) = nullptr,
+             const bool no_io = false);

  // Evict any entry for the specified file number
  void Evict(uint64_t file_number);
@@ -52,10 +59,12 @@ class TableCache {
  Env* const env_;
  const std::string dbname_;
  const Options* options_;
+  const EnvOptions& storage_options_;
  std::shared_ptr<Cache> cache_;

-  Status FindTable(uint64_t file_number, uint64_t file_size, Cache::Handle**,
-                   bool* tableIO = nullptr);
+  Status FindTable(const EnvOptions& toptions, uint64_t file_number,
+                   uint64_t file_size, Cache::Handle**, bool* table_io=nullptr,
+                   const bool no_io = false);
 };

 }  // namespace leveldb
@@ -0,0 +1,171 @@
+#include "db/transaction_log_impl.h"
+#include "db/write_batch_internal.h"
+
+namespace leveldb {
+
+TransactionLogIteratorImpl::TransactionLogIteratorImpl(
+                           const std::string& dbname,
+                           const Options* options,
+                           const EnvOptions& soptions,
+                           const SequenceNumber seq,
+                           std::unique_ptr<VectorLogPtr> files,
+                           SequenceNumber const * const lastFlushedSequence) :
+    dbname_(dbname),
+    options_(options),
+    soptions_(soptions),
+    startingSequenceNumber_(seq),
+    files_(std::move(files)),
+    started_(false),
+    isValid_(false),
+    currentFileIndex_(0),
+    lastFlushedSequence_(lastFlushedSequence) {
+  assert(startingSequenceNumber_ <= *lastFlushedSequence_);
+  assert(files_.get() != nullptr);
+
+  reporter_.env = options_->env;
+  reporter_.info_log = options_->info_log.get();
+}
+
+Status TransactionLogIteratorImpl::OpenLogFile(
+  const LogFile* logFile,
+  unique_ptr<SequentialFile>* file) {
+  Env* env = options_->env;
+  if (logFile->Type() == kArchivedLogFile) {
+    std::string fname = ArchivedLogFileName(dbname_, logFile->LogNumber());
+    return env->NewSequentialFile(fname, file, soptions_);
+  } else {
+    std::string fname = LogFileName(dbname_, logFile->LogNumber());
+    Status status = env->NewSequentialFile(fname, file, soptions_);
+    if (!status.ok()) {
+      //  If cannot open file in DB directory.
+      //  Try the archive dir, as it could have moved in the meanwhile.
+      fname = ArchivedLogFileName(dbname_, logFile->LogNumber());
+      status = env->NewSequentialFile(fname, file, soptions_);
+      if (!status.ok()) {
+        return Status::IOError(" Requested file not present in the dir");
+      }
+    }
+    return status;
+  }
+}
+
+BatchResult TransactionLogIteratorImpl::GetBatch()  {
+  assert(isValid_);  //  cannot call in a non valid state.
+  BatchResult result;
+  result.sequence = currentSequence_;
+  result.writeBatchPtr = std::move(currentBatch_);
+  return result;
+}
+
+Status TransactionLogIteratorImpl::status() {
+  return currentStatus_;
+}
+
+bool TransactionLogIteratorImpl::Valid() {
+  return started_ && isValid_;
+}
+
+void TransactionLogIteratorImpl::Next() {
+  LogFile* currentLogFile = files_.get()->at(currentFileIndex_).get();
+
+//  First seek to the given seqNo. in the current file.
+  std::string scratch;
+  Slice record;
+  if (!started_) {
+    started_ = true;  // this piece only runs onced.
+    isValid_ = false;
+    if (startingSequenceNumber_ > *lastFlushedSequence_) {
+      currentStatus_ = Status::IOError("Looking for a sequence, "
+                                        "which is not flushed yet.");
+      return;
+    }
+    Status s = OpenLogReader(currentLogFile);
+    if (!s.ok()) {
+      currentStatus_ = s;
+      isValid_ = false;
+      return;
+    }
+    while (currentLogReader_->ReadRecord(&record, &scratch)) {
+      if (record.size() < 12) {
+        reporter_.Corruption(
+          record.size(), Status::Corruption("log record too small"));
+        continue;
+      }
+      UpdateCurrentWriteBatch(record);
+      if (currentSequence_ >= startingSequenceNumber_) {
+        assert(currentSequence_ <= *lastFlushedSequence_);
+        isValid_ = true;
+        break;
+      } else {
+        isValid_ = false;
+      }
+    }
+    if (isValid_) {
+      // Done for this iteration
+      return;
+    }
+  }
+  bool openNextFile = true;
+  while(openNextFile) {
+    assert(currentLogReader_);
+    if (currentSequence_ < *lastFlushedSequence_) {
+      if (currentLogReader_->IsEOF()) {
+        currentLogReader_->UnmarkEOF();
+      }
+      while (currentLogReader_->ReadRecord(&record, &scratch)) {
+        if (record.size() < 12) {
+          reporter_.Corruption(
+            record.size(), Status::Corruption("log record too small"));
+          continue;
+        } else {
+          UpdateCurrentWriteBatch(record);
+          openNextFile = false;
+          break;
+        }
+      }
+    }
+
+    if (openNextFile) {
+      if (currentFileIndex_ < files_.get()->size() - 1) {
+        ++currentFileIndex_;
+        Status status =OpenLogReader(files_.get()->at(currentFileIndex_).get());
+        if (!status.ok()) {
+          isValid_ = false;
+          currentStatus_ = status;
+          return;
+        }
+      } else {
+        isValid_ = false;
+        openNextFile = false;
+        if (currentSequence_ == *lastFlushedSequence_) {
+          currentStatus_ = Status::OK();
+        } else {
+          currentStatus_ = Status::IOError(" NO MORE DATA LEFT");
+        }
+      }
+    }
+  }
+}
+
+void TransactionLogIteratorImpl::UpdateCurrentWriteBatch(const Slice& record) {
+  WriteBatch* batch = new WriteBatch();
+  WriteBatchInternal::SetContents(batch, record);
+  currentSequence_ = WriteBatchInternal::Sequence(batch);
+  currentBatch_.reset(batch);
+  isValid_ = true;
+  currentStatus_ = Status::OK();
+}
+
+Status TransactionLogIteratorImpl::OpenLogReader(const LogFile* logFile) {
+  unique_ptr<SequentialFile> file;
+  Status status = OpenLogFile(logFile, &file);
+  if (!status.ok()) {
+    return status;
+  }
+  assert(file);
+  currentLogReader_.reset(
+    new log::Reader(std::move(file), &reporter_, true, 0)
+  );
+  return Status::OK();
+}
+}  //  namespace leveldb
@@ -7,35 +7,61 @@
 #include "leveldb/env.h"
 #include "leveldb/options.h"
 #include "leveldb/types.h"
-#include "leveldb/transaction_log_iterator.h"
-#include "db/log_file.h"
+#include "leveldb/transaction_log.h"
 #include "db/log_reader.h"
+#include "db/filename.h"

 namespace leveldb {

 struct LogReporter : public log::Reader::Reporter {
  Env* env;
  Logger* info_log;
-  uint64_t log_number;
  virtual void Corruption(size_t bytes, const Status& s) {
-    Log(info_log, "%ld: dropping %d bytes; %s",
-        log_number, static_cast<int>(bytes), s.ToString().c_str());
+    Log(info_log, "dropping %zu bytes; %s", bytes, s.ToString().c_str());
  }
 };

+class LogFileImpl : public LogFile {
+ public:
+  LogFileImpl(uint64_t logNum, WalFileType logType, SequenceNumber startSeq,
+              uint64_t sizeBytes) :
+    logNumber_(logNum),
+    type_(logType),
+    startSequence_(startSeq),
+    sizeFileBytes_(sizeBytes) {
+  }
+
+  std::string Filename() const { return LogFileName("", logNumber_); }
+
+  uint64_t LogNumber() const { return logNumber_; }
+
+  WalFileType Type() const { return type_; }
+
+  SequenceNumber StartSequence() const { return startSequence_; }
+
+  uint64_t SizeFileBytes() const { return sizeFileBytes_; }
+
+  bool operator < (const LogFile& that) const {
+    return LogNumber() < that.LogNumber();
+  }
+
+ private:
+  uint64_t logNumber_;
+  WalFileType type_;
+  SequenceNumber startSequence_;
+  uint64_t sizeFileBytes_;
+
+};
+
 class TransactionLogIteratorImpl : public TransactionLogIterator {
 public:
  TransactionLogIteratorImpl(const std::string& dbname,
                             const Options* options,
-                             SequenceNumber& seqNum,
-                             std::vector<LogFile>* files,
+                             const EnvOptions& soptions,
+                             const SequenceNumber seqNum,
+                             std::unique_ptr<VectorLogPtr> files,
                             SequenceNumber const * const lastFlushedSequence);

-  virtual ~TransactionLogIteratorImpl() {
-    //  TODO move to cc file.
-    delete files_;
-  }
-
  virtual bool Valid();

  virtual void Next();
@@ -47,21 +73,23 @@ class TransactionLogIteratorImpl : public TransactionLogIterator {
 private:
  const std::string& dbname_;
  const Options* options_;
-  const uint64_t sequenceNumber_;
-  const std::vector<LogFile>* files_;
+  const EnvOptions& soptions_;
+  const SequenceNumber startingSequenceNumber_;
+  std::unique_ptr<VectorLogPtr> files_;
  bool started_;
  bool isValid_;  // not valid when it starts of.
  Status currentStatus_;
  size_t currentFileIndex_;
  std::unique_ptr<WriteBatch> currentBatch_;
  unique_ptr<log::Reader> currentLogReader_;
-  Status OpenLogFile(const LogFile& logFile, unique_ptr<SequentialFile>* file);
-  LogReporter NewLogReporter(uint64_t logNumber);
+  Status OpenLogFile(const LogFile* logFile, unique_ptr<SequentialFile>* file);
+  LogReporter reporter_;
  SequenceNumber const * const lastFlushedSequence_;
  // represents the sequence number being read currently.
  SequenceNumber currentSequence_;

  void UpdateCurrentWriteBatch(const Slice& record);
+  Status OpenLogReader(const LogFile* file);
 };


@@ -1,172 +0,0 @@
-#include "db/transaction_log_iterator_impl.h"
-#include "db/write_batch_internal.h"
-#include "db/filename.h"
-namespace leveldb {
-
-TransactionLogIteratorImpl::TransactionLogIteratorImpl(
-                           const std::string& dbname,
-                           const Options* options,
-                           SequenceNumber& seq,
-                           std::vector<LogFile>* files,
-                           SequenceNumber const * const lastFlushedSequence) :
-  dbname_(dbname),
-  options_(options),
-  sequenceNumber_(seq),
-  files_(files),
-  started_(false),
-  isValid_(true),
-  currentFileIndex_(0),
-  lastFlushedSequence_(lastFlushedSequence) {
-  assert(files_ != nullptr);
-  assert(lastFlushedSequence_);
-}
-
-LogReporter
-TransactionLogIteratorImpl::NewLogReporter(const uint64_t logNumber) {
-  LogReporter reporter;
-  reporter.env = options_->env;
-  reporter.info_log = options_->info_log.get();
-  reporter.log_number = logNumber;
-  return reporter;
-}
-
-Status TransactionLogIteratorImpl::OpenLogFile(
-  const LogFile& logFile,
-  unique_ptr<SequentialFile>* file) {
-  Env* env = options_->env;
-  if (logFile.type == kArchivedLogFile) {
-    std::string fname = ArchivedLogFileName(dbname_, logFile.logNumber);
-    return env->NewSequentialFile(fname, file);
-  } else {
-    std::string fname = LogFileName(dbname_, logFile.logNumber);
-    Status status = env->NewSequentialFile(fname, file);
-    if (!status.ok()) {
-      //  If cannot open file in DB directory.
-      //  Try the archive dir, as it could have moved in the meanwhile.
-      fname = ArchivedLogFileName(dbname_, logFile.logNumber);
-      status = env->NewSequentialFile(fname, file);
-      if (!status.ok()) {
-        return Status::IOError(" Requested file not present in the dir");
-      }
-    }
-    return status;
-  }
-}
-
-BatchResult TransactionLogIteratorImpl::GetBatch()  {
-  assert(isValid_);  //  cannot call in a non valid state.
-  BatchResult result;
-  result.sequence = currentSequence_;
-  result.writeBatchPtr = std::move(currentBatch_);
-  return result;
-}
-
-Status TransactionLogIteratorImpl::status() {
-  return currentStatus_;
-}
-
-bool TransactionLogIteratorImpl::Valid() {
-  return started_ && isValid_;
-}
-
-void TransactionLogIteratorImpl::Next() {
-//  First seek to the given seqNo. in the current file.
-  LogFile currentLogFile = files_->at(currentFileIndex_);
-  LogReporter reporter = NewLogReporter(currentLogFile.logNumber);
-  std::string scratch;
-  Slice record;
-
-  if (!started_) {
-    isValid_ = false;
-    if (sequenceNumber_ > *lastFlushedSequence_) {
-      currentStatus_ = Status::IOError("Looking for a sequence, "
-                                        "which is not flushed yet.");
-      return;
-    }
-    unique_ptr<SequentialFile> file;
-    Status status = OpenLogFile(currentLogFile, &file);
-    if (!status.ok()) {
-      currentStatus_ = status;
-      return;
-    }
-    assert(file);
-    unique_ptr<log::Reader> reader(
-      new log::Reader(std::move(file), &reporter, true, 0));
-    assert(reader);
-    while (reader->ReadRecord(&record, &scratch)) {
-      if (record.size() < 12) {
-        reporter.Corruption(
-          record.size(), Status::Corruption("log record too small"));
-        continue;
-      }
-      UpdateCurrentWriteBatch(record);
-      if (currentSequence_ >= sequenceNumber_) {
-        assert(currentSequence_ < *lastFlushedSequence_);
-        isValid_ = true;
-        currentLogReader_ = std::move(reader);
-        break;
-      }
-    }
-    if (!isValid_) {
-      //  TODO read the entire first file. and did not find the seq number.
-      //  Error out.
-      currentStatus_ =
-        Status::NotFound("Did not find the Seq no. in first file");
-    }
-    started_ = true;
-  } else {
-LOOK_NEXT_FILE:
-    assert(currentLogReader_);
-    bool openNextFile = true;
-
-    if (currentSequence_ == *lastFlushedSequence_) {
-      // The last update has been read. and next is being called.
-      isValid_ = false;
-      currentStatus_ = Status::OK();
-    }
-
-    while (currentLogReader_->ReadRecord(&record, &scratch) &&
-           currentSequence_ < *lastFlushedSequence_) {
-      if (record.size() < 12) {
-        reporter.Corruption(
-          record.size(), Status::Corruption("log record too small"));
-        continue;
-      } else {
-        UpdateCurrentWriteBatch(record);
-        openNextFile = false;
-        break;
-      }
-    }
-
-    if (openNextFile) {
-      if (currentFileIndex_ < files_->size() - 1) {
-        ++currentFileIndex_;
-        currentLogReader_.reset();
-        unique_ptr<SequentialFile> file;
-        Status status = OpenLogFile(files_->at(currentFileIndex_), &file);
-        if (!status.ok()) {
-          isValid_ = false;
-          currentStatus_ = status;
-          return;
-        }
-        currentLogReader_.reset(
-          new log::Reader(std::move(file), &reporter, true, 0));
-        goto LOOK_NEXT_FILE;
-      } else {
-        //  LOOKED AT FILES. WE ARE DONE HERE.
-        isValid_ = false;
-        currentStatus_ = Status::IOError(" NO MORE DATA LEFT");
-      }
-    }
-
-  }
-}
-
-void TransactionLogIteratorImpl::UpdateCurrentWriteBatch(const Slice& record) {
-  WriteBatch* batch = new WriteBatch();
-  WriteBatchInternal::SetContents(batch, record);
-  currentSequence_ = WriteBatchInternal::Sequence(batch);
-  currentBatch_.reset(batch);
-}
-
-}  //  namespace leveldb
@@ -20,7 +20,10 @@ enum Tag {
  kDeletedFile          = 6,
  kNewFile              = 7,
  // 8 was used for large value refs
-  kPrevLogNumber        = 9
+  kPrevLogNumber        = 9,
+
+  // these are new formats divergent from open source leveldb
+  kNewFile2             = 100  // store smallest & largest seqno
 };

 void VersionEdit::Clear() {
@@ -76,12 +79,14 @@ void VersionEdit::EncodeTo(std::string* dst) const {

  for (size_t i = 0; i < new_files_.size(); i++) {
    const FileMetaData& f = new_files_[i].second;
-    PutVarint32(dst, kNewFile);
+    PutVarint32(dst, kNewFile2);
    PutVarint32(dst, new_files_[i].first);  // level
    PutVarint64(dst, f.number);
    PutVarint64(dst, f.file_size);
    PutLengthPrefixedSlice(dst, f.smallest.Encode());
    PutLengthPrefixedSlice(dst, f.largest.Encode());
+    PutVarint64(dst, f.smallest_seqno);
+    PutVarint64(dst, f.largest_seqno);
  }
 }

@@ -201,6 +206,22 @@ Status VersionEdit::DecodeFrom(const Slice& src) {
        }
        break;

+      case kNewFile2:
+        if (GetLevel(&input, &level, &msg) &&
+            GetVarint64(&input, &f.number) &&
+            GetVarint64(&input, &f.file_size) &&
+            GetInternalKey(&input, &f.smallest) &&
+            GetInternalKey(&input, &f.largest) &&
+            GetVarint64(&input, &f.smallest_seqno) &&
+            GetVarint64(&input, &f.largest_seqno) ) {
+          new_files_.push_back(std::make_pair(level, f));
+        } else {
+          if (!msg) {
+            msg = "new-file2 entry";
+          }
+        }
+        break;
+
      default:
        msg = "unknown tag";
        break;
@@ -218,7 +239,7 @@ Status VersionEdit::DecodeFrom(const Slice& src) {
  return result;
 }

-std::string VersionEdit::DebugString() const {
+std::string VersionEdit::DebugString(bool hex_key) const {
  std::string r;
  r.append("VersionEdit {");
  if (has_comparator_) {
@@ -245,7 +266,7 @@ std::string VersionEdit::DebugString() const {
    r.append("\n  CompactPointer: ");
    AppendNumberTo(&r, compact_pointers_[i].first);
    r.append(" ");
-    r.append(compact_pointers_[i].second.DebugString());
+    r.append(compact_pointers_[i].second.DebugString(hex_key));
  }
  for (DeletedFileSet::const_iterator iter = deleted_files_.begin();
       iter != deleted_files_.end();
@@ -264,9 +285,9 @@ std::string VersionEdit::DebugString() const {
    r.append(" ");
    AppendNumberTo(&r, f.file_size);
    r.append(" ");
-    r.append(f.smallest.DebugString());
+    r.append(f.smallest.DebugString(hex_key));
    r.append(" .. ");
-    r.append(f.largest.DebugString());
+    r.append(f.largest.DebugString(hex_key));
  }
  r.append("\n}\n");
  return r;
@@ -22,6 +22,8 @@ struct FileMetaData {
  InternalKey smallest;       // Smallest internal key served by table
  InternalKey largest;        // Largest internal key served by table
  bool being_compacted;       // Is this file undergoing compaction?
+  SequenceNumber smallest_seqno;// The smallest seqno in this file
+  SequenceNumber largest_seqno; // The largest seqno in this file

  FileMetaData() : refs(0), allowed_seeks(1 << 30), file_size(0),
                   being_compacted(false) { }
@@ -67,12 +69,17 @@ class VersionEdit {
  void AddFile(int level, uint64_t file,
               uint64_t file_size,
               const InternalKey& smallest,
-               const InternalKey& largest) {
+               const InternalKey& largest,
+               const SequenceNumber& smallest_seqno,
+               const SequenceNumber& largest_seqno) {
    FileMetaData f;
    f.number = file;
    f.file_size = file_size;
    f.smallest = smallest;
    f.largest = largest;
+    f.smallest_seqno = smallest_seqno;
+    f.largest_seqno = largest_seqno;
+    assert(smallest_seqno <= largest_seqno);
    new_files_.push_back(std::make_pair(level, f));
  }

@@ -81,10 +88,15 @@ class VersionEdit {
    deleted_files_.insert(std::make_pair(level, file));
  }

+  // Number of edits
+  int NumEntries() {
+    return new_files_.size() + deleted_files_.size();
+  }
+
  void EncodeTo(std::string* dst) const;
  Status DecodeFrom(const Slice& src);

-  std::string DebugString() const;
+  std::string DebugString(bool hex_key = false) const;

 private:
  friend class VersionSet;
@@ -27,7 +27,9 @@ TEST(VersionEditTest, EncodeDecode) {
    TestEncodeDecode(edit);
    edit.AddFile(3, kBig + 300 + i, kBig + 400 + i,
                 InternalKey("foo", kBig + 500 + i, kTypeValue),
-                 InternalKey("zoo", kBig + 600 + i, kTypeDeletion));
+                 InternalKey("zoo", kBig + 600 + i, kTypeDeletion),
+                 kBig + 500 + i,
+                 kBig + 600 + i);
    edit.DeleteFile(4, kBig + 700 + i);
    edit.SetCompactPointer(i, InternalKey("x", kBig + 900 + i, kTypeValue));
  }
@@ -63,17 +63,21 @@ class Version {
  // Append to *iters a sequence of iterators that will
  // yield the contents of this Version when merged together.
  // REQUIRES: This version has been saved (see VersionSet::SaveTo)
-  void AddIterators(const ReadOptions&, std::vector<Iterator*>* iters);
+  void AddIterators(const ReadOptions&, const EnvOptions& soptions,
+                    std::vector<Iterator*>* iters);

  // Lookup the value for key.  If found, store it in *val and
  // return OK.  Else return a non-OK status.  Fills *stats.
+  // Uses *operands to store merge_operator operations to apply later
  // REQUIRES: lock is not held
  struct GetStats {
    FileMetaData* seek_file;
    int seek_file_level;
  };
-  Status Get(const ReadOptions&, const LookupKey& key, std::string* val,
-             GetStats* stats);
+  void Get(const ReadOptions&, const LookupKey& key, std::string* val,
+           Status* status, std::deque<std::string>* operands, GetStats* stats,
+           const Options& db_option, const bool no_io = false,
+           bool* value_found = nullptr);

  // Adds "stats" into the current state.  Returns true if a new
  // compaction may need to be triggered, false otherwise.
@@ -106,7 +110,7 @@ class Version {
      const Slice& begin,         // nullptr means before all keys
      const Slice& end,           // nullptr means after all keys
      std::vector<FileMetaData*>* inputs,
-      int index);                 // start extending from this index
+      unsigned int index);                 // start extending from this index

  // Returns true iff some file in the specified level overlaps
  // some part of [*smallest_user_key,*largest_user_key].
@@ -116,6 +120,14 @@ class Version {
                      const Slice* smallest_user_key,
                      const Slice* largest_user_key);

+  // Returns true iff the first or last file in inputs contains
+  // an overlapping user key to the file "just outside" of it (i.e.
+  // just after the last file, or just before the first file)
+  // REQUIRES: "*inputs" is a sorted list of non-overlapping files
+  bool HasOverlappingUserKey(const std::vector<FileMetaData*>* inputs,
+                             int level);
+
+
  // Return the level at which we should place a new memtable compaction
  // result that covers the range [smallest_user_key,largest_user_key].
  int PickLevelForMemTableOutput(const Slice& smallest_user_key,
@@ -134,9 +146,12 @@ class Version {
 private:
  friend class Compaction;
  friend class VersionSet;
+  friend class DBImpl;

  class LevelFileNumIterator;
-  Iterator* NewConcatenatingIterator(const ReadOptions&, int level) const;
+  Iterator* NewConcatenatingIterator(const ReadOptions&,
+                                     const EnvOptions& soptions,
+                                     int level) const;

  VersionSet* vset_;            // VersionSet to which this Version belongs
  Version* next_;               // Next version in linked list
@@ -204,6 +219,7 @@ class VersionSet {
 public:
  VersionSet(const std::string& dbname,
             const Options* options,
+             const EnvOptions& storage_options,
             TableCache* table_cache,
             const InternalKeyComparator*);
  ~VersionSet();
@@ -322,8 +338,7 @@ class VersionSet {
  }

  // Add all files listed in any live version to *live.
-  // May also mutate some internal state.
-  void AddLiveFiles(std::set<uint64_t>* live);
+  void AddLiveFiles(std::vector<uint64_t>* live_list);

  // Add all files listed in the current version to *live.
  void AddLiveFilesCurrentVersion(std::set<uint64_t>* live);
@@ -337,6 +352,9 @@ class VersionSet {
  struct LevelSummaryStorage {
    char buffer[100];
  };
+  struct FileSummaryStorage {
+    char buffer[1000];
+  };
  const char* LevelSummary(LevelSummaryStorage* scratch) const;

  // printf contents (for debugging)
@@ -347,6 +365,10 @@ class VersionSet {
  // of files per level.  Uses *scratch as backing store.
  const char* LevelDataSizeSummary(LevelSummaryStorage* scratch) const;

+  // Return a human-readable short (single-line) summary of files
+  // in a specified level.  Uses *scratch as backing store.
+  const char* LevelFileSummary(FileSummaryStorage* scratch, int level) const;
+
  // Return the size of the current manifest file
  const uint64_t ManifestFileSize() { return current_->offset_manifest_file_; }

@@ -356,6 +378,9 @@ class VersionSet {
  // function will return nullptr.
  Compaction* PickCompactionBySize(int level, double score);

+  // Pick files to compact in Universal mode
+  Compaction* PickCompactionUniversal(int level, double score);
+
  // Free up the files that were participated in a compaction
  void ReleaseCompactionFiles(Compaction* c, Status status);

@@ -378,6 +403,8 @@ class VersionSet {
  // Get the max file size in a given level.
  uint64_t MaxFileSizeForLevel(int level);

+  double MaxBytesForLevel(int level);
+
 private:
  class Builder;
  struct ManifestWriter;
@@ -398,6 +425,8 @@ class VersionSet {
                 InternalKey* smallest,
                 InternalKey* largest);

+  void ExpandWhileOverlapping(Compaction* c);
+
  void SetupOtherInputs(Compaction* c);

  // Save current contents to *log
@@ -407,11 +436,9 @@ class VersionSet {

  bool ManifestContains(const std::string& record) const;

-  double MaxBytesForLevel(int level);
+  uint64_t ExpandedCompactionByteSizeLimit(int level);

-  int64_t ExpandedCompactionByteSizeLimit(int level);
-
-  int64_t MaxGrandParentOverlapBytes(int level);
+  uint64_t MaxGrandParentOverlapBytes(int level);

  Env* const env_;
  const std::string dbname_;
@@ -454,6 +481,13 @@ class VersionSet {
  // Save us the cost of checking file size twice in LogAndApply
  uint64_t last_observed_manifest_size_;

+  // storage options for all reads and writes except compactions
+  const EnvOptions& storage_options_;
+
+  // storage options used for compactions. This is a copy of
+  // storage_options_ but with readaheads set to readahead_compactions_.
+  const EnvOptions storage_options_compactions_;
+
  // No copying allowed
  VersionSet(const VersionSet&);
  void operator=(const VersionSet&);
@@ -479,9 +513,12 @@ class Compaction {
  ~Compaction();

  // Return the level that is being compacted.  Inputs from "level"
-  // and "level+1" will be merged to produce a set of "level+1" files.
+  // will be merged.
  int level() const { return level_; }

+  // Outputs will go to this level
+  int output_level() const { return out_level_; }
+
  // Return the object that holds the edits to the descriptor done
  // by this compaction.
  VersionEdit* edit() { return edit_; }
@@ -520,17 +557,21 @@ class Compaction {
  // Return the score that was used to pick this compaction run.
  double score() const { return score_; }

+  // Is this compaction creating a file in the bottom most level?
+  bool BottomMostLevel() { return bottommost_level_; }
+
 private:
  friend class Version;
  friend class VersionSet;

-  explicit Compaction(int level, uint64_t target_file_size,
+  explicit Compaction(int level, int out_level, uint64_t target_file_size,
    uint64_t max_grandparent_overlap_bytes, int number_levels,
    bool seek_compaction = false);

  int level_;
+  int out_level_; // levels to which output files are stored
  uint64_t max_output_file_size_;
-  int64_t maxGrandParentOverlapBytes_;
+  uint64_t maxGrandParentOverlapBytes_;
  Version* input_version_;
  VersionEdit* edit_;
  int number_levels_;
@@ -545,23 +586,27 @@ class Compaction {
  std::vector<FileMetaData*> grandparents_;
  size_t grandparent_index_;  // Index in grandparent_starts_
  bool seen_key_;             // Some output key has been seen
-  int64_t overlapped_bytes_;  // Bytes of overlap between current output
+  uint64_t overlapped_bytes_;  // Bytes of overlap between current output
                              // and grandparent files
  int base_index_;   // index of the file in files_[level_]
  int parent_index_; // index of some file with same range in files_[level_+1]
  double score_;     // score that was used to pick this compaction.

-  // State for implementing IsBaseLevelForKey
+  // Is this compaction creating a file in the bottom most level?
+  bool bottommost_level_;

  // level_ptrs_ holds indices into input_version_->levels_: our state
  // is that we are positioned at one of the file ranges for each
  // higher level than the ones involved in this compaction (i.e. for
  // all L >= level_ + 2).
-  size_t* level_ptrs_;
+  std::vector<size_t> level_ptrs_;

  // mark (or clear) all files that are being compacted
  void MarkFilesBeingCompacted(bool);

+  // Initialize whether compaction producing files at the bottommost level
+  void SetupBottomMostLevel(bool isManual);
+
  // In case of compaction error, reset the nextIndex that is used
  // to pick up the next file to be compacted from files_by_size_
  void ResetNextCompactionIndex();
@@ -7,7 +7,8 @@
 //    count: fixed32
 //    data: record[count]
 // record :=
-//    kTypeValue varstring varstring         |
+//    kTypeValue varstring varstring
+//    kTypeMerge varstring varstring
 //    kTypeDeletion varstring
 // varstring :=
 //    len: varint32
@@ -15,11 +16,15 @@

 #include "leveldb/write_batch.h"

-#include "leveldb/db.h"
+#include "leveldb/options.h"
+#include "leveldb/statistics.h"
 #include "db/dbformat.h"
+#include "db/db_impl.h"
 #include "db/memtable.h"
+#include "db/snapshot.h"
 #include "db/write_batch_internal.h"
 #include "util/coding.h"
+#include <stdexcept>

 namespace leveldb {

@@ -34,11 +39,24 @@ WriteBatch::~WriteBatch() { }

 WriteBatch::Handler::~Handler() { }

+void WriteBatch::Handler::Merge(const Slice& key, const Slice& value) {
+  throw std::runtime_error("Handler::Merge not implemented!");
+}
+
+void WriteBatch::Handler::LogData(const Slice& blob) {
+  // If the user has not specified something to do with blobs, then we ignore
+  // them.
+}
+
 void WriteBatch::Clear() {
  rep_.clear();
  rep_.resize(kHeader);
 }

+int WriteBatch::Count() const {
+  return WriteBatchInternal::Count(this);
+}
+
 Status WriteBatch::Iterate(Handler* handler) const {
  Slice input(rep_);
  if (input.size() < kHeader) {
@@ -46,10 +64,9 @@ Status WriteBatch::Iterate(Handler* handler) const {
  }

  input.remove_prefix(kHeader);
-  Slice key, value;
+  Slice key, value, blob;
  int found = 0;
  while (!input.empty()) {
-    found++;
    char tag = input[0];
    input.remove_prefix(1);
    switch (tag) {
@@ -57,6 +74,7 @@ Status WriteBatch::Iterate(Handler* handler) const {
        if (GetLengthPrefixedSlice(&input, &key) &&
            GetLengthPrefixedSlice(&input, &value)) {
          handler->Put(key, value);
+          found++;
        } else {
          return Status::Corruption("bad WriteBatch Put");
        }
@@ -64,10 +82,27 @@ Status WriteBatch::Iterate(Handler* handler) const {
      case kTypeDeletion:
        if (GetLengthPrefixedSlice(&input, &key)) {
          handler->Delete(key);
+          found++;
        } else {
          return Status::Corruption("bad WriteBatch Delete");
        }
        break;
+      case kTypeMerge:
+        if (GetLengthPrefixedSlice(&input, &key) &&
+            GetLengthPrefixedSlice(&input, &value)) {
+          handler->Merge(key, value);
+          found++;
+        } else {
+          return Status::Corruption("bad WriteBatch Merge");
+        }
+        break;
+      case kTypeLogData:
+        if (GetLengthPrefixedSlice(&input, &blob)) {
+          handler->LogData(blob);
+        } else {
+          return Status::Corruption("bad WriteBatch Blob");
+        }
+        break;
      default:
        return Status::Corruption("unknown WriteBatch tag");
    }
@@ -108,28 +143,72 @@ void WriteBatch::Delete(const Slice& key) {
  PutLengthPrefixedSlice(&rep_, key);
 }

+void WriteBatch::Merge(const Slice& key, const Slice& value) {
+  WriteBatchInternal::SetCount(this, WriteBatchInternal::Count(this) + 1);
+  rep_.push_back(static_cast<char>(kTypeMerge));
+  PutLengthPrefixedSlice(&rep_, key);
+  PutLengthPrefixedSlice(&rep_, value);
+}
+
+void WriteBatch::PutLogData(const Slice& blob) {
+  rep_.push_back(static_cast<char>(kTypeLogData));
+  PutLengthPrefixedSlice(&rep_, blob);
+}
+
 namespace {
 class MemTableInserter : public WriteBatch::Handler {
 public:
  SequenceNumber sequence_;
  MemTable* mem_;
+  const Options* options_;
+  DBImpl* db_;
+  const bool filter_deletes_;
+
+  MemTableInserter(SequenceNumber sequence, MemTable* mem, const Options* opts,
+                   DB* db, const bool filter_deletes)
+    : sequence_(sequence),
+      mem_(mem),
+      options_(opts),
+      db_(reinterpret_cast<DBImpl*>(db)),
+      filter_deletes_(filter_deletes) {
+    assert(mem_);
+    if (filter_deletes_) {
+      assert(options_);
+      assert(db_);
+    }
+  }

  virtual void Put(const Slice& key, const Slice& value) {
    mem_->Add(sequence_, kTypeValue, key, value);
    sequence_++;
  }
+  virtual void Merge(const Slice& key, const Slice& value) {
+    mem_->Add(sequence_, kTypeMerge, key, value);
+    sequence_++;
+  }
  virtual void Delete(const Slice& key) {
+    if (filter_deletes_) {
+      SnapshotImpl read_from_snapshot;
+      read_from_snapshot.number_ = sequence_;
+      ReadOptions ropts;
+      ropts.snapshot = &read_from_snapshot;
+      std::string value;
+      if (!db_->KeyMayExist(ropts, key, &value)) {
+        RecordTick(options_->statistics, NUMBER_FILTERED_DELETES);
+        return;
+      }
+    }
    mem_->Add(sequence_, kTypeDeletion, key, Slice());
    sequence_++;
  }
 };
 }  // namespace

-Status WriteBatchInternal::InsertInto(const WriteBatch* b,
-                                      MemTable* memtable) {
-  MemTableInserter inserter;
-  inserter.sequence_ = WriteBatchInternal::Sequence(b);
-  inserter.mem_ = memtable;
+Status WriteBatchInternal::InsertInto(const WriteBatch* b, MemTable* mem,
+                                      const Options* opts, DB* db,
+                                      const bool filter_deletes) {
+  MemTableInserter inserter(WriteBatchInternal::Sequence(b), mem, opts, db,
+                            filter_deletes);
  return b->Iterate(&inserter);
 }

@@ -7,6 +7,8 @@

 #include "leveldb/types.h"
 #include "leveldb/write_batch.h"
+#include "leveldb/db.h"
+#include "leveldb/options.h"

 namespace leveldb {

@@ -39,7 +41,12 @@ class WriteBatchInternal {

  static void SetContents(WriteBatch* batch, const Slice& contents);

-  static Status InsertInto(const WriteBatch* batch, MemTable* memtable);
+  // Inserts batch entries into memtable
+  // Drops deletes in batch if filter_del is set to true and
+  // db->KeyMayExist returns false
+  static Status InsertInto(const WriteBatch* batch, MemTable* memtable,
+                           const Options* opts = nullptr, DB* db = nullptr,
+                           const bool filter_del = false);

  static void Append(WriteBatch* dst, const WriteBatch* src);
 };
@@ -4,6 +4,8 @@

 #include "leveldb/db.h"

+#include <memory>
+#include "db/skiplistrep.h"
 #include "db/memtable.h"
 #include "db/write_batch_internal.h"
 #include "leveldb/env.h"
@@ -14,7 +16,8 @@ namespace leveldb {

 static std::string PrintContents(WriteBatch* b) {
  InternalKeyComparator cmp(BytewiseComparator());
-  MemTable* mem = new MemTable(cmp);
+  auto factory = std::make_shared<SkipListFactory>();
+  MemTable* mem = new MemTable(cmp, factory);
  mem->Ref();
  std::string state;
  Status s = WriteBatchInternal::InsertInto(b, mem);
@@ -33,19 +36,30 @@ static std::string PrintContents(WriteBatch* b) {
        state.append(")");
        count++;
        break;
+      case kTypeMerge:
+        state.append("Merge(");
+        state.append(ikey.user_key.ToString());
+        state.append(", ");
+        state.append(iter->value().ToString());
+        state.append(")");
+        count++;
+        break;
      case kTypeDeletion:
        state.append("Delete(");
        state.append(ikey.user_key.ToString());
        state.append(")");
        count++;
        break;
+      case kTypeLogData:
+        assert(false);
+        break;
    }
    state.append("@");
    state.append(NumberToString(ikey.sequence));
  }
  delete iter;
  if (!s.ok()) {
-    state.append("ParseError()");
+    state.append(s.ToString());
  } else if (count != WriteBatchInternal::Count(b)) {
    state.append("CountMismatch()");
  }
@@ -59,6 +73,7 @@ TEST(WriteBatchTest, Empty) {
  WriteBatch batch;
  ASSERT_EQ("", PrintContents(&batch));
  ASSERT_EQ(0, WriteBatchInternal::Count(&batch));
+  ASSERT_EQ(0, batch.Count());
 }

 TEST(WriteBatchTest, Multiple) {
@@ -73,6 +88,7 @@ TEST(WriteBatchTest, Multiple) {
            "Delete(box)@101"
            "Put(foo, bar)@100",
            PrintContents(&batch));
+  ASSERT_EQ(3, batch.Count());
 }

 TEST(WriteBatchTest, Corruption) {
@@ -84,7 +100,7 @@ TEST(WriteBatchTest, Corruption) {
  WriteBatchInternal::SetContents(&batch,
                                  Slice(contents.data(),contents.size()-1));
  ASSERT_EQ("Put(foo, bar)@200"
-            "ParseError()",
+            "Corruption: bad WriteBatch Delete",
            PrintContents(&batch));
 }

@@ -95,16 +111,19 @@ TEST(WriteBatchTest, Append) {
  WriteBatchInternal::Append(&b1, &b2);
  ASSERT_EQ("",
            PrintContents(&b1));
+  ASSERT_EQ(0, b1.Count());
  b2.Put("a", "va");
  WriteBatchInternal::Append(&b1, &b2);
  ASSERT_EQ("Put(a, va)@200",
            PrintContents(&b1));
+  ASSERT_EQ(1, b1.Count());
  b2.Clear();
  b2.Put("b", "vb");
  WriteBatchInternal::Append(&b1, &b2);
  ASSERT_EQ("Put(a, va)@200"
            "Put(b, vb)@201",
            PrintContents(&b1));
+  ASSERT_EQ(2, b1.Count());
  b2.Delete("foo");
  WriteBatchInternal::Append(&b1, &b2);
  ASSERT_EQ("Put(a, va)@200"
@@ -112,6 +131,51 @@ TEST(WriteBatchTest, Append) {
            "Put(b, vb)@201"
            "Delete(foo)@203",
            PrintContents(&b1));
+  ASSERT_EQ(4, b1.Count());
+}
+
+TEST(WriteBatchTest, Blob) {
+  WriteBatch batch;
+  batch.Put(Slice("k1"), Slice("v1"));
+  batch.Put(Slice("k2"), Slice("v2"));
+  batch.Put(Slice("k3"), Slice("v3"));
+  batch.PutLogData(Slice("blob1"));
+  batch.Delete(Slice("k2"));
+  batch.PutLogData(Slice("blob2"));
+  batch.Merge(Slice("foo"), Slice("bar"));
+  ASSERT_EQ(5, batch.Count());
+  ASSERT_EQ("Merge(foo, bar)@4"
+            "Put(k1, v1)@0"
+            "Delete(k2)@3"
+            "Put(k2, v2)@1"
+            "Put(k3, v3)@2",
+            PrintContents(&batch));
+
+  struct Handler : public WriteBatch::Handler {
+    std::string seen;
+    virtual void Put(const Slice& key, const Slice& value) {
+      seen += "Put(" + key.ToString() + ", " + value.ToString() + ")";
+    }
+    virtual void Merge(const Slice& key, const Slice& value) {
+      seen += "Merge(" + key.ToString() + ", " + value.ToString() + ")";
+    }
+    virtual void LogData(const Slice& blob) {
+      seen += "LogData(" + blob.ToString() + ")";
+    }
+    virtual void Delete(const Slice& key) {
+      seen += "Delete(" + key.ToString() + ")";
+    }
+  } handler;
+  batch.Iterate(&handler);
+  ASSERT_EQ(
+            "Put(k1, v1)"
+            "Put(k2, v2)"
+            "Put(k3, v3)"
+            "LogData(blob1)"
+            "Delete(k2)"
+            "LogData(blob2)"
+            "Merge(foo, bar)",
+            handler.seen);
 }

 }  // namespace leveldb
@@ -235,15 +235,18 @@ class HdfsEnv : public Env {
  }

  virtual Status NewSequentialFile(const std::string& fname,
-                                   unique_ptr<SequentialFile>* result);
+                                   unique_ptr<SequentialFile>* result,
+                                   const EnvOptions& options);

  virtual Status NewRandomAccessFile(const std::string& fname,
-                                     unique_ptr<RandomAccessFile>* result) {
+                                     unique_ptr<RandomAccessFile>* result,
+                                     const EnvOptions& options) {
    return notsup;
  }

  virtual Status NewWritableFile(const std::string& fname,
-                                 unique_ptr<WritableFile>* result) {
+                                 unique_ptr<WritableFile>* result,
+                                 const EnvOptions& options) {
    return notsup;
  }

@@ -233,7 +233,8 @@ class InMemoryEnv : public EnvWrapper {

  // Partial implementation of the Env interface.
  virtual Status NewSequentialFile(const std::string& fname,
-                                   unique_ptr<SequentialFile>* result) {
+                                   unique_ptr<SequentialFile>* result,
+                                   const EnvOptions& soptions) {
    MutexLock lock(&mutex_);
    if (file_map_.find(fname) == file_map_.end()) {
      *result = NULL;
@@ -245,7 +246,8 @@ class InMemoryEnv : public EnvWrapper {
  }

  virtual Status NewRandomAccessFile(const std::string& fname,
-                                     unique_ptr<RandomAccessFile>* result) {
+                                     unique_ptr<RandomAccessFile>* result,
+                                     const EnvOptions& soptions) {
    MutexLock lock(&mutex_);
    if (file_map_.find(fname) == file_map_.end()) {
      *result = NULL;
@@ -257,7 +259,8 @@ class InMemoryEnv : public EnvWrapper {
  }

  virtual Status NewWritableFile(const std::string& fname,
-                                 unique_ptr<WritableFile>* result) {
+                                 unique_ptr<WritableFile>* result,
+                                 const EnvOptions& soptions) {
    MutexLock lock(&mutex_);
    if (file_map_.find(fname) != file_map_.end()) {
      DeleteFileInternal(fname);
@@ -17,6 +17,7 @@ namespace leveldb {
 class MemEnvTest {
 public:
  Env* env_;
+  const EnvOptions soptions_;

  MemEnvTest()
      : env_(NewMemEnv(Env::Default())) {
@@ -40,7 +41,7 @@ TEST(MemEnvTest, Basics) {
  ASSERT_EQ(0U, children.size());

  // Create a file.
-  ASSERT_OK(env_->NewWritableFile("/dir/f", &writable_file));
+  ASSERT_OK(env_->NewWritableFile("/dir/f", &writable_file, soptions_));
  writable_file.reset();

  // Check that the file exists.
@@ -52,7 +53,7 @@ TEST(MemEnvTest, Basics) {
  ASSERT_EQ("f", children[0]);

  // Write to the file.
-  ASSERT_OK(env_->NewWritableFile("/dir/f", &writable_file));
+  ASSERT_OK(env_->NewWritableFile("/dir/f", &writable_file, soptions_));
  ASSERT_OK(writable_file->Append("abc"));
  writable_file.reset();

@@ -71,9 +72,11 @@ TEST(MemEnvTest, Basics) {
  // Check that opening non-existent file fails.
  unique_ptr<SequentialFile> seq_file;
  unique_ptr<RandomAccessFile> rand_file;
-  ASSERT_TRUE(!env_->NewSequentialFile("/dir/non_existent", &seq_file).ok());
+  ASSERT_TRUE(!env_->NewSequentialFile("/dir/non_existent", &seq_file,
+                                       soptions_).ok());
  ASSERT_TRUE(!seq_file);
-  ASSERT_TRUE(!env_->NewRandomAccessFile("/dir/non_existent", &rand_file).ok());
+  ASSERT_TRUE(!env_->NewRandomAccessFile("/dir/non_existent", &rand_file,
+                                         soptions_).ok());
  ASSERT_TRUE(!rand_file);

  // Check that deleting works.
@@ -94,13 +97,13 @@ TEST(MemEnvTest, ReadWrite) {

  ASSERT_OK(env_->CreateDir("/dir"));

-  ASSERT_OK(env_->NewWritableFile("/dir/f", &writable_file));
+  ASSERT_OK(env_->NewWritableFile("/dir/f", &writable_file, soptions_));
  ASSERT_OK(writable_file->Append("hello "));
  ASSERT_OK(writable_file->Append("world"));
  writable_file.reset();

  // Read sequentially.
-  ASSERT_OK(env_->NewSequentialFile("/dir/f", &seq_file));
+  ASSERT_OK(env_->NewSequentialFile("/dir/f", &seq_file, soptions_));
  ASSERT_OK(seq_file->Read(5, &result, scratch)); // Read "hello".
  ASSERT_EQ(0, result.compare("hello"));
  ASSERT_OK(seq_file->Skip(1));
@@ -113,7 +116,7 @@ TEST(MemEnvTest, ReadWrite) {
  ASSERT_EQ(0U, result.size());

  // Random reads.
-  ASSERT_OK(env_->NewRandomAccessFile("/dir/f", &rand_file));
+  ASSERT_OK(env_->NewRandomAccessFile("/dir/f", &rand_file, soptions_));
  ASSERT_OK(rand_file->Read(6, 5, &result, scratch)); // Read "world".
  ASSERT_EQ(0, result.compare("world"));
  ASSERT_OK(rand_file->Read(0, 5, &result, scratch)); // Read "hello".
@@ -139,7 +142,7 @@ TEST(MemEnvTest, Misc) {
  ASSERT_TRUE(!test_dir.empty());

  unique_ptr<WritableFile> writable_file;
-  ASSERT_OK(env_->NewWritableFile("/a/b", &writable_file));
+  ASSERT_OK(env_->NewWritableFile("/a/b", &writable_file, soptions_));

  // These are no-ops, but we test they return success.
  ASSERT_OK(writable_file->Sync());
@@ -158,14 +161,14 @@ TEST(MemEnvTest, LargeWrite) {
  }

  unique_ptr<WritableFile> writable_file;
-  ASSERT_OK(env_->NewWritableFile("/dir/f", &writable_file));
+  ASSERT_OK(env_->NewWritableFile("/dir/f", &writable_file, soptions_));
  ASSERT_OK(writable_file->Append("foo"));
  ASSERT_OK(writable_file->Append(write_data));
  writable_file.reset();

  unique_ptr<SequentialFile> seq_file;
  Slice result;
-  ASSERT_OK(env_->NewSequentialFile("/dir/f", &seq_file));
+  ASSERT_OK(env_->NewSequentialFile("/dir/f", &seq_file, soptions_));
  ASSERT_OK(seq_file->Read(3, &result, scratch)); // Read "foo".
  ASSERT_EQ(0, result.compare("foo"));

@@ -0,0 +1,38 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Arena class defines memory allocation methods. It's used by memtable and
+// skiplist.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_ARENA_H_
+#define STORAGE_LEVELDB_INCLUDE_ARENA_H_
+
+namespace leveldb {
+
+class Arena {
+ public:
+  Arena() {};
+  virtual ~Arena() {};
+
+  // Return a pointer to a newly allocated memory block of "bytes" bytes.
+  virtual char* Allocate(size_t bytes) = 0;
+
+  // Allocate memory with the normal alignment guarantees provided by malloc.
+  virtual char* AllocateAligned(size_t bytes) = 0;
+
+  // Returns an estimate of the total memory used by arena.
+  virtual const size_t ApproximateMemoryUsage() = 0;
+
+  // Returns the total number of bytes in all blocks allocated so far.
+  virtual const size_t MemoryAllocatedBytes() = 0;
+
+ private:
+  // No copying allowed
+  Arena(const Arena&);
+  void operator=(const Arena&);
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_ARENA_H_
@@ -0,0 +1,71 @@
+// Copyright (c) 2013 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_COMPACTION_FILTER_H_
+#define STORAGE_LEVELDB_INCLUDE_COMPACTION_FILTER_H_
+
+#include <string>
+
+namespace leveldb {
+
+class Slice;
+
+// CompactionFilter allows an application to modify/delete a key-value at
+// the time of compaction.
+
+class CompactionFilter {
+ public:
+  virtual ~CompactionFilter() {}
+
+
+  // The compaction process invokes this
+  // method for kv that is being compacted. A return value
+  // of false indicates that the kv should be preserved in the
+  // output of this compaction run and a return value of true
+  // indicates that this key-value should be removed from the
+  // output of the compaction.  The application can inspect
+  // the existing value of the key and make decision based on it.
+  //
+  // When the value is to be preserved, the application has the option
+  // to modify the existing_value and pass it back through new_value.
+  // value_changed needs to be set to true in this case.
+  virtual bool Filter(int level,
+                      const Slice& key,
+                      const Slice& existing_value,
+                      std::string* new_value,
+                      bool* value_changed) const = 0;
+
+  // Returns a name that identifies this compaction filter.
+  // The name will be printed to LOG file on start up for diagnosis.
+  virtual const char* Name() const = 0;
+};
+
+// Each compaction will create a new CompactionFilter allowing the
+// application to know about different campactions
+class CompactionFilterFactory {
+  public:
+    virtual ~CompactionFilterFactory() { };
+    virtual std::unique_ptr<CompactionFilter> CreateCompactionFilter() = 0;
+
+    // Returns a name that identifies this compaction filter factory.
+    virtual const char* Name() const = 0;
+};
+
+// Default implementaion of CompactionFilterFactory which does not
+// return any filter
+class DefaultCompactionFilterFactory : public CompactionFilterFactory {
+  public:
+    virtual std::unique_ptr<CompactionFilter>
+    CreateCompactionFilter() override {
+      return std::unique_ptr<CompactionFilter>(nullptr);
+    }
+
+    virtual const char* Name() const override {
+      return "DefaultCompactionFilterFactory";
+    }
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_COMPACTION_FILTER_H_
@@ -12,15 +12,15 @@
 #include "leveldb/iterator.h"
 #include "leveldb/options.h"
 #include "leveldb/types.h"
-#include "leveldb/transaction_log_iterator.h"
+#include "leveldb/transaction_log.h"

 namespace leveldb {

 using std::unique_ptr;

 // Update Makefile if you change these
-static const int kMajorVersion = 1;
-static const int kMinorVersion = 5;
+static const int kMajorVersion = 2;
+static const int kMinorVersion = 0;

 struct Options;
 struct ReadOptions;
@@ -83,6 +83,14 @@ class DB {
  // Note: consider setting options.sync = true.
  virtual Status Delete(const WriteOptions& options, const Slice& key) = 0;

+  // Merge the database entry for "key" with "value".  Returns OK on success,
+  // and a non-OK status on error. The semantics of this operation is
+  // determined by the user provided merge_operator when opening DB.
+  // Note: consider setting options.sync = true.
+  virtual Status Merge(const WriteOptions& options,
+                       const Slice& key,
+                       const Slice& value) = 0;
+
  // Apply the specified updates to the database.
  // Returns OK on success, non-OK on failure.
  // Note: consider setting options.sync = true.
@@ -96,7 +104,39 @@ class DB {
  //
  // May return some other Status on an error.
  virtual Status Get(const ReadOptions& options,
-                     const Slice& key, std::string* value) = 0;
+                     const Slice& key,
+                     std::string* value) = 0;
+
+  // If keys[i] does not exist in the database, then the i'th returned
+  // status will be one for which Status::IsNotFound() is true, and
+  // (*values)[i] will be set to some arbitrary value (often ""). Otherwise,
+  // the i'th returned status will have Status::ok() true, and (*values)[i]
+  // will store the value associated with keys[i].
+  //
+  // (*values) will always be resized to be the same size as (keys).
+  // Similarly, the number of returned statuses will be the number of keys.
+  // Note: keys will not be "de-duplicated". Duplicate keys will return
+  // duplicate values in order.
+  virtual std::vector<Status> MultiGet(const ReadOptions& options,
+                                       const std::vector<Slice>& keys,
+                                       std::vector<std::string>* values) = 0;
+
+  // If the key definitely does not exist in the database, then this method
+  // returns false, else true. If the caller wants to obtain value when the key
+  // is found in memory, a bool for 'value_found' must be passed. 'value_found'
+  // will be true on return if value has been set properly.
+  // This check is potentially lighter-weight than invoking DB::Get(). One way
+  // to make this lighter weight is to avoid doing any IOs.
+  // Default implementation here returns true and sets 'value_found' to false
+  virtual bool KeyMayExist(const ReadOptions& options,
+                           const Slice& key,
+                           std::string* value,
+                           bool* value_found = nullptr) {
+    if (value_found != nullptr) {
+      *value_found = false;
+    }
+    return true;
+  }

  // Return a heap-allocated iterator over the contents of the database.
  // The result of NewIterator() is initially invalid (caller must
@@ -153,7 +193,14 @@ class DB {
  // end==nullptr is treated as a key after all keys in the database.
  // Therefore the following call will compact the entire database:
  //    db->CompactRange(nullptr, nullptr);
-  virtual void CompactRange(const Slice* begin, const Slice* end) = 0;
+  // Note that after the entire database is compacted, all data are pushed
+  // down to the last level containing any data. If the total data size
+  // after compaction is reduced, that level might not be appropriate for
+  // hosting all the files. In this case, client could set reduce_level
+  // to true, to move the files back to the minimum level capable of holding
+  // the data set.
+  virtual void CompactRange(const Slice* begin, const Slice* end,
+                            bool reduce_level = false) = 0;

  // Number of levels used for this DB.
  virtual int NumberLevels() = 0;
@@ -185,7 +232,15 @@ class DB {
  virtual Status GetLiveFiles(std::vector<std::string>&,
                              uint64_t* manifest_file_size) = 0;

-  // The sequence number of the most recent transaction. 
+  // Retrieve the sorted list of all wal files with earliest file first
+  virtual Status GetSortedWalFiles(VectorLogPtr& files) = 0;
+
+  // Delete wal files in files. These can be either live or archived.
+  // Returns Status::OK if all files could be deleted, otherwise Status::IOError
+  // which contains information about files that could not be deleted.
+  virtual Status DeleteWalFiles(const VectorLogPtr& files) = 0;
+
+  // The sequence number of the most recent transaction.
  virtual SequenceNumber GetLatestSequenceNumber() = 0;

  // Return's an iterator for all writes since the sequence number
@@ -28,10 +28,41 @@ class RandomAccessFile;
 class SequentialFile;
 class Slice;
 class WritableFile;
+class Options;

 using std::unique_ptr;
 using std::shared_ptr;

+
+// Options while opening a file to read/write
+struct EnvOptions {
+
+  // construct with default Options
+  EnvOptions();
+
+  // construct from Options
+  EnvOptions(const Options& options);
+
+  // If true, then allow caching of data in environment buffers
+  bool use_os_buffer;
+
+   // If true, then use mmap to read data
+  bool use_mmap_reads;
+
+   // If true, then use mmap to write data
+  bool use_mmap_writes;
+
+  // If true, set the FD_CLOEXEC on open fd.
+  bool set_fd_cloexec;
+
+  // Allows OS to incrementally sync files to disk while they are being
+  // written, in the background. Issue one request for every bytes_per_sync
+  // written. 0 turns it off.
+  // Default: 0
+  uint64_t bytes_per_sync;
+
+};
+
 class Env {
 public:
  Env() { }
@@ -51,7 +82,9 @@ class Env {
  //
  // The returned file will only be accessed by one thread at a time.
  virtual Status NewSequentialFile(const std::string& fname,
-                                   unique_ptr<SequentialFile>* result) = 0;
+                                   unique_ptr<SequentialFile>* result,
+                                   const EnvOptions& options)
+                                   = 0;

  // Create a brand new random access read-only file with the
  // specified name.  On success, stores a pointer to the new file in
@@ -61,7 +94,9 @@ class Env {
  //
  // The returned file may be concurrently accessed by multiple threads.
  virtual Status NewRandomAccessFile(const std::string& fname,
-                                     unique_ptr<RandomAccessFile>* result) = 0;
+                                     unique_ptr<RandomAccessFile>* result,
+                                     const EnvOptions& options)
+                                     = 0;

  // Create an object that writes to a new file with the specified
  // name.  Deletes any existing file with the same name and creates a
@@ -71,7 +106,8 @@ class Env {
  //
  // The returned file will only be accessed by one thread at a time.
  virtual Status NewWritableFile(const std::string& fname,
-                                 unique_ptr<WritableFile>* result) = 0;
+                                 unique_ptr<WritableFile>* result,
+                                 const EnvOptions& options) = 0;

  // Returns true iff the named file exists.
  virtual bool FileExists(const std::string& fname) = 0;
@@ -228,7 +264,7 @@ class RandomAccessFile {
  // the file is opened (and will stay the same while the file is open).
  // Furthermore, it tries to make this ID at most "max_size" bytes. If such an
  // ID can be created this function returns the length of the ID and places it
-  // in "id"; otherwise, this function returns 0, in which case "id" may more
+  // in "id"; otherwise, this function returns 0, in which case "id"
  // may not have been modified.
  //
  // This function guarantees, for IDs from a given environment, two unique ids
@@ -243,6 +279,12 @@ class RandomAccessFile {
    return 0; // Default implementation to prevent issues with backwards
              // compatibility.
  };
+
+
+  enum AccessPattern { NORMAL, RANDOM, SEQUENTIAL, WILLNEED, DONTNEED };
+
+  virtual void Hint(AccessPattern pattern) {}
+
 };

 // A file abstraction for sequential writing.  The implementation
@@ -324,6 +366,16 @@ class WritableFile {
    return Status::OK();
  }

+  // Sync a file range with disk.
+  // offset is the starting byte of the file range to be synchronized.
+  // nbytes specifies the length of the range to be synchronized.
+  // This asks the OS to initiate flushing the cached data to disk,
+  // without waiting for completion.
+  // Default implementation does nothing.
+  virtual Status RangeSync(off64_t offset, off64_t nbytes) {
+    return Status::OK();
+  }
+
 private:
  size_t last_preallocated_block_;
  size_t preallocation_block_size_;
@@ -398,15 +450,18 @@ class EnvWrapper : public Env {

  // The following text is boilerplate that forwards all methods to target()
  Status NewSequentialFile(const std::string& f,
-                           unique_ptr<SequentialFile>* r) {
-    return target_->NewSequentialFile(f, r);
+                           unique_ptr<SequentialFile>* r,
+                           const EnvOptions& options) {
+    return target_->NewSequentialFile(f, r, options);
  }
  Status NewRandomAccessFile(const std::string& f,
-                             unique_ptr<RandomAccessFile>* r) {
-    return target_->NewRandomAccessFile(f, r);
+                             unique_ptr<RandomAccessFile>* r,
+                             const EnvOptions& options) {
+    return target_->NewRandomAccessFile(f, r, options);
  }
-  Status NewWritableFile(const std::string& f, unique_ptr<WritableFile>* r) {
-    return target_->NewWritableFile(f, r);
+  Status NewWritableFile(const std::string& f, unique_ptr<WritableFile>* r,
+                         const EnvOptions& options) {
+    return target_->NewWritableFile(f, r, options);
  }
  bool FileExists(const std::string& f) { return target_->FileExists(f); }
  Status GetChildren(const std::string& dir, std::vector<std::string>* r) {
@@ -0,0 +1,14 @@
+// Copyright 2008-present Facebook. All Rights Reserved.
+#ifndef STORAGE_LEVELDB_INCLUDE_LDB_TOOL_H
+#define STORAGE_LEVELDB_INCLUDE_LDB_TOOL_H
+#include "leveldb/options.h"
+
+namespace leveldb {
+
+class LDBTool {
+ public:
+  void Run(int argc, char** argv, Options = Options());
+};
+
+} // namespace leveldb
+#endif // STORAGE_LEVELDB_INCLUDE_LDB_TOOL_H
@@ -0,0 +1,88 @@
+// This file contains the interface that must be implemented by any collection
+// to be used as the backing store for a MemTable. Such a collection must
+// satisfy the following properties:
+//  (1) It does not store duplicate items.
+//  (2) It uses MemTableRep::KeyComparator to compare items for iteration and
+//     equality.
+//  (3) It can be accessed concurrently by multiple readers but need not support
+//      concurrent writes.
+//  (4) Items are never deleted.
+// The liberal use of assertions is encouraged to enforce (1).
+
+#ifndef STORAGE_LEVELDB_DB_TABLE_H_
+#define STORAGE_LEVELDB_DB_TABLE_H_
+
+#include <memory>
+#include "leveldb/arena.h"
+
+namespace leveldb {
+
+class MemTableRep {
+ public:
+  // KeyComparator(a, b) returns a negative value if a is less than b, 0 if they
+  // are equal, and a positive value if b is greater than a
+  class KeyComparator {
+  public:
+    virtual int operator()(const char* a, const char* b) const = 0;
+    virtual ~KeyComparator() { }
+  };
+
+  // Insert key into the collection. (The caller will pack key and value into a
+  // single buffer and pass that in as the parameter to Insert)
+  // REQUIRES: nothing that compares equal to key is currently in the
+  // collection.
+  virtual void Insert(const char* key) = 0;
+
+  // Returns true iff an entry that compares equal to key is in the collection.
+  virtual bool Contains(const char* key) const = 0;
+
+  virtual ~MemTableRep() { }
+
+  // Iteration over the contents of a skip collection
+  class Iterator {
+   public:
+    // Initialize an iterator over the specified collection.
+    // The returned iterator is not valid.
+    // explicit Iterator(const MemTableRep* collection);
+    virtual ~Iterator() { };
+
+    // Returns true iff the iterator is positioned at a valid node.
+    virtual bool Valid() const = 0;
+
+    // Returns the key at the current position.
+    // REQUIRES: Valid()
+    virtual const char* key() const = 0;
+
+    // Advances to the next position.
+    // REQUIRES: Valid()
+    virtual void Next() = 0;
+
+    // Advances to the previous position.
+    // REQUIRES: Valid()
+    virtual void Prev() = 0;
+
+    // Advance to the first entry with a key >= target
+    virtual void Seek(const char* target) = 0;
+
+    // Position at the first entry in collection.
+    // Final state of iterator is Valid() iff collection is not empty.
+    virtual void SeekToFirst() = 0;
+
+    // Position at the last entry in collection.
+    // Final state of iterator is Valid() iff collection is not empty.
+    virtual void SeekToLast() = 0;
+  };
+
+  virtual std::shared_ptr<Iterator> GetIterator() = 0;
+};
+
+class MemTableRepFactory {
+ public:
+  virtual ~MemTableRepFactory() { };
+  virtual std::shared_ptr<MemTableRep> CreateMemTableRep(
+    MemTableRep::KeyComparator&, Arena* arena) = 0;
+};
+
+}
+
+#endif // STORAGE_LEVELDB_DB_TABLE_H_
@@ -0,0 +1,147 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_MERGE_OPERATOR_H_
+#define STORAGE_LEVELDB_INCLUDE_MERGE_OPERATOR_H_
+
+#include <string>
+#include <deque>
+#include "leveldb/slice.h"  // TODO: Remove this when migration is done;
+
+namespace leveldb {
+
+class Slice;
+class Logger;
+
+// The Merge Operator
+//
+// Essentially, a MergeOperator specifies the SEMANTICS of a merge, which only
+// client knows. It could be numeric addition, list append, string
+// concatenation, edit data structure, ... , anything.
+// The library, on the other hand, is concerned with the exercise of this
+// interface, at the right time (during get, iteration, compaction...)
+//
+// To use merge, the client needs to provide an object implementing one of
+// the following interfaces:
+//  a) AssociativeMergeOperator - for most simple semantics (always take
+//    two values, and merge them into one value, which is then put back
+//    into rocksdb); numeric addition and string concatenation are examples;
+//
+//  b) MergeOperator - the generic class for all the more abstract / complex
+//    operations; one method (FullMerge) to merge a Put/Delete value with a
+//    merge operand; and another method (PartialMerge) that merges two
+//    operands together. this is especially useful if your key values have a
+//    complex structure but you would still like to support client-specific
+//    incremental updates.
+//
+// AssociativeMergeOperator is simpler to implement. MergeOperator is simply
+// more powerful.
+//
+// Refer to rocksdb-merge wiki for more details and example implementations.
+//
+class MergeOperator {
+ public:
+  virtual ~MergeOperator() {}
+
+  // Gives the client a way to express the read -> modify -> write semantics
+  // key:      (IN)    The key that's associated with this merge operation.
+  //                   Client could multiplex the merge operator based on it
+  //                   if the key space is partitioned and different subspaces
+  //                   refer to different types of data which have different
+  //                   merge operation semantics
+  // existing: (IN)    null indicates that the key does not exist before this op
+  // operand_list:(IN) the sequence of merge operations to apply, front() first.
+  // new_value:(OUT)   Client is responsible for filling the merge result here
+  // logger:   (IN)    Client could use this to log errors during merge.
+  //
+  // Return true on success.
+  // All values passed in will be client-specific values. So if this method
+  // returns false, it is because client specified bad data or there was
+  // internal corruption. This will be treated as an error by the library.
+  //
+  // Also make use of the *logger for error messages.
+  virtual bool FullMerge(const Slice& key,
+                         const Slice* existing_value,
+                         const std::deque<std::string>& operand_list,
+                         std::string* new_value,
+                         Logger* logger) const = 0;
+
+  // This function performs merge(left_op, right_op)
+  // when both the operands are themselves merge operation types
+  // that you would have passed to a DB::Merge() call in the same order
+  // (i.e.: DB::Merge(key,left_op), followed by DB::Merge(key,right_op)).
+  //
+  // PartialMerge should combine them into a single merge operation that is
+  // saved into *new_value, and then it should return true.
+  // *new_value should be constructed such that a call to
+  // DB::Merge(key, *new_value) would yield the same result as a call
+  // to DB::Merge(key, left_op) followed by DB::Merge(key, right_op).
+  //
+  // If it is impossible or infeasible to combine the two operations,
+  // leave new_value unchanged and return false. The library will
+  // internally keep track of the operations, and apply them in the
+  // correct order once a base-value (a Put/Delete/End-of-Database) is seen.
+  //
+  // TODO: Presently there is no way to differentiate between error/corruption
+  // and simply "return false". For now, the client should simply return
+  // false in any case it cannot perform partial-merge, regardless of reason.
+  // If there is corruption in the data, handle it in the FullMerge() function,
+  // and return false there.
+  virtual bool PartialMerge(const Slice& key,
+                            const Slice& left_operand,
+                            const Slice& right_operand,
+                            std::string* new_value,
+                            Logger* logger) const = 0;
+
+  // The name of the MergeOperator. Used to check for MergeOperator
+  // mismatches (i.e., a DB created with one MergeOperator is
+  // accessed using a different MergeOperator)
+  // TODO: the name is currently not stored persistently and thus
+  //       no checking is enforced. Client is responsible for providing
+  //       consistent MergeOperator between DB opens.
+  virtual const char* Name() const = 0;
+};
+
+// The simpler, associative merge operator.
+class AssociativeMergeOperator : public MergeOperator {
+ public:
+  virtual ~AssociativeMergeOperator() {}
+
+  // Gives the client a way to express the read -> modify -> write semantics
+  // key:           (IN) The key that's associated with this merge operation.
+  // existing_value:(IN) null indicates the key does not exist before this op
+  // value:         (IN) the value to update/merge the existing_value with
+  // new_value:    (OUT) Client is responsible for filling the merge result here
+  // logger:        (IN) Client could use this to log errors during merge.
+  //
+  // Return true on success.
+  // All values passed in will be client-specific values. So if this method
+  // returns false, it is because client specified bad data or there was
+  // internal corruption. The client should assume that this will be treated
+  // as an error by the library.
+  virtual bool Merge(const Slice& key,
+                     const Slice* existing_value,
+                     const Slice& value,
+                     std::string* new_value,
+                     Logger* logger) const = 0;
+
+
+ private:
+  // Default implementations of the MergeOperator functions
+  virtual bool FullMerge(const Slice& key,
+                         const Slice* existing_value,
+                         const std::deque<std::string>& operand_list,
+                         std::string* new_value,
+                         Logger* logger) const override;
+
+  virtual bool PartialMerge(const Slice& key,
+                            const Slice& left_operand,
+                            const Slice& right_operand,
+                            std::string* new_value,
+                            Logger* logger) const override;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_MERGE_OPERATOR_H_
@@ -11,6 +11,11 @@
 #include <vector>
 #include <stdint.h>
 #include "leveldb/slice.h"
+#include "leveldb/statistics.h"
+#include "leveldb/universal_compaction.h"
+#include "leveldb/memtablerep.h"
+
+#include "leveldb/slice_transform.h"

 namespace leveldb {

@@ -19,8 +24,10 @@ class Comparator;
 class Env;
 class FilterPolicy;
 class Logger;
+class MergeOperator;
 class Snapshot;
-class Statistics;
+class CompactionFilter;
+class CompactionFilterFactory;

 using std::shared_ptr;

@@ -37,6 +44,11 @@ enum CompressionType {
  kBZip2Compression = 0x3
 };

+enum CompactionStyle {
+  kCompactionStyleLevel       = 0x0, // level based compaction style
+  kCompactionStyleUniversal   = 0x1  // Universal compaction style
+};
+
 // Compression options for different compression algorithms like Zlib
 struct CompressionOptions {
  int window_bits;
@@ -63,6 +75,28 @@ struct Options {
  // comparator provided to previous open calls on the same DB.
  const Comparator* comparator;

+  // REQUIRES: The client must provide a merge operator if Merge operation
+  // needs to be accessed. Calling Merge on a DB without a merge operator
+  // would result in Status::NotSupported. The client must ensure that the
+  // merge operator supplied here has the same name and *exactly* the same
+  // semantics as the merge operator provided to previous open calls on
+  // the same DB. The only exception is reserved for upgrade, where a DB
+  // previously without a merge operator is introduced to Merge operation
+  // for the first time. It's necessary to specify a merge operator when
+  // openning the DB in this case.
+  // Default: nullptr
+  shared_ptr<MergeOperator> merge_operator;
+
+  // The client must provide compaction_filter_factory if it requires a new
+  // compaction filter to be used for different compaction processes
+  // Allows an application to modify/delete a key-value during background
+  // compaction.
+  // Ideally, client should specify only one of filter or factory.
+  // compaction_filter takes precedence over compaction_filter_factory if
+  // client specifies both.
+  // Default: nullptr
+  const CompactionFilter* compaction_filter;
+
  // If true, the database will be created if it is missing.
  // Default: false
  bool create_if_missing;
@@ -112,6 +146,15 @@ struct Options {
  // Default: 2
  int max_write_buffer_number;

+  // The minimum number of write buffers that will be merged together
+  // before writing to storage.  If set to 1, then
+  // all write buffers are fushed to L0 as individual files and this increases
+  // read amplification because a get request has to check in all of these
+  // files. Also, an in-memory merge may result in writing lesser
+  // data to storage if there are duplicate records in each of these
+  // individual write buffers.  Default: 1
+  int min_write_buffer_number_to_merge;
+
  // Number of open files that can be used by the DB.  You may need to
  // increase this if your database has a large working set (budget
  // one open file per 2MB of working set).
@@ -183,6 +226,28 @@ struct Options {
  // Default: nullptr
  const FilterPolicy* filter_policy;

+  // If non-nullptr, use the specified function to determine the
+  // prefixes for keys.  These prefixes will be placed in the filter.
+  // Depending on the workload, this can reduce the number of read-IOP
+  // cost for scans when a prefix is passed via ReadOptions to
+  // db.NewIterator().  For prefix filtering to work properly,
+  // "prefix_extractor" and "comparator" must be such that the following
+  // properties hold:
+  //
+  // 1) key.starts_with(prefix(key))
+  // 2) Compare(prefix(key), key) <= 0.
+  // 3) If Compare(k1, k2) <= 0, then Compare(prefix(k1), prefix(k2)) <= 0
+  // 4) prefix(prefix(key)) == prefix(key)
+  //
+  // Default: nullptr
+  const SliceTransform* prefix_extractor;
+
+  // If true, place whole keys in the filter (not just prefixes).
+  // This must generally be true for gets to be efficient.
+  //
+  // Default: true
+  bool whole_key_filtering;
+
  // Number of levels for this database
  int num_levels;

@@ -190,9 +255,9 @@ struct Options {
  // level-0 compaction will not be triggered by number of files at all.
  int level0_file_num_compaction_trigger;

-  // Soft limit on number of level-0 files. We slow down writes at this point.
-  // A value <0 means that no writing slow down will be triggered by number
-  // of files in level-0.
+  // Soft limit on number of level-0 files. We start slowing down writes at this
+  // point. A value <0 means that no writing slow down will be triggered by
+  // number of files in level-0.
  int level0_slowdown_writes_trigger;

  // Maximum number of level-0 files.  We stop writes at this point.
@@ -236,6 +301,12 @@ struct Options {
  // by default 'max_bytes_for_level_base' is 10.
  int max_bytes_for_level_multiplier;

+  // Different max-size multipliers for different levels.
+  // These are multiplied by max_bytes_for_level_multiplier to arrive
+  // at the max-size of each level.
+  // Default: 1
+  std::vector<int> max_bytes_for_level_multiplier_additional;
+
  // Maximum number of bytes in all compacted files.  We avoid expanding
  // the lower level file set of a compaction if it would make the
  // total compaction cover more than
@@ -258,7 +329,7 @@ struct Options {
  // If non-null, then we should collect metrics about database operations
  // Statistics objects should not be shared between DB instances as
  // it does not use any locks to prevent concurrent updates.
-  Statistics* statistics;
+  shared_ptr<Statistics> statistics;

  // If true, then the contents of data files are not synced
  // to stable storage. Their contents remain in the OS buffers till the
@@ -320,26 +391,44 @@ struct Options {
  // Default: 1000
  size_t keep_log_file_num;

-  // Puts are delayed when any level has a compaction score that
-  // exceeds rate_limit. This is ignored when <= 1.0.
-  double rate_limit;
+  // Puts are delayed 0-1 ms when any level has a compaction score that exceeds
+  // soft_rate_limit. This is ignored when == 0.0.
+  // CONSTRAINT: soft_rate_limit <= hard_rate_limit. If this constraint does not
+  // hold, RocksDB will set soft_rate_limit = hard_rate_limit
+  // Default: 0 (disabled)
+  double soft_rate_limit;

-  // Max time a put will be stalled when rate_limit is enforced
-  int rate_limit_delay_milliseconds;
+  // Puts are delayed 1ms at a time when any level has a compaction score that
+  // exceeds hard_rate_limit. This is ignored when <= 1.0.
+  // Default: 0 (disabled)
+  double hard_rate_limit;
+
+  // Max time a put will be stalled when hard_rate_limit is enforced. If 0, then
+  // there is no limit.
+  // Default: 1000
+  unsigned int rate_limit_delay_max_milliseconds;

  // manifest file is rolled over on reaching this limit.
  // The older manifest file be deleted.
  // The default value is MAX_INT so that roll-over does not take place.
  uint64_t max_manifest_file_size;

-  // Disable block cache. If this is set to false,
+  // Disable block cache. If this is set to true,
  // then no block cache should be used, and the block_cache should
  // point to a nullptr object.
+  // Default: false
  bool no_block_cache;

  // Number of shards used for table cache.
  int table_cache_numshardbits;

+  // size of one block in arena memory allocation.
+  // If <= 0, a proper value is automatically calculated (usually 1/10 of
+  // writer_buffer_size).
+  //
+  // Default: 0
+  size_t arena_block_size;
+
  // Create an Options object with default values for all fields.
  Options();

@@ -354,25 +443,6 @@ struct Options {
  // from the database, because otherwise the read can be very slow.
  Options* PrepareForBulkLoad();

-  // This method allows an application to modify/delete a key-value at
-  // the time of compaction. The compaction process invokes this
-  // method for every kv that is being compacted. A return value
-  // of false indicates that the kv should be preserved in the
-  // output of this compaction run and a return value of true
-  // indicates that this key-value should be removed from the
-  // output of the compaction.  The application can inspect
-  // the existing value of the key, modify it if needed and
-  // return back the new value for this key. The application
-  // should allocate memory for the Slice object that is used to
-  // return the new value and the leveldb framework will
-  // free up that memory.
-  // The compaction_filter_args, if specified here, are passed
-  // back to the invocation of the CompactionFilter.
-  void* compaction_filter_args;
-  bool (*CompactionFilter)(void* compaction_filter_args,
-         int level, const Slice& key,
-         const Slice& existing_value, Slice** new_value);
-
  // Disable automatic compactions. Manual compactions can still
  // be issued on this database.
  bool disable_auto_compactions;
@@ -396,6 +466,82 @@ struct Options {
  // Purge duplicate/deleted keys when a memtable is flushed to storage.
  // Default: true
  bool purge_redundant_kvs_while_flush;
+
+  // Data being read from file storage may be buffered in the OS
+  // Default: true
+  bool allow_os_buffer;
+
+  // Allow the OS to mmap file for reading sst tables. Default: false
+  bool allow_mmap_reads;
+
+  // Allow the OS to mmap file for writing. Default: true
+  bool allow_mmap_writes;
+
+  // Disable child process inherit open files. Default: true
+  bool is_fd_close_on_exec;
+
+  // Skip log corruption error on recovery (If client is ok with
+  // losing most recent changes)
+  // Default: false
+  bool skip_log_error_on_recovery;
+
+  // if not zero, dump leveldb.stats to LOG every stats_dump_period_sec
+  // Default: 3600 (1 hour)
+  unsigned int stats_dump_period_sec;
+
+  // This is used to close a block before it reaches the configured
+  // 'block_size'. If the percentage of free space in the current block is less
+  // than this specified number and adding a new record to the block will
+  // exceed the configured block size, then this block will be closed and the
+  // new record will be written to the next block.
+  // Default is 10.
+  int block_size_deviation;
+
+  // If set true, will hint the underlying file system that the file
+  // access pattern is random, when a sst file is opened.
+  // Default: true
+  bool advise_random_on_open;
+
+  // Specify the file access pattern once a compaction is started.
+  // It will be applied to all input files of a compaction.
+  // Default: NORMAL
+  enum { NONE, NORMAL, SEQUENTIAL, WILLNEED } access_hint_on_compaction_start;
+
+  // Use adaptive mutex, which spins in the user space before resorting
+  // to kernel. This could reduce context switch when the mutex is not
+  // heavily contended. However, if the mutex is hot, we could end up
+  // wasting spin time.
+  // Default: false
+  bool use_adaptive_mutex;
+
+  // Allows OS to incrementally sync files to disk while they are being
+  // written, asynchronously, in the background.
+  // Issue one request for every bytes_per_sync written. 0 turns it off.
+  // Default: 0
+  uint64_t bytes_per_sync;
+
+  // The compaction style. Default: kCompactionStyleLevel
+  CompactionStyle compaction_style;
+
+  // The options needed to support Universal Style compactions
+  CompactionOptionsUniversal compaction_options_universal;
+
+  // Use KeyMayExist API to filter deletes when this is true.
+  // If KeyMayExist returns false, i.e. the key definitely does not exist, then
+  // the delete is a noop. KeyMayExist only incurs in-memory look up.
+  // This optimization avoids writing the delete to storage when appropriate.
+  // Default: false
+  bool filter_deletes;
+
+  // This is a factory that provides MemTableRep objects.
+  // Default: a factory that provides a skip-list-based implementation of
+  // MemTableRep.
+  std::shared_ptr<MemTableRepFactory> memtable_factory;
+
+  // This is a factory that provides compaction filter objects which allow
+  // an application to modify/delete a key-value during background compaction.
+  // Default: a factory that doesn't provide any object
+  std::shared_ptr<CompactionFilterFactory> compaction_filter_factory;
 };

 // Options that control read operations
@@ -417,14 +563,28 @@ struct ReadOptions {
  // Default: nullptr
  const Snapshot* snapshot;

+  // If "prefix" is non-nullptr, and ReadOptions is being passed to
+  // db.NewIterator, only return results when the key begins with this
+  // prefix.  This field is ignored by other calls (e.g., Get).
+  // Options.prefix_extractor must also be set, and
+  // prefix_extractor.InRange(prefix) must be true.  The iterator
+  // returned by NewIterator when this option is set will behave just
+  // as if the underlying store did not contain any non-matching keys,
+  // with two exceptions.  Seek() only accepts keys starting with the
+  // prefix, and SeekToLast() is not supported.  prefix filter with this
+  // option will sometimes reduce the number of read IOPs.
+  // Default: nullptr
+  const Slice* prefix;
+
  ReadOptions()
      : verify_checksums(false),
        fill_cache(true),
-        snapshot(nullptr) {
+        snapshot(nullptr),
+        prefix(nullptr) {
  }
  ReadOptions(bool cksum, bool cache) :
              verify_checksums(cksum), fill_cache(cache),
-              snapshot(nullptr) {
+              snapshot(nullptr), prefix(nullptr) {
  }
 };

@@ -0,0 +1,24 @@
+#ifndef STORAGE_LEVELDB_INCLUDE_PERF_CONTEXT_H
+#define STORAGE_LEVELDB_INCLUDE_PERF_CONTEXT_H
+
+#include <stdint.h>
+
+namespace leveldb {
+
+// A thread local context for gathering performance counter efficiently
+// and transparently.
+
+struct PerfContext {
+
+  void Reset(); // reset all performance counters to zero
+
+
+  uint64_t user_key_comparison_count; // total number of user key comparisons
+};
+
+extern __thread PerfContext perf_context;
+
+}
+
+
+#endif
@@ -0,0 +1,41 @@
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// Class for specifying user-defined functions which perform a
+// transformation on a slice.  It is not required that every slice
+// belong to the domain and/or range of a function.  Subclasses should
+// define InDomain and InRange to determine which slices are in either
+// of these sets respectively.
+
+#ifndef STORAGE_LEVELDB_INCLUDE_SLICE_TRANSFORM_H_
+#define STORAGE_LEVELDB_INCLUDE_SLICE_TRANSFORM_H_
+
+#include <string>
+
+namespace leveldb {
+
+class Slice;
+
+class SliceTransform {
+ public:
+  virtual ~SliceTransform() {};
+
+  // Return the name of this transformation.
+  virtual const char* Name() const = 0;
+
+  // transform a src in domain to a dst in the range
+  virtual Slice Transform(const Slice& src) const = 0;
+
+  // determine whether this is a valid src upon the function applies
+  virtual bool InDomain(const Slice& src) const = 0;
+
+  // determine whether dst=Transform(src) for some src
+  virtual bool InRange(const Slice& dst) const = 0;
+};
+
+extern const SliceTransform* NewFixedPrefixTransform(size_t prefix_len);
+
+}
+
+#endif  // STORAGE_LEVELDB_INCLUDE_SLICE_TRANSFORM_H_
@@ -5,10 +5,13 @@
 #ifndef STORAGE_LEVELDB_INCLUDE_STATISTICS_H_
 #define STORAGE_LEVELDB_INCLUDE_STATISTICS_H_

+#include <atomic>
+#include <cassert>
 #include <cstddef>
 #include <cstdint>
 #include <string>
 #include <memory>
+#include <vector>

 namespace leveldb {

@@ -16,6 +19,7 @@ namespace leveldb {
 * Keep adding ticker's here.
 * Any ticker should have a value less than TICKER_ENUM_MAX.
 * Add a new ticker by assigning it the current value of TICKER_ENUM_MAX
+ * Add a string representation in TickersNameMap below.
 * And incrementing TICKER_ENUM_MAX.
 */
 enum Tickers {
@@ -39,21 +43,105 @@ enum Tickers {
  NO_FILE_CLOSES = 10,
  NO_FILE_OPENS = 11,
  NO_FILE_ERRORS = 12,
-  TICKER_ENUM_MAX = 13,
+  // Time system had to wait to do LO-L1 compactions
+  STALL_L0_SLOWDOWN_MICROS = 13,
+  // Time system had to wait to move memtable to L1.
+  STALL_MEMTABLE_COMPACTION_MICROS = 14,
+  // write throttle because of too many files in L0
+  STALL_L0_NUM_FILES_MICROS = 15,
+  RATE_LIMIT_DELAY_MILLIS = 16,
+
+  NO_ITERATORS = 17, // number of iterators currently open
+
+  // Number of MultiGet calls, keys read, and bytes read
+  NUMBER_MULTIGET_CALLS = 18,
+  NUMBER_MULTIGET_KEYS_READ = 19,
+  NUMBER_MULTIGET_BYTES_READ = 20,
+
+  NUMBER_FILTERED_DELETES = 21,
+  NUMBER_MERGE_FAILURES = 22,
+  SEQUENCE_NUMBER = 23,
+
+  TICKER_ENUM_MAX = 24
 };

+const std::vector<std::pair<Tickers, std::string>> TickersNameMap = {
+  { BLOCK_CACHE_MISS, "rocksdb.block.cache.miss" },
+  { BLOCK_CACHE_HIT, "rocksdb.block.cache.hit" },
+  { BLOOM_FILTER_USEFUL, "rocksdb.bloom.filter.useful" },
+  { COMPACTION_KEY_DROP_NEWER_ENTRY, "rocksdb.compaction.key.drop.new" },
+  { COMPACTION_KEY_DROP_OBSOLETE, "rocksdb.compaction.key.drop.obsolete" },
+  { COMPACTION_KEY_DROP_USER, "rocksdb.compaction.key.drop.user" },
+  { NUMBER_KEYS_WRITTEN, "rocksdb.number.keys.written" },
+  { NUMBER_KEYS_READ, "rocksdb.number.keys.read" },
+  { BYTES_WRITTEN, "rocksdb.bytes.written" },
+  { BYTES_READ, "rocksdb.bytes.read" },
+  { NO_FILE_CLOSES, "rocksdb.no.file.closes" },
+  { NO_FILE_OPENS, "rocksdb.no.file.opens" },
+  { NO_FILE_ERRORS, "rocksdb.no.file.errors" },
+  { STALL_L0_SLOWDOWN_MICROS, "rocksdb.l0.slowdown.micros" },
+  { STALL_MEMTABLE_COMPACTION_MICROS, "rocksdb.memtable.compaction.micros" },
+  { STALL_L0_NUM_FILES_MICROS, "rocksdb.l0.num.files.stall.micros" },
+  { RATE_LIMIT_DELAY_MILLIS, "rocksdb.rate.limit.delay.millis" },
+  { NO_ITERATORS, "rocksdb.num.iterators" },
+  { NUMBER_MULTIGET_CALLS, "rocksdb.number.multiget.get" },
+  { NUMBER_MULTIGET_KEYS_READ, "rocksdb.number.multiget.keys.read" },
+  { NUMBER_MULTIGET_BYTES_READ, "rocksdb.number.multiget.bytes.read" },
+  { NUMBER_FILTERED_DELETES, "rocksdb.number.deletes.filtered" },
+  { NUMBER_MERGE_FAILURES, "rocksdb.number.merge.failures" },
+  { SEQUENCE_NUMBER, "rocksdb.sequence.number" }
+};

 /**
 * Keep adding histogram's here.
 * Any histogram whould have value less than HISTOGRAM_ENUM_MAX
 * Add a new Histogram by assigning it the current value of HISTOGRAM_ENUM_MAX
+ * Add a string representation in HistogramsNameMap below
 * And increment HISTOGRAM_ENUM_MAX
 */
 enum Histograms {
  DB_GET = 0,
  DB_WRITE = 1,
  COMPACTION_TIME = 2,
-  HISTOGRAM_ENUM_MAX = 3,
+  TABLE_SYNC_MICROS = 3,
+  COMPACTION_OUTFILE_SYNC_MICROS = 4,
+  WAL_FILE_SYNC_MICROS = 5,
+  MANIFEST_FILE_SYNC_MICROS = 6,
+  // TIME SPENT IN IO DURING TABLE OPEN
+  TABLE_OPEN_IO_MICROS = 7,
+  DB_MULTIGET = 8,
+  READ_BLOCK_COMPACTION_MICROS = 9,
+  READ_BLOCK_GET_MICROS = 10,
+  WRITE_RAW_BLOCK_MICROS = 11,
+
+  STALL_L0_SLOWDOWN_COUNT = 12,
+  STALL_MEMTABLE_COMPACTION_COUNT = 13,
+  STALL_L0_NUM_FILES_COUNT = 14,
+  HARD_RATE_LIMIT_DELAY_COUNT = 15,
+  SOFT_RATE_LIMIT_DELAY_COUNT = 16,
+  NUM_FILES_IN_SINGLE_COMPACTION = 17,
+  HISTOGRAM_ENUM_MAX = 18
+};
+
+const std::vector<std::pair<Histograms, std::string>> HistogramsNameMap = {
+  { DB_GET, "rocksdb.db.get.micros" },
+  { DB_WRITE, "rocksdb.db.write.micros" },
+  { COMPACTION_TIME, "rocksdb.compaction.times.micros" },
+  { TABLE_SYNC_MICROS, "rocksdb.table.sync.micros" },
+  { COMPACTION_OUTFILE_SYNC_MICROS, "rocksdb.compaction.outfile.sync.micros" },
+  { WAL_FILE_SYNC_MICROS, "rocksdb.wal.file.sync.micros" },
+  { MANIFEST_FILE_SYNC_MICROS, "rocksdb.manifest.file.sync.micros" },
+  { TABLE_OPEN_IO_MICROS, "rocksdb.table.open.io.micros" },
+  { DB_MULTIGET, "rocksdb.db.multiget.micros" },
+  { READ_BLOCK_COMPACTION_MICROS, "rocksdb.read.block.compaction.micros" },
+  { READ_BLOCK_GET_MICROS, "rocksdb.read.block.get.micros" },
+  { WRITE_RAW_BLOCK_MICROS, "rocksdb.write.raw.block.micros" },
+  { STALL_L0_SLOWDOWN_COUNT, "rocksdb.l0.slowdown.count"},
+  { STALL_MEMTABLE_COMPACTION_COUNT, "rocksdb.memtable.compaction.count"},
+  { STALL_L0_NUM_FILES_COUNT, "rocksdb.num.files.stall.count"},
+  { HARD_RATE_LIMIT_DELAY_COUNT, "rocksdb.hard.rate.limit.delay.count"},
+  { SOFT_RATE_LIMIT_DELAY_COUNT, "rocksdb.soft.rate.limit.delay.count"},
+  { NUM_FILES_IN_SINGLE_COMPACTION, "rocksdb.numfiles.in.singlecompaction" }
 };

 struct HistogramData {
@@ -72,7 +160,6 @@ class Histogram {
  virtual ~Histogram();
  // Add a value to be recorded in the histogram.
  virtual void Add(uint64_t value) = 0;
-  virtual void Add(double value) = 0;

  virtual std::string ToString() const = 0;

@@ -93,11 +180,11 @@ class Ticker {
 public:
  Ticker() : count_(0) { }

-  inline void recordTick() {
-    count_++;
+  inline void setTickerCount(uint64_t count) {
+    count_ = count;
  }

-  inline void recordTick(int count) {
+  inline void recordTick(int count = 1) {
    count_ += count;
  }

@@ -106,8 +193,7 @@ class Ticker {
  }

 private:
-  uint64_t count_;
-
+  std::atomic_uint_fast64_t count_;
 };

 // Analyze the performance of a db
@@ -116,21 +202,38 @@ class Statistics {

  virtual long getTickerCount(Tickers tickerType) = 0;
  virtual void recordTick(Tickers tickerType, uint64_t count = 0) = 0;
-  virtual void measureTime(Histograms histogramType, uint64_t count) = 0;
-  virtual void measureTime(Histograms histogramType, double count) = 0;
+  virtual void setTickerCount(Tickers tickerType, uint64_t count) = 0;
+  virtual void measureTime(Histograms histogramType, uint64_t time) = 0;

  virtual void histogramData(Histograms type, HistogramData * const data) = 0;
-
+  // String representation of the statistic object.
+  std::string ToString();
 };

+// Create a concrete DBStatistics object
+std::shared_ptr<Statistics> CreateDBStatistics();
+
 // Ease of Use functions
-inline void RecordTick(Statistics* const statistics,
+inline void RecordTick(std::shared_ptr<Statistics> statistics,
                       Tickers ticker,
                       uint64_t count = 1) {
-  if (statistics != nullptr) {
+  assert(HistogramsNameMap.size() == HISTOGRAM_ENUM_MAX);
+  assert(TickersNameMap.size() == TICKER_ENUM_MAX);
+  if (statistics) {
    statistics->recordTick(ticker, count);
  }
 }
+
+inline void SetTickerCount(std::shared_ptr<Statistics> statistics,
+                           Tickers ticker,
+                           uint64_t count) {
+  assert(HistogramsNameMap.size() == HISTOGRAM_ENUM_MAX);
+  assert(TickersNameMap.size() == TICKER_ENUM_MAX);
+  if (statistics) {
+    statistics->setTickerCount(ticker, count);
+  }
+}
+
 }  // namespace leveldb

 #endif  // STORAGE_LEVELDB_INCLUDE_STATISTICS_H_
@@ -47,6 +47,9 @@ class Status {
  static Status IOError(const Slice& msg, const Slice& msg2 = Slice()) {
    return Status(kIOError, msg, msg2);
  }
+  static Status MergeInProgress(const Slice& msg, const Slice& msg2 = Slice()) {
+    return Status(kMergeInProgress, msg, msg2);
+  }

  // Returns true iff the status indicates success.
  bool ok() const { return (state_ == nullptr); }
@@ -66,6 +69,9 @@ class Status {
  // Returns true iff the status indicates an IOError.
  bool IsIOError() const { return code() == kIOError; }

+  // Returns true iff the status indicates an MergeInProgress.
+  bool IsMergeInProgress() const { return code() == kMergeInProgress; }
+
  // Return a string representation of this status suitable for printing.
  // Returns the string "OK" for success.
  std::string ToString() const;
@@ -84,7 +90,8 @@ class Status {
    kCorruption = 2,
    kNotSupported = 3,
    kInvalidArgument = 4,
-    kIOError = 5
+    kIOError = 5,
+    kMergeInProgress = 6
  };

  Code code() const {
@@ -3,10 +3,46 @@
 #define STORAGE_LEVELDB_INCLUDE_TRANSACTION_LOG_ITERATOR_H_

 #include "leveldb/status.h"
+#include "leveldb/types.h"
 #include "leveldb/write_batch.h"

 namespace leveldb {

+class LogFile;
+typedef std::vector<std::unique_ptr<LogFile>> VectorLogPtr;
+
+enum  WalFileType {
+  /* Indicates that WAL file is in archive directory. WAL files are moved from
+   * the main db directory to archive directory once they are not live and stay
+   * there for a duration of WAL_ttl_seconds which can be set in Options
+   */
+  kArchivedLogFile = 0,
+
+  /* Indicates that WAL file is live and resides in the main db directory */
+  kAliveLogFile = 1
+} ;
+
+class LogFile {
+ public:
+  LogFile() {}
+  virtual ~LogFile() {}
+
+  // Returns log file's name excluding the db path
+  virtual std::string Filename() const = 0;
+
+  // Primary identifier for log file.
+  // This is directly proportional to creation time of the log file
+  virtual uint64_t LogNumber() const = 0;
+
+  // Log file can be either alive or archived
+  virtual WalFileType Type() const = 0;
+
+  // Starting sequence number of writebatch written in this log file
+  virtual SequenceNumber StartSequence() const = 0;
+
+  // Size of log file on disk in Bytes
+  virtual uint64_t SizeFileBytes() const = 0;
+};

 struct BatchResult {
  SequenceNumber sequence;
@@ -7,7 +7,7 @@ namespace leveldb {

 // Define all public custom types here.

-//  Represents a sequence number in a WAL file.
+// Represents a sequence number in a WAL file.
 typedef uint64_t SequenceNumber;

 }  //  namespace leveldb
@@ -0,0 +1,57 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_ROCKSDB_UNIVERSAL_COMPACTION_OPTIONS_H
+#define STORAGE_ROCKSDB_UNIVERSAL_COMPACTION_OPTIONS_H
+
+#include <stddef.h>
+#include <string>
+#include <memory>
+#include <vector>
+#include <stdint.h>
+#include <climits>
+#include "leveldb/slice.h"
+#include "leveldb/statistics.h"
+
+namespace leveldb {
+
+//
+// Algorithm used to make a compaction request stop picking new files
+// into a single compaction run
+//
+enum CompactionStopStyle {
+  kCompactionStopStyleSimilarSize, // pick files of similar size
+  kCompactionStopStyleTotalSize    // total size of picked files > next file
+};
+
+class CompactionOptionsUniversal {
+ public:
+
+  // Percentage flexibilty while comparing file size. If the candidate file(s)
+  // size is 1% smaller than the next file's size, then include next file into
+  // this candidate set. // Default: 1
+  unsigned int size_ratio;
+
+  // The minimum number of files in a single compaction run. Default: 2
+  unsigned int min_merge_width;
+
+  // The maximum number of files in a single compaction run. Default: INT_MAX
+  unsigned int max_merge_width;
+
+  // The algorithm used to stop picking files into a single compaction run
+  // Default: kCompactionStopStyleTotalSize
+  CompactionStopStyle stop_style;
+
+  // Default set of parameters
+  CompactionOptionsUniversal() :
+    size_ratio(1),
+    min_merge_width(2),
+    max_merge_width(UINT_MAX),
+    stop_style(kCompactionStopStyleTotalSize) {
+  }
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_ROCKSDB_UNIVERSAL_COMPACTION_OPTIONS_H
@@ -36,9 +36,24 @@ class WriteBatch {
  // Store the mapping "key->value" in the database.
  void Put(const Slice& key, const Slice& value);

+  // Merge "value" with the existing value of "key" in the database.
+  // "key->merge(existing, value)"
+  void Merge(const Slice& key, const Slice& value);
+
  // If the database contains a mapping for "key", erase it.  Else do nothing.
  void Delete(const Slice& key);

+  // Append a blob of arbitrary to the records in this batch. The blob will be
+  // stored in the transaction log but not in any other file. In particular, it
+  // will not be persisted to the SST files. When iterating over this
+  // WriteBatch, WriteBatch::Handler::LogData will be called with the contents
+  // of the blob as it is encountered. Blobs, puts, deletes, and merges will be
+  // encountered in the same order in thich they were inserted.
+  //
+  // Example application: add timestamps to the transaction log for use in
+  // replication.
+  void PutLogData(const Slice& blob);
+
  // Clear all updates buffered in this batch.
  void Clear();

@@ -47,15 +62,24 @@ class WriteBatch {
   public:
    virtual ~Handler();
    virtual void Put(const Slice& key, const Slice& value) = 0;
+    // Merge and LogData are not pure virtual. Otherwise, we would break
+    // existing clients of Handler on a source code level. The default
+    // implementation of Merge simply throws a runtime exception.
+    virtual void Merge(const Slice& key, const Slice& value);
+    // The default implementation of LogData does nothing.
+    virtual void LogData(const Slice& blob);
    virtual void Delete(const Slice& key) = 0;
  };
  Status Iterate(Handler* handler) const;

-  // Retrive the serialized version of this batch.
+  // Retrieve the serialized version of this batch.
  std::string Data() { return rep_; }

+  // Returns the number of updates in the batch
+  int Count() const;
+
  // Constructor with a serialized string object
-  WriteBatch(std::string rep): rep_(rep) {}
+  explicit WriteBatch(std::string rep): rep_(rep) {}

 private:
  friend class WriteBatchInternal;
@@ -0,0 +1,163 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef LEVELDB_INCLUDE_UTILITIES_STACKABLE_DB_H_
+#define LEVELDB_INCLUDE_UTILITIES_STACKABLE_DB_H_
+
+#include "leveldb/db.h"
+
+namespace leveldb {
+
+// This class contains APIs to stack rocksdb wrappers.Eg. Stack TTL over base d
+class StackableDB : public DB {
+ public:
+  explicit StackableDB(StackableDB* sdb) : sdb_(sdb) {}
+
+  // Returns the DB object that is the lowermost component in the stack of DBs
+  virtual DB* GetRawDB() {
+    return sdb_->GetRawDB();
+  }
+
+  // convert a DB to StackableDB
+  static StackableDB* DBToStackableDB(DB* db) {
+    class NewStackableDB : public StackableDB {
+     public:
+      NewStackableDB(DB* db)
+        : StackableDB(nullptr),
+          db_(db) {}
+
+      DB* GetRawDB() {
+        return db_;
+      }
+
+     private:
+      DB* db_;
+    };
+    return new NewStackableDB(db);
+  }
+
+  virtual Status Put(const WriteOptions& options,
+                     const Slice& key,
+                     const Slice& val) override {
+    return sdb_->Put(options, key, val);
+  }
+
+  virtual Status Get(const ReadOptions& options,
+                     const Slice& key,
+                     std::string* value) override {
+    return sdb_->Get(options, key, value);
+  }
+
+  virtual std::vector<Status> MultiGet(const ReadOptions& options,
+                                       const std::vector<Slice>& keys,
+                                       std::vector<std::string>* values)
+    override {
+      return sdb_->MultiGet(options, keys, values);
+  }
+
+  virtual bool KeyMayExist(const ReadOptions& options,
+                           const Slice& key,
+                           std::string* value,
+                           bool* value_found = nullptr) override {
+    return sdb_->KeyMayExist(options, key, value, value_found);
+  }
+
+  virtual Status Delete(const WriteOptions& wopts, const Slice& key) override {
+    return sdb_->Delete(wopts, key);
+  }
+
+  virtual Status Merge(const WriteOptions& options,
+                       const Slice& key,
+                       const Slice& value) override {
+    return sdb_->Merge(options, key, value);
+  }
+
+
+  virtual Status Write(const WriteOptions& opts, WriteBatch* updates)
+    override {
+      return sdb_->Write(opts, updates);
+  }
+
+  virtual Iterator* NewIterator(const ReadOptions& opts) override {
+    return sdb_->NewIterator(opts);
+  }
+
+  virtual const Snapshot* GetSnapshot() override {
+    return sdb_->GetSnapshot();
+  }
+
+  virtual void ReleaseSnapshot(const Snapshot* snapshot) override {
+    return sdb_->ReleaseSnapshot(snapshot);
+  }
+
+  virtual bool GetProperty(const Slice& property, std::string* value)
+    override {
+      return sdb_->GetProperty(property, value);
+  }
+
+  virtual void GetApproximateSizes(const Range* r, int n, uint64_t* sizes)
+    override {
+      return sdb_->GetApproximateSizes(r, n, sizes);
+  }
+
+  virtual void CompactRange(const Slice* begin, const Slice* end,
+                            bool reduce_level = false) override {
+    return sdb_->CompactRange(begin, end, reduce_level);
+  }
+
+  virtual int NumberLevels() override {
+    return sdb_->NumberLevels();
+  }
+
+  virtual int MaxMemCompactionLevel() override {
+    return sdb_->MaxMemCompactionLevel();
+  }
+
+  virtual int Level0StopWriteTrigger() override {
+    return sdb_->Level0StopWriteTrigger();
+  }
+
+  virtual Status Flush(const FlushOptions& fopts) override {
+    return sdb_->Flush(fopts);
+  }
+
+  virtual Status DisableFileDeletions() override {
+    return sdb_->DisableFileDeletions();
+  }
+
+  virtual Status EnableFileDeletions() override {
+    return sdb_->EnableFileDeletions();
+  }
+
+  virtual Status GetLiveFiles(std::vector<std::string>& vec, uint64_t* mfs)
+    override {
+      return sdb_->GetLiveFiles(vec, mfs);
+  }
+
+  virtual SequenceNumber GetLatestSequenceNumber() override {
+    return sdb_->GetLatestSequenceNumber();
+  }
+
+  virtual Status GetSortedWalFiles(VectorLogPtr& files) override {
+    return sdb_->GetSortedWalFiles(files);
+  }
+
+  virtual Status DeleteWalFiles(const VectorLogPtr& files)
+    override{
+      return sdb_->DeleteWalFiles(files);
+  }
+
+  virtual Status GetUpdatesSince(SequenceNumber seq_number,
+                                 unique_ptr<TransactionLogIterator>* iter)
+    override {
+      return sdb_->GetUpdatesSince(seq_number, iter);
+  }
+
+ protected:
+  StackableDB* sdb_;
+};
+
+} //  namespace leveldb
+
+#endif  //  LEVELDB_INCLUDE_UTILITIES_STACKABLE_DB_H_
@@ -0,0 +1,54 @@
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef LEVELDB_INCLUDE_UTILITIES_UTILITY_DB_H_
+#define LEVELDB_INCLUDE_UTILITIES_UTILITY_DB_H_
+
+#include "stackable_db.h"
+
+namespace leveldb {
+
+// This class contains APIs to open leveldb with specific support eg. TTL
+class UtilityDB {
+
+  public:
+    // Open the database with TTL support.
+    //
+    // USE-CASES:
+    // This API should be used to open the db when key-values inserted are
+    //  meant to be removed from the db in a non-strict 'ttl' amount of time
+    //  Therefore, this guarantees that key-values inserted will remain in the
+    //  db for >= ttl amount of time and the db will make efforts to remove the
+    //  key-values as soon as possible after ttl seconds of their insertion.
+    //
+    // BEHAVIOUR:
+    // TTL is accepted in seconds
+    // (int32_t)Timestamp(creation) is suffixed to values in Put internally
+    // Expired TTL values deleted in compaction only:(Timestamp+ttl<time_now)
+    // Get/Iterator may return expired entries(compaction not run on them yet)
+    // Different TTL may be used during different Opens
+    // Example: Open1 at t=0 with ttl=4 and insert k1,k2, close at t=2
+    //          Open2 at t=3 with ttl=5. Now k1,k2 should be deleted at t>=5
+    // read_only=true opens in the usual read-only mode. Compactions will not be
+    //  triggered(neither manual nor automatic), so no expired entries removed
+    //
+    // CONSTRAINTS:
+    // Not specifying/passing or non-positive TTL behaves like TTL = infinity
+    //
+    // !!!WARNING!!!:
+    // Calling DB::Open directly to re-open a db created by this API will get
+    //  corrupt values(timestamp suffixed) and no ttl effect will be there
+    //  during the second Open, so use this API consistently to open the db
+    // Be careful when passing ttl with a small positive value because the
+    //  whole database may be deleted in a small amount of time
+    static Status OpenTtlDB(const Options& options,
+                            const std::string& name,
+                            StackableDB** dbptr,
+                            int32_t ttl = 0,
+                            bool read_only = false);
+};
+
+} //  namespace leveldb
+
+#endif  //  LEVELDB_INCLUDE_UTILITIES_UTILITY_DB_H_
@@ -19,7 +19,24 @@ static void PthreadCall(const char* label, int result) {
  }
 }

-Mutex::Mutex() { PthreadCall("init mutex", pthread_mutex_init(&mu_, NULL)); }
+Mutex::Mutex(bool adaptive) {
+#ifdef OS_LINUX
+  if (!adaptive) {
+    PthreadCall("init mutex", pthread_mutex_init(&mu_, NULL));
+  } else {
+    pthread_mutexattr_t mutex_attr;
+    PthreadCall("init mutex attr", pthread_mutexattr_init(&mutex_attr));
+    PthreadCall("set mutex attr",
+                pthread_mutexattr_settype(&mutex_attr,
+                                          PTHREAD_MUTEX_ADAPTIVE_NP));
+    PthreadCall("init mutex", pthread_mutex_init(&mu_, &mutex_attr));
+    PthreadCall("destroy mutex attr",
+                pthread_mutexattr_destroy(&mutex_attr));
+  }
+#else // ignore adaptive for non-linux platform
+  PthreadCall("init mutex", pthread_mutex_init(&mu_, NULL));
+#endif // OS_LINUX
+}

 Mutex::~Mutex() { PthreadCall("destroy mutex", pthread_mutex_destroy(&mu_)); }

@@ -82,7 +82,7 @@ class CondVar;

 class Mutex {
 public:
-  Mutex();
+  /* implicit */ Mutex(bool adaptive = false);
  ~Mutex();

  void Lock();
@@ -192,17 +192,20 @@ inline bool Zlib_Compress(const CompressionOptions& opts, const char* input,
  _stream.avail_out = length;
  _stream.next_out = (Bytef *)&(*output)[0];

-  int old_sz =0, new_sz =0;
-  while(_stream.next_in != NULL && _stream.avail_in != 0) {
+  int old_sz =0, new_sz =0, new_sz_delta =0;
+  bool done = false;
+  while (!done) {
    int st = deflate(&_stream, Z_FINISH);
    switch (st) {
      case Z_STREAM_END:
+        done = true;
        break;
      case Z_OK:
        // No output space. Increase the output space by 20%.
        // (Should we fail the compression since it expands the size?)
        old_sz = output->size();
-        new_sz = (int)(output->size() * 1.2);
+        new_sz_delta = (int)(output->size() * 0.2);
+        new_sz = output->size() + (new_sz_delta < 10 ? 10 : new_sz_delta);
        output->resize(new_sz);
        // Set more output.
        _stream.next_out = (Bytef *)&(*output)[old_sz];
@@ -228,13 +231,13 @@ inline char* Zlib_Uncompress(const char* input_data, size_t input_length,
  z_stream _stream;
  memset(&_stream, 0, sizeof(z_stream));

-  // For raw inflate, the windowBits should be Ð8..Ð15.
+  // For raw inflate, the windowBits should be -8..-15.
  // If windowBits is bigger than zero, it will use either zlib
  // header or gzip header. Adding 32 to it will do automatic detection.
  int st = inflateInit2(&_stream,
      windowBits > 0 ? windowBits + 32 : windowBits);
  if (st != Z_OK) {
-    return NULL;
+    return nullptr;
  }

  _stream.next_in = (Bytef *)input_data;
@@ -248,17 +251,22 @@ inline char* Zlib_Uncompress(const char* input_data, size_t input_length,
  _stream.next_out = (Bytef *)output;
  _stream.avail_out = output_len;

-  char* tmp = NULL;
+  char* tmp = nullptr;
+  int output_len_delta;
+  bool done = false;

-  while(_stream.next_in != NULL && _stream.avail_in != 0) {
+  //while(_stream.next_in != nullptr && _stream.avail_in != 0) {
+  while (!done) {
    int st = inflate(&_stream, Z_SYNC_FLUSH);
    switch (st) {
      case Z_STREAM_END:
+        done = true;
        break;
      case Z_OK:
        // No output space. Increase the output space by 20%.
        old_sz = output_len;
-        output_len = (int)(output_len * 1.2);
+        output_len_delta = (int)(output_len * 0.2);
+        output_len += output_len_delta < 10 ? 10 : output_len_delta;
        tmp = new char[output_len];
        memcpy(tmp, output, old_sz);
        delete[] output;
@@ -272,7 +280,7 @@ inline char* Zlib_Uncompress(const char* input_data, size_t input_length,
      default:
        delete[] output;
        inflateEnd(&_stream);
-        return NULL;
+        return nullptr;
    }
  }

@@ -281,7 +289,7 @@ inline char* Zlib_Uncompress(const char* input_data, size_t input_length,
  return output;
 #endif

-  return NULL;
+  return nullptr;
 }

 inline bool BZip2_Compress(const CompressionOptions& opts, const char* input,
@@ -311,7 +319,7 @@ inline bool BZip2_Compress(const CompressionOptions& opts, const char* input,
  _stream.avail_out = length;

  int old_sz =0, new_sz =0;
-  while(_stream.next_in != NULL && _stream.avail_in != 0) {
+  while(_stream.next_in != nullptr && _stream.avail_in != 0) {
    int st = BZ2_bzCompress(&_stream, BZ_FINISH);
    switch (st) {
      case BZ_STREAM_END:
@@ -349,7 +357,7 @@ inline char*  BZip2_Uncompress(const char* input_data, size_t input_length,

  int st = BZ2_bzDecompressInit(&_stream, 0, 0);
  if (st != BZ_OK) {
-    return NULL;
+    return nullptr;
  }

  _stream.next_in = (char *)input_data;
@@ -363,9 +371,9 @@ inline char*  BZip2_Uncompress(const char* input_data, size_t input_length,
  _stream.next_out = (char *)output;
  _stream.avail_out = output_len;

-  char* tmp = NULL;
+  char* tmp = nullptr;

-  while(_stream.next_in != NULL && _stream.avail_in != 0) {
+  while(_stream.next_in != nullptr && _stream.avail_in != 0) {
    int st = BZ2_bzDecompress(&_stream);
    switch (st) {
      case BZ_STREAM_END:
@@ -387,7 +395,7 @@ inline char*  BZip2_Uncompress(const char* input_data, size_t input_length,
      default:
        delete[] output;
        BZ2_bzDecompressEnd(&_stream);
-        return NULL;
+        return nullptr;
    }
  }

@@ -395,7 +403,7 @@ inline char*  BZip2_Uncompress(const char* input_data, size_t input_length,
  BZ2_bzDecompressEnd(&_stream);
  return output;
 #endif
-  return NULL;
+  return nullptr;
 }

 inline bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg) {
@@ -0,0 +1,97 @@
+#include "util/stack_trace.h"
+
+#ifdef OS_LINUX
+
+#include <execinfo.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+namespace leveldb {
+
+static const char* GetExecutableName()
+{
+  static char name[1024];
+
+  char link[1024];
+  snprintf(link, sizeof(link), "/proc/%d/exe", getpid());
+  auto read = readlink(link, name, sizeof(name));
+  if (-1 == read) {
+    return nullptr;
+  } else {
+    name[read] = 0;
+    return name;
+  }
+}
+
+static void StackTraceHandler(int sig) {
+  // reset to default handler
+  signal(sig, SIG_DFL);
+
+  fprintf(stderr, "Received signal %d (%s)\n", sig, strsignal(sig));
+
+  const int kMaxFrames = 100;
+  void *frames[kMaxFrames];
+
+  auto num_frames = backtrace(frames, kMaxFrames);
+  auto symbols = backtrace_symbols(frames, num_frames);
+
+  auto executable = GetExecutableName();
+
+  const int kSkip = 2; // skip the top two signal handler related frames
+
+  for (int i = kSkip; i < num_frames; ++i)
+  {
+    fprintf(stderr, "#%-2d %p ", i - kSkip, frames[i]);
+    if (symbols) {
+      fprintf(stderr, "%s ", symbols[i]);
+    }
+    if (executable) {
+      // out source to addr2line, for the address translation
+      const int kLineMax = 256;
+      char cmd[kLineMax];
+      sprintf(cmd,"addr2line %p -e %s 2>&1", frames[i] , executable);
+      auto f = popen(cmd, "r");
+      if (f) {
+        char line[kLineMax];
+        while (fgets(line, sizeof(line), f)) {
+          fprintf(stderr, "%s", line);
+        }
+        pclose(f);
+      } else {
+        fprintf(stderr, "\n");
+      }
+    } else {
+      fprintf(stderr, "\n");
+    }
+  }
+
+  // re-signal to default handler (so we still get core dump if needed...)
+  raise(sig);
+}
+
+void InstallStackTraceHandler() {
+  // just use the plain old signal as it's simple and sufficient
+  // for this use case
+  signal(SIGILL, StackTraceHandler);
+  signal(SIGSEGV, StackTraceHandler);
+  signal(SIGBUS, StackTraceHandler);
+  signal(SIGABRT, StackTraceHandler);
+
+  printf("Installed stack trace handler for SIGILL SIGSEGV SIGBUS SIGABRT\n");
+
+}
+
+}   // namespace leveldb
+
+#else // no-op for non-linux system for now
+
+namespace leveldb {
+
+void InstallStackTraceHandler() {}
+
+}
+
+#endif // OS_LINUX
@@ -23,7 +23,8 @@ inline uint32_t Block::NumRestarts() const {
 Block::Block(const BlockContents& contents)
    : data_(contents.data.data()),
      size_(contents.data.size()),
-      owned_(contents.heap_allocated) {
+      owned_(contents.heap_allocated),
+      cachable_(contents.cachable) {
  if (size_ < sizeof(uint32_t)) {
    size_ = 0;  // Error marker
  } else {
@@ -22,6 +22,7 @@ class Block {
  ~Block();

  size_t size() const { return size_; }
+  bool   isCachable() const { return cachable_; }
  Iterator* NewIterator(const Comparator* comparator);

 private:
@@ -31,6 +32,7 @@ class Block {
  size_t size_;
  uint32_t restart_offset_;     // Offset in data_ of restart array
  bool owned_;                  // Block owns data_[]
+  bool cachable_;

  // No copying allowed
  Block(const Block&);
@@ -60,6 +60,21 @@ size_t BlockBuilder::CurrentSizeEstimate() const {
          sizeof(uint32_t));                      // Restart array length
 }

+size_t BlockBuilder::EstimateSizeAfterKV(const Slice& key, const Slice& value)
+  const {
+  size_t estimate = CurrentSizeEstimate();
+  estimate += key.size() + value.size();
+  if (counter_ >= options_->block_restart_interval) {
+    estimate += sizeof(uint32_t); // a new restart entry.
+  }
+
+  estimate += sizeof(int32_t); // varint for shared prefix length.
+  estimate += VarintLength(key.size()); // varint for key length.
+  estimate += VarintLength(value.size()); // varint for value length.
+
+  return estimate;
+}
+
 Slice BlockBuilder::Finish() {
  // Append restart array
  for (size_t i = 0; i < restarts_.size(); i++) {
@@ -34,6 +34,9 @@ class BlockBuilder {
  // we are building.
  size_t CurrentSizeEstimate() const;

+  // Returns an estimated block size after appending key and value.
+  size_t EstimateSizeAfterKV(const Slice& key, const Slice& value) const;
+
  // Return true iff no entries have been added since the last Reset()
  bool empty() const {
    return buffer_.empty();
@@ -1,9 +1,6 @@
 // Copyright (c) 2012 Facebook.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.
-
-#include "leveldb/table.h"
-
 #include <string>
 #include "db/dbformat.h"
 #include "db/memtable.h"
@@ -14,6 +11,7 @@
 #include "leveldb/table_builder.h"
 #include "table/block.h"
 #include "table/block_builder.h"
+#include "table/table.h"
 #include "table/format.h"
 #include "util/random.h"
 #include "util/testharness.h"
@@ -60,7 +58,7 @@ TEST(BlockTest, SimpleTest) {
  // read serialized contents of the block
  Slice rawblock = builder.Finish();

-  // create block reader 
+  // create block reader
  BlockContents contents;
  contents.data = rawblock;
  contents.cachable = false;
@@ -71,7 +69,7 @@ TEST(BlockTest, SimpleTest) {
  int count = 0;
  Iterator* iter = reader.NewIterator(options.comparator);
  for (iter->SeekToFirst();iter->Valid(); count++, iter->Next()) {
-    
+
    // read kv from block
    Slice k = iter->key();
    Slice v = iter->value();
@@ -81,8 +79,8 @@ TEST(BlockTest, SimpleTest) {
    ASSERT_EQ(v.ToString().compare(values[count]), 0);
  }
  delete iter;
-  
-  // read block contents randomly 
+
+  // read block contents randomly
  iter = reader.NewIterator(options.comparator);
  for (int i = 0; i < num_records; i++) {

@@ -4,6 +4,7 @@

 #include "table/filter_block.h"

+#include "db/dbformat.h"
 #include "leveldb/filter_policy.h"
 #include "util/coding.h"

@@ -15,9 +16,11 @@ namespace leveldb {
 static const size_t kFilterBaseLg = 11;
 static const size_t kFilterBase = 1 << kFilterBaseLg;

-FilterBlockBuilder::FilterBlockBuilder(const FilterPolicy* policy)
-    : policy_(policy) {
-}
+FilterBlockBuilder::FilterBlockBuilder(const Options& opt)
+                 : policy_(opt.filter_policy),
+                   prefix_extractor_(opt.prefix_extractor),
+                   whole_key_filtering_(opt.whole_key_filtering),
+                   comparator_(opt.comparator){}

 void FilterBlockBuilder::StartBlock(uint64_t block_offset) {
  uint64_t filter_index = (block_offset / kFilterBase);
@@ -27,10 +30,47 @@ void FilterBlockBuilder::StartBlock(uint64_t block_offset) {
  }
 }

+bool FilterBlockBuilder::SamePrefix(const Slice &key1,
+                                    const Slice &key2) const {
+  if (!prefix_extractor_->InDomain(key1) &&
+      !prefix_extractor_->InDomain(key2)) {
+    return true;
+  } else if (!prefix_extractor_->InDomain(key1) ||
+             !prefix_extractor_->InDomain(key2)) {
+    return false;
+  } else {
+    return (prefix_extractor_->Transform(key1) ==
+            prefix_extractor_->Transform(key2));
+  }
+}
+
 void FilterBlockBuilder::AddKey(const Slice& key) {
-  Slice k = key;
-  start_.push_back(keys_.size());
-  keys_.append(k.data(), k.size());
+  Slice prev;
+  if (start_.size() > 0) {
+    size_t prev_start = start_[start_.size() - 1];
+    const char* base = entries_.data() + prev_start;
+    size_t length = entries_.size() - prev_start;
+    prev = Slice(base, length);
+  }
+
+  if (whole_key_filtering_) {
+    start_.push_back(entries_.size());
+    entries_.append(key.data(), key.size());
+  }
+
+  if (prefix_extractor_ && prefix_extractor_->InDomain(key)) {
+    // this assumes prefix(prefix(key)) == prefix(key), as the last
+    // entry in entries_ may be either a key or prefix, and we use
+    // prefix(last entry) to get the prefix of the last key.
+    if (prev.size() == 0 || ! SamePrefix(key, prev)) {
+      Slice prefix = prefix_extractor_->Transform(key);
+      InternalKey internal_prefix_tmp(prefix, 0, kTypeValue);
+      Slice internal_prefix = internal_prefix_tmp.Encode();
+      assert(comparator_->Compare(internal_prefix, key) <= 0);
+      start_.push_back(entries_.size());
+      entries_.append(internal_prefix.data(), internal_prefix.size());
+    }
+  }
 }

 Slice FilterBlockBuilder::Finish() {
@@ -50,34 +90,35 @@ Slice FilterBlockBuilder::Finish() {
 }

 void FilterBlockBuilder::GenerateFilter() {
-  const size_t num_keys = start_.size();
-  if (num_keys == 0) {
+  const size_t num_entries = start_.size();
+  if (num_entries == 0) {
    // Fast path if there are no keys for this filter
    filter_offsets_.push_back(result_.size());
    return;
  }

  // Make list of keys from flattened key structure
-  start_.push_back(keys_.size());  // Simplify length computation
-  tmp_keys_.resize(num_keys);
-  for (size_t i = 0; i < num_keys; i++) {
-    const char* base = keys_.data() + start_[i];
+  start_.push_back(entries_.size());  // Simplify length computation
+  tmp_entries_.resize(num_entries);
+  for (size_t i = 0; i < num_entries; i++) {
+    const char* base = entries_.data() + start_[i];
    size_t length = start_[i+1] - start_[i];
-    tmp_keys_[i] = Slice(base, length);
+    tmp_entries_[i] = Slice(base, length);
  }

  // Generate filter for current set of keys and append to result_.
  filter_offsets_.push_back(result_.size());
-  policy_->CreateFilter(&tmp_keys_[0], num_keys, &result_);
+  policy_->CreateFilter(&tmp_entries_[0], num_entries, &result_);

-  tmp_keys_.clear();
-  keys_.clear();
+  tmp_entries_.clear();
+  entries_.clear();
  start_.clear();
 }

-FilterBlockReader::FilterBlockReader(const FilterPolicy* policy,
-                                     const Slice& contents)
-    : policy_(policy),
+FilterBlockReader::FilterBlockReader(const Options& opt, const Slice& contents)
+    : policy_(opt.filter_policy),
+      prefix_extractor_(opt.prefix_extractor),
+      whole_key_filtering_(opt.whole_key_filtering),
      data_(nullptr),
      offset_(nullptr),
      num_(0),
@@ -92,16 +133,32 @@ FilterBlockReader::FilterBlockReader(const FilterPolicy* policy,
  num_ = (n - 5 - last_word) / 4;
 }

-bool FilterBlockReader::KeyMayMatch(uint64_t block_offset, const Slice& key) {
+bool FilterBlockReader::KeyMayMatch(uint64_t block_offset,
+                                    const Slice& key) {
+  if (!whole_key_filtering_) {
+    return true;
+  }
+  return MayMatch(block_offset, key);
+}
+
+bool FilterBlockReader::PrefixMayMatch(uint64_t block_offset,
+                                       const Slice& prefix) {
+  if (!prefix_extractor_) {
+    return true;
+  }
+  return MayMatch(block_offset, prefix);
+}
+
+bool FilterBlockReader::MayMatch(uint64_t block_offset, const Slice& entry) {
  uint64_t index = block_offset >> base_lg_;
  if (index < num_) {
    uint32_t start = DecodeFixed32(offset_ + index*4);
    uint32_t limit = DecodeFixed32(offset_ + index*4 + 4);
    if (start <= limit && limit <= (offset_ - data_)) {
      Slice filter = Slice(data_ + start, limit - start);
-      return policy_->KeyMayMatch(key, filter);
+      return policy_->KeyMayMatch(entry, filter);
    } else if (start == limit) {
-      // Empty filters do not match any keys
+      // Empty filters do not match any entries
      return false;
    }
  }
@@ -13,7 +13,9 @@
 #include <stdint.h>
 #include <string>
 #include <vector>
+#include "leveldb/options.h"
 #include "leveldb/slice.h"
+#include "leveldb/slice_transform.h"
 #include "util/hash.h"

 namespace leveldb {
@@ -28,20 +30,25 @@ class FilterPolicy;
 //      (StartBlock AddKey*)* Finish
 class FilterBlockBuilder {
 public:
-  explicit FilterBlockBuilder(const FilterPolicy*);
+  explicit FilterBlockBuilder(const Options& opt);

  void StartBlock(uint64_t block_offset);
  void AddKey(const Slice& key);
  Slice Finish();

 private:
+  bool SamePrefix(const Slice &key1, const Slice &key2) const;
  void GenerateFilter();

  const FilterPolicy* policy_;
-  std::string keys_;              // Flattened key contents
-  std::vector<size_t> start_;     // Starting index in keys_ of each key
-  std::string result_;            // Filter data computed so far
-  std::vector<Slice> tmp_keys_;   // policy_->CreateFilter() argument
+  const SliceTransform* prefix_extractor_;
+  bool whole_key_filtering_;
+  const Comparator* comparator_;
+
+  std::string entries_;         // Flattened entry contents
+  std::vector<size_t> start_;   // Starting index in entries_ of each entry
+  std::string result_;          // Filter data computed so far
+  std::vector<Slice> tmp_entries_; // policy_->CreateFilter() argument
  std::vector<uint32_t> filter_offsets_;

  // No copying allowed
@@ -52,15 +59,20 @@ class FilterBlockBuilder {
 class FilterBlockReader {
 public:
 // REQUIRES: "contents" and *policy must stay live while *this is live.
-  FilterBlockReader(const FilterPolicy* policy, const Slice& contents);
+  FilterBlockReader(const Options& opt, const Slice& contents);
  bool KeyMayMatch(uint64_t block_offset, const Slice& key);
+  bool PrefixMayMatch(uint64_t block_offset, const Slice& prefix);

 private:
  const FilterPolicy* policy_;
+  const SliceTransform* prefix_extractor_;
+  bool whole_key_filtering_;
  const char* data_;    // Pointer to filter data (at block-start)
  const char* offset_;  // Pointer to beginning of offset array (at block-end)
  size_t num_;          // Number of entries in offset array
  size_t base_lg_;      // Encoding parameter (see kFilterBaseLg in .cc file)
+
+  bool MayMatch(uint64_t block_offset, const Slice& entry);
 };

 }
@@ -41,19 +41,25 @@ class TestHashFilter : public FilterPolicy {
 class FilterBlockTest {
 public:
  TestHashFilter policy_;
+  Options options_;
+
+  FilterBlockTest() {
+    options_ = Options();
+    options_.filter_policy = &policy_;
+  }
 };

 TEST(FilterBlockTest, EmptyBuilder) {
-  FilterBlockBuilder builder(&policy_);
+  FilterBlockBuilder builder(options_);
  Slice block = builder.Finish();
  ASSERT_EQ("\\x00\\x00\\x00\\x00\\x0b", EscapeString(block));
-  FilterBlockReader reader(&policy_, block);
+  FilterBlockReader reader(options_, block);
  ASSERT_TRUE(reader.KeyMayMatch(0, "foo"));
  ASSERT_TRUE(reader.KeyMayMatch(100000, "foo"));
 }

 TEST(FilterBlockTest, SingleChunk) {
-  FilterBlockBuilder builder(&policy_);
+  FilterBlockBuilder builder(options_);
  builder.StartBlock(100);
  builder.AddKey("foo");
  builder.AddKey("bar");
@@ -63,7 +69,7 @@ TEST(FilterBlockTest, SingleChunk) {
  builder.StartBlock(300);
  builder.AddKey("hello");
  Slice block = builder.Finish();
-  FilterBlockReader reader(&policy_, block);
+  FilterBlockReader reader(options_, block);
  ASSERT_TRUE(reader.KeyMayMatch(100, "foo"));
  ASSERT_TRUE(reader.KeyMayMatch(100, "bar"));
  ASSERT_TRUE(reader.KeyMayMatch(100, "box"));
@@ -74,7 +80,7 @@ TEST(FilterBlockTest, SingleChunk) {
 }

 TEST(FilterBlockTest, MultiChunk) {
-  FilterBlockBuilder builder(&policy_);
+  FilterBlockBuilder builder(options_);

  // First filter
  builder.StartBlock(0);
@@ -94,7 +100,7 @@ TEST(FilterBlockTest, MultiChunk) {
  builder.AddKey("hello");

  Slice block = builder.Finish();
-  FilterBlockReader reader(&policy_, block);
+  FilterBlockReader reader(options_, block);

  // Check first filter
  ASSERT_TRUE(reader.KeyMayMatch(0, "foo"));
@@ -66,10 +66,10 @@ Status Footer::DecodeFrom(Slice* input) {
  return result;
 }

-Status ReadBlock(RandomAccessFile* file,
-                 const ReadOptions& options,
-                 const BlockHandle& handle,
-                 BlockContents* result) {
+Status ReadBlockContents(RandomAccessFile* file,
+                         const ReadOptions& options,
+                         const BlockHandle& handle,
+                         BlockContents* result) {
  result->data = Slice();
  result->cachable = false;
  result->heap_allocated = false;
@@ -91,10 +91,10 @@ struct BlockContents {

 // Read the block identified by "handle" from "file".  On failure
 // return non-OK.  On success fill *result and return OK.
-extern Status ReadBlock(RandomAccessFile* file,
-                        const ReadOptions& options,
-                        const BlockHandle& handle,
-                        BlockContents* result);
+extern Status ReadBlockContents(RandomAccessFile* file,
+                                const ReadOptions& options,
+                                const BlockHandle& handle,
+                                BlockContents* result);

 // Implementation details follow.  Clients should ignore,

@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.

-#include "leveldb/table.h"
+#include "table/table.h"
+
+#include "db/dbformat.h"

 #include "leveldb/cache.h"
 #include "leveldb/comparator.h"
@@ -10,11 +12,14 @@
 #include "leveldb/filter_policy.h"
 #include "leveldb/options.h"
 #include "leveldb/statistics.h"
+
 #include "table/block.h"
 #include "table/filter_block.h"
 #include "table/format.h"
 #include "table/two_level_iterator.h"
+
 #include "util/coding.h"
+#include "util/stop_watch.h"

 namespace leveldb {

@@ -29,8 +34,12 @@ struct Table::Rep {
    delete [] filter_data;
    delete index_block;
  }
+  Rep(const EnvOptions& storage_options) :
+    soptions(storage_options) {
+  }

  Options options;
+  const EnvOptions& soptions;
  Status status;
  unique_ptr<RandomAccessFile> file;
  char cache_key_prefix[kMaxCacheKeyPrefixSize];
@@ -61,7 +70,34 @@ void Table::SetupCacheKeyPrefix(Rep* rep) {
  }
 }

+namespace {  // anonymous namespace, not visible externally
+
+// Read the block identified by "handle" from "file".
+// The only relevant option is options.verify_checksums for now.
+// Set *didIO to true if didIO is not null.
+// On failure return non-OK.
+// On success fill *result and return OK - caller owns *result
+Status ReadBlock(RandomAccessFile* file,
+                 const ReadOptions& options,
+                 const BlockHandle& handle,
+                 Block** result,
+                 bool* didIO = nullptr) {
+  BlockContents contents;
+  Status s = ReadBlockContents(file, options, handle, &contents);
+  if (s.ok()) {
+    *result = new Block(contents);
+  }
+
+  if (didIO) {
+    *didIO = true;
+  }
+  return s;
+}
+
+} // end of anonymous namespace
+
 Status Table::Open(const Options& options,
+                   const EnvOptions& soptions,
                   unique_ptr<RandomAccessFile>&& file,
                   uint64_t size,
                   unique_ptr<Table>* table) {
@@ -87,20 +123,14 @@ Status Table::Open(const Options& options,
  s = footer.DecodeFrom(&footer_input);
  if (!s.ok()) return s;

-  // Read the index block
-  BlockContents contents;
  Block* index_block = nullptr;
-  if (s.ok()) {
-    s = ReadBlock(file.get(), ReadOptions(), footer.index_handle(), &contents);
-    if (s.ok()) {
-      index_block = new Block(contents);
-    }
-  }
+  // TODO: we never really verify check sum for index block
+  s = ReadBlock(file.get(), ReadOptions(), footer.index_handle(), &index_block);

  if (s.ok()) {
    // We've successfully read the footer and the index block: we're
    // ready to serve requests.
-    Rep* rep = new Table::Rep;
+    Rep* rep = new Table::Rep(soptions);
    rep->options = options;
    rep->file = std::move(file);
    rep->metaindex_handle = footer.metaindex_handle();
@@ -117,6 +147,25 @@ Status Table::Open(const Options& options,
  return s;
 }

+void Table::SetupForCompaction() {
+  switch (rep_->options.access_hint_on_compaction_start) {
+    case Options::NONE:
+      break;
+    case Options::NORMAL:
+      rep_->file->Hint(RandomAccessFile::NORMAL);
+      break;
+    case Options::SEQUENTIAL:
+      rep_->file->Hint(RandomAccessFile::SEQUENTIAL);
+      break;
+    case Options::WILLNEED:
+      rep_->file->Hint(RandomAccessFile::WILLNEED);
+      break;
+    default:
+      assert(false);
+  }
+  compaction_optimized_ = true;
+}
+
 void Table::ReadMeta(const Footer& footer) {
  if (rep_->options.filter_policy == nullptr) {
    return;  // Do not need any metadata
@@ -124,14 +173,13 @@ void Table::ReadMeta(const Footer& footer) {

  // TODO(sanjay): Skip this if footer.metaindex_handle() size indicates
  // it is an empty block.
-  ReadOptions opt;
-  BlockContents contents;
-  if (!ReadBlock(rep_->file.get(), opt, footer.metaindex_handle(),
-                 &contents).ok()) {
+  //  TODO: we never really verify check sum for meta index block
+  Block* meta = nullptr;
+  if (!ReadBlock(rep_->file.get(), ReadOptions(), footer.metaindex_handle(),
+                 &meta).ok()) {
    // Do not propagate errors since meta info is not needed for operation
    return;
  }
-  Block* meta = new Block(contents);

  Iterator* iter = meta->NewIterator(BytewiseComparator());
  std::string key = "filter.";
@@ -151,17 +199,17 @@ void Table::ReadFilter(const Slice& filter_handle_value) {
    return;
  }

-  // We might want to unify with ReadBlock() if we start
+  // TODO: We might want to unify with ReadBlock() if we start
  // requiring checksum verification in Table::Open.
  ReadOptions opt;
  BlockContents block;
-  if (!ReadBlock(rep_->file.get(), opt, filter_handle, &block).ok()) {
+  if (!ReadBlockContents(rep_->file.get(), opt, filter_handle, &block).ok()) {
    return;
  }
  if (block.heap_allocated) {
    rep_->filter_data = block.data.data();     // Will need to delete later
  }
-  rep_->filter = new FilterBlockReader(rep_->options.filter_policy, block.data);
+  rep_->filter = new FilterBlockReader(rep_->options, block.data);
 }

 Table::~Table() {
@@ -188,10 +236,12 @@ static void ReleaseBlock(void* arg, void* h) {
 Iterator* Table::BlockReader(void* arg,
                             const ReadOptions& options,
                             const Slice& index_value,
-                             bool* didIO) {
+                             bool* didIO,
+                             bool for_compaction,
+                             const bool no_io) {
  Table* table = reinterpret_cast<Table*>(arg);
  Cache* block_cache = table->rep_->options.block_cache.get();
-  Statistics* const statistics = table->rep_->options.statistics;
+  std::shared_ptr<Statistics> statistics = table->rep_->options.statistics;
  Block* block = nullptr;
  Cache::Handle* cache_handle = nullptr;

@@ -202,7 +252,6 @@ Iterator* Table::BlockReader(void* arg,
  // can add more features in the future.

  if (s.ok()) {
-    BlockContents contents;
    if (block_cache != nullptr) {
      char cache_key[kMaxCacheKeyPrefixSize + kMaxVarint64Length];
      const size_t cache_key_prefix_size = table->rep_->cache_key_prefix_size;
@@ -218,29 +267,34 @@ Iterator* Table::BlockReader(void* arg,
        block = reinterpret_cast<Block*>(block_cache->Value(cache_handle));

        RecordTick(statistics, BLOCK_CACHE_HIT);
+      } else if (no_io) {
+        return nullptr; // Did not find in block_cache and can't do IO
      } else {
-        s = ReadBlock(table->rep_->file.get(), options, handle, &contents);
-        if (s.ok()) {
-          block = new Block(contents);
-          if (contents.cachable && options.fill_cache) {
-            cache_handle = block_cache->Insert(
-                key, block, block->size(), &DeleteCachedBlock);
-          }
+        Histograms histogram = for_compaction ?
+          READ_BLOCK_COMPACTION_MICROS : READ_BLOCK_GET_MICROS;
+        {  // block for stop watch
+          StopWatch sw(table->rep_->options.env, statistics, histogram);
+          s = ReadBlock(
+                table->rep_->file.get(),
+                options,
+                handle,
+                &block,
+                didIO
+              );
        }
-        if (didIO != nullptr) {
-          *didIO = true; // we did some io from storage
+        if (s.ok()) {
+          if (block->isCachable() && options.fill_cache) {
+            cache_handle = block_cache->Insert(
+              key, block, block->size(), &DeleteCachedBlock);
+          }
        }

        RecordTick(statistics, BLOCK_CACHE_MISS);
      }
-    } else {
-      s = ReadBlock(table->rep_->file.get(), options, handle, &contents);
-      if (s.ok()) {
-        block = new Block(contents);
-      }
-      if (didIO != nullptr) {
-        *didIO = true; // we did some io from storage
-      }
+    } else if (no_io) {
+      return nullptr; // Could not read from block_cache and can't do IO
+    }else {
+      s = ReadBlock(table->rep_->file.get(), options, handle, &block, didIO);
    }
  }

@@ -260,23 +314,87 @@ Iterator* Table::BlockReader(void* arg,

 Iterator* Table::BlockReader(void* arg,
                             const ReadOptions& options,
-                             const Slice& index_value) {
-  return BlockReader(arg, options, index_value, nullptr);
+                             const EnvOptions& soptions,
+                             const Slice& index_value,
+                             bool for_compaction) {
+  return BlockReader(arg, options, index_value, nullptr, for_compaction);
+}
+
+// This will be broken if the user specifies an unusual implementation
+// of Options.comparator, or if the user specifies an unusual
+// definition of prefixes in Options.filter_policy.  In particular, we
+// require the following three properties:
+//
+// 1) key.starts_with(prefix(key))
+// 2) Compare(prefix(key), key) <= 0.
+// 3) If Compare(key1, key2) <= 0, then Compare(prefix(key1), prefix(key2)) <= 0
+bool Table::PrefixMayMatch(const Slice& internal_prefix) const {
+  FilterBlockReader* filter = rep_->filter;
+  bool may_match = true;
+  Status s;
+
+  if (filter == nullptr) {
+    return true;
+  }
+
+  Iterator* iiter = rep_->index_block->NewIterator(rep_->options.comparator);
+  iiter->Seek(internal_prefix);
+  if (! iiter->Valid()) {
+    // we're past end of file
+    may_match = false;
+  } else if (iiter->key().starts_with(internal_prefix)) {
+    // we need to check for this subtle case because our only
+    // guarantee is that "the key is a string >= last key in that data
+    // block" according to the doc/table_format.txt spec.
+    //
+    // Suppose iiter->key() starts with the desired prefix; it is not
+    // necessarily the case that the corresponding data block will
+    // contain the prefix, since iiter->key() need not be in the
+    // block.  However, the next data block may contain the prefix, so
+    // we return true to play it safe.
+    may_match = true;
+  } else {
+    // iiter->key() does NOT start with the desired prefix.  Because
+    // Seek() finds the first key that is >= the seek target, this
+    // means that iiter->key() > prefix.  Thus, any data blocks coming
+    // after the data block corresponding to iiter->key() cannot
+    // possibly contain the key.  Thus, the corresponding data block
+    // is the only one which could potentially contain the prefix.
+    Slice handle_value = iiter->value();
+    BlockHandle handle;
+    s = handle.DecodeFrom(&handle_value);
+    assert(s.ok());
+    may_match = filter->PrefixMayMatch(handle.offset(), internal_prefix);
+  }
+  delete iiter;
+  return may_match;
 }

 Iterator* Table::NewIterator(const ReadOptions& options) const {
+  if (options.prefix) {
+    InternalKey internal_prefix(*options.prefix, 0, kTypeValue);
+    if (!PrefixMayMatch(internal_prefix.Encode())) {
+      // nothing in this file can match the prefix, so we should not
+      // bother doing I/O to this file when iterating.
+      return NewEmptyIterator();
+    }
+  }
+
  return NewTwoLevelIterator(
      rep_->index_block->NewIterator(rep_->options.comparator),
-      &Table::BlockReader, const_cast<Table*>(this), options);
+      &Table::BlockReader, const_cast<Table*>(this), options, rep_->soptions);
 }

 Status Table::InternalGet(const ReadOptions& options, const Slice& k,
                          void* arg,
-                          void (*saver)(void*, const Slice&, const Slice&, bool)) {
+                          bool (*saver)(void*, const Slice&, const Slice&,
+                                        bool),
+                          void (*mark_key_may_exist)(void*),
+                          const bool no_io) {
  Status s;
  Iterator* iiter = rep_->index_block->NewIterator(rep_->options.comparator);
-  iiter->Seek(k);
-  if (iiter->Valid()) {
+  bool done = false;
+  for (iiter->Seek(k); iiter->Valid() && !done; iiter->Next()) {
    Slice handle_value = iiter->value();
    FilterBlockReader* filter = rep_->filter;
    BlockHandle handle;
@@ -284,14 +402,28 @@ Status Table::InternalGet(const ReadOptions& options, const Slice& k,
        handle.DecodeFrom(&handle_value).ok() &&
        !filter->KeyMayMatch(handle.offset(), k)) {
      // Not found
+      // TODO: think about interaction with Merge. If a user key cannot
+      // cross one data block, we should be fine.
      RecordTick(rep_->options.statistics, BLOOM_FILTER_USEFUL);
+      break;
    } else {
      bool didIO = false;
      Iterator* block_iter = BlockReader(this, options, iiter->value(),
-                                         &didIO);
-      block_iter->Seek(k);
-      if (block_iter->Valid()) {
-        (*saver)(arg, block_iter->key(), block_iter->value(), didIO);
+                                         &didIO, no_io);
+
+      if (no_io && !block_iter) { // couldn't get block from block_cache
+        // Update Saver.state to Found because we are only looking for whether
+        // we can guarantee the key is not there when "no_io" is set
+        (*mark_key_may_exist)(arg);
+        break;
+      }
+
+      // Call the *saver function on each entry/block until it returns false
+      for (block_iter->Seek(k); block_iter->Valid(); block_iter->Next()) {
+        if (!(*saver)(arg, block_iter->key(), block_iter->value(), didIO)) {
+          done = true;
+          break;
+        }
      }
      s = block_iter->status();
      delete block_iter;
@@ -304,8 +436,9 @@ Status Table::InternalGet(const ReadOptions& options, const Slice& k,
  return s;
 }

-void SaveDidIO(void* arg, const Slice& key, const Slice& value, bool didIO) {
+bool SaveDidIO(void* arg, const Slice& key, const Slice& value, bool didIO) {
  *reinterpret_cast<bool*>(arg) = didIO;
+  return false;
 }
 bool Table::TEST_KeyInCache(const ReadOptions& options, const Slice& key) {
  // We use InternalGet() as it has logic that checks whether we read the