Updating readme to 2.1

Summary: Test Plan: Reviewers: CC: Task ID: # Blame Rev:
Build fix with merge_test and ttl
2026-11-07 11:32:34 -05:00 · 2013-08-06 14:43:16 -07:00 · 2013-08-06 11:42:21 -07:00 · 2013-08-06 11:02:19 -07:00 · 2013-08-05 20:14:32 -07:00 · 2013-08-05 19:22:12 -07:00
181 changed files with 18179 additions and 3389 deletions
@@ -1,5 +1,10 @@
 {
  "project_id" : "leveldb",
  "conduit_uri" : "https://reviews.facebook.net/",
-  "copyright_holder" : ""
+  "copyright_holder" : "",
+  "load" : [
+    "linters/src/"
+  ],
+  "lint.engine" : "FacebookFbcodeLintEngine",
+  "lint.engine.single.linter" : "FbcodeCppLinter"
 }
@@ -6,6 +6,7 @@ build_config.mk
 *.so.*
 *_test
 *.arc
+*.d
 db_bench
 db_stress
 ldb
@@ -1,8 +0,0 @@
-# Names should be added to this file like so:
-# Name or Organization <email address>
-
-Google Inc.
-
-# Initial version authors:
-Jeffrey Dean <jeff@google.com>
-Sanjay Ghemawat <sanjay@google.com>
@@ -9,9 +9,8 @@ INSTALL_PATH ?= $(CURDIR)
 # Uncomment exactly one of the lines labelled (A), (B), and (C) below
 # to switch between compilation modes.

-# OPT ?= -O2 -DNDEBUG       # (A) Production use (optimized mode)
-# OPT ?= -g2              # (B) Debug mode, w/ full line-level debugging symbols
-OPT ?= -O2 -g2 -DNDEBUG -Wall # (C) Profiling mode: opt, but w/debugging symbols
+# OPT ?= -DNDEBUG     # (A) Production use (optimized mode)
+OPT += -O2 -fno-omit-frame-pointer -momit-leaf-frame-pointer
 #-----------------------------------------------

 # detect what platform we're building on
@@ -19,8 +18,9 @@ $(shell ./build_detect_platform build_config.mk)
 # this file is generated by the previous line to set build flags and sources
 include build_config.mk

-CFLAGS += -I. -I./include $(PLATFORM_CCFLAGS) $(OPT)
-CXXFLAGS += -I. -I./include $(PLATFORM_CXXFLAGS) $(OPT)
+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

 LDFLAGS += $(PLATFORM_LDFLAGS)

@@ -30,7 +30,10 @@ MEMENVOBJECTS = $(MEMENV_SOURCES:.cc=.o)

 TESTUTIL = ./util/testutil.o
 TESTHARNESS = ./util/testharness.o $(TESTUTIL)
-
+VALGRIND_ERROR = 2
+VALGRIND_DIR = VALGRIND_LOGS
+VALGRIND_VER := $(join $(VALGRIND_VER),valgrind)
+VALGRIND_OPTS = --error-exitcode=$(VALGRIND_ERROR) --leak-check=full

 TESTS = \
 	arena_test \
@@ -38,6 +41,7 @@ TESTS = \
 	c_test \
 	cache_test \
 	coding_test \
+	histogram_test \
 	corruption_test \
 	crc32c_test \
 	db_test \
@@ -49,25 +53,29 @@ TESTS = \
 	memenv_test \
 	skiplist_test \
 	table_test \
+	ttl_test \
 	block_test \
 	version_edit_test \
 	version_set_test \
 	reduce_levels_test \
 	write_batch_test \
-	filelock_test
+	auto_roll_logger_test \
+	filelock_test \
+	merge_test \
+	redis_test \
+	manual_compaction_test \
+	stringappend_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
-VERSIONFILE=util/build_version.cc

-LIBRARY = libleveldb.a
+LIBRARY = librocksdb.a
 MEMENVLIBRARY = libmemenv.a

 default: all
@@ -76,15 +84,15 @@ default: all
 ifneq ($(PLATFORM_SHARED_EXT),)

 ifneq ($(PLATFORM_SHARED_VERSIONED),true)
-SHARED1 = libleveldb.$(PLATFORM_SHARED_EXT)
+SHARED1 = librocksdb.$(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 = librocksdb.$(PLATFORM_SHARED_EXT)
 SHARED2 = $(SHARED1).$(SHARED_MAJOR)
 SHARED3 = $(SHARED1).$(SHARED_MAJOR).$(SHARED_MINOR)
 SHARED = $(SHARED1) $(SHARED2) $(SHARED3)
@@ -99,14 +107,43 @@ $(SHARED3):

 endif  # PLATFORM_SHARED_EXT

-all: $(VERSIONFILE) $(SHARED) $(LIBRARY) $(TOOLS)
+all: $(SHARED) $(LIBRARY) $(PROGRAMS)

-check: all $(PROGRAMS) $(TESTS) $(TOOLS)
+release:
+	make clean
+	OPT=-DNDEBUG make -j32
+
+check: all $(PROGRAMS) $(TESTS) $(TOOLS) ldb_tests
 	for t in $(TESTS); do echo "***** Running $$t"; ./$$t || exit 1; done

+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)
+	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 \
+		stime=`date '+%s'`; \
+		$(VALGRIND_VER) $(VALGRIND_OPTS) ./$$t; \
+		if [ $$? -eq $(VALGRIND_ERROR) ] ; then \
+			echo $$t >> $(VALGRIND_DIR)/valgrind_failed_tests; \
+		fi; \
+		etime=`date '+%s'`; \
+		echo $$t $$((etime - stime)) >> $(VALGRIND_DIR)/valgrind_tests_times; \
+	done
+
 clean:
-	-rm -f $(PROGRAMS) $(BENCHMARKS) $(LIBRARY) $(SHARED) $(MEMENVLIBRARY) $(THRIFTSERVER) */*.o */*/*.o ios-x86/*/*.o ios-arm/*/*.o build_config.mk $(VERSIONFILE)
+	-rm -f $(PROGRAMS) $(BENCHMARKS) $(LIBRARY) $(SHARED) $(MEMENVLIBRARY) $(THRIFTSERVER) build_config.mk
 	-rm -rf ios-x86/* ios-arm/*
+	-for x in `find . -name "*.[od]"`; do rm $$x; done

 $(LIBRARY): $(LIBOBJECTS)
 	rm -f $@
@@ -123,103 +160,121 @@ db_repl_stress: tools/db_repl_stress.o $(LIBOBJECTS) $(TESTUTIL)
 	$(CXX) tools/db_repl_stress.o $(LIBOBJECTS) $(TESTUTIL) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS)

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

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

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

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

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

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

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

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

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

 db_test: db/db_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) db/db_test.o $(LIBOBJECTS) $(TESTHARNESS) -o $@ $(LDFLAGS)
+	$(CXX) db/db_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)

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

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

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

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

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

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

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

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

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

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

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

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

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

-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) -o $@ $(LDFLAGS)
+manual_compaction_test: util/manual_compaction_test.o $(LIBOBJECTS) $(TESTHARNESS)
+	$(CXX) util/manual_compaction_test.o $(LIBOBJECTS) $(TESTHARNESS) $(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) -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)

-manifest_dump: tools/manifest_dump.o $(LIBOBJECTS)
-	$(CXX) tools/manifest_dump.o $(LIBOBJECTS) -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)

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

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

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

-# recreate the version file with the latest git revision
-$(VERSIONFILE):	build_detect_version
-	$(shell ./build_detect_platform build_config.mk)
-
-# recreate the version file with the latest git revision
-$(VERSIONFILE):	build_detect_version
-	$(shell ./build_detect_platform build_config.mk)
+.PHONY: tags
+tags:
+	ctags `find . -name '*.cc'` `find . -name '*.h'`
+	cscope -b `find . -name '*.cc'` `find . -name '*.h'`

 ifeq ($(PLATFORM), IOS)
 # For iOS, create universal object files to be used on both the simulator and
@@ -250,3 +305,18 @@ else
 .c.o:
 	$(CC) $(CFLAGS) $(PLATFORM_SHARED_CFLAGS) -c $< -o $@
 endif
+
+%.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
+
+DEPFILES = $(filter-out util/build_version.d,$(SOURCES:.cc=.d))
+
+depend: $(DEPFILES)
+
+ifneq ($(MAKECMDGOALS),clean)
+-include $(DEPFILES)
+endif
+
@@ -1,17 +0,0 @@
-Release 1.2 2011-05-16
----------------------
-
-Fixes for larger databases (tested up to one billion 100-byte entries,
-i.e., ~100GB).
-
-(1) Place hard limit on number of level-0 files.  This fixes errors
-of the form "too many open files".
-
-(2) Fixed memtable management.  Before the fix, a heavy write burst
-could cause unbounded memory usage.
-
-A fix for a logging bug where the reader would incorrectly complain
-about corruption.
-
-Allow public access to WriteBatch contents so that users can easily
-wrap a DB.
@@ -1,7 +1,9 @@
 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 
+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.
 It has an Log-Stuctured-Merge-Database (LSM) design with flexible tradeoffs
 between Write-Amplification-Factor(WAF), Read-Amplification-Factor (RAF)
@@ -11,9 +13,6 @@ single database.

 The core of this code has been derived from open-source leveldb.

-leveldb: A key-value store
-Authors: Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
-
 The code under this directory implements a system for maintaining a
 persistent key/value store.

@@ -59,6 +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.
+
+
@@ -1,12 +1,3 @@
-* How to compile using fbcode and jemalloc
-  source fbcode.sh
-  make 
+* Detailed instructions on how to compile using fbcode and jemalloc

-* Compiling for CPUs with SSE4 support
-
-  make OPT='-O2 -DNDEBUG -msse -msse4.2'
-  
-  This makes CRC computation much faster, but
-  binaries won't run on CPUs that don't support it.
-
-* Latest release is 1.5.7.fb
+* Latest release is 2.1.fb
@@ -1,13 +0,0 @@
-ss
- Stats
-
-db
- Maybe implement DB::BulkDeleteForRange(start_key, end_key)
-  that would blow away files whose ranges are entirely contained
-  within [start_key..end_key]?  For Chrome, deletion of obsolete
-  object stores, etc. can be done in the background anyway, so
-  probably not that important.
-
-After a range is completely deleted, what gets rid of the
-corresponding files if we do no future changes to that range.  Make
-the conditions for triggering compactions fire in more situations?
@@ -0,0 +1,4 @@
+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
@@ -28,6 +28,15 @@ if test -z "$OUTPUT"; then
  exit 1
 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
+    else
+        source ./fbcode.clang31.sh
+    fi
+fi
+
 # Delete existing output, if it exists
 rm -f $OUTPUT
 touch $OUTPUT
@@ -45,66 +54,72 @@ if test -z "$TARGET_OS"; then
    TARGET_OS=`uname -s`
 fi

-COMMON_FLAGS=
+COMMON_FLAGS="${CFLAGS}"
 CROSS_COMPILE=
 PLATFORM_CCFLAGS=
-PLATFORM_CXXFLAGS=
-PLATFORM_LDFLAGS=
+PLATFORM_CXXFLAGS="${CXXFLAGS}"
+PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS"
 PLATFORM_SHARED_EXT="so"
-PLATFORM_SHARED_LDFLAGS="-shared -Wl,-soname -Wl,"
+PLATFORM_SHARED_LDFLAGS="${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=`find port -name '*.cc' | tr "\n" " "`
+
 # On GCC, we pick libc's memcmp over GCC's memcmp via -fno-builtin-memcmp
 case "$TARGET_OS" in
    Darwin)
        PLATFORM=OS_MACOSX
-        COMMON_FLAGS="-fno-builtin-memcmp -DOS_MACOSX"
+        COMMON_FLAGS="$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="-I/usr/include -fno-builtin-memcmp -pthread -DOS_LINUX -fPIC"
-        PLATFORM_LDFLAGS="-pthread"
-        PORT_FILE=port/port_posix.cc
+        COMMON_FLAGS="$COMMON_FLAGS -DOS_LINUX -fPIC"
+        if [ -z "$USE_CLANG" ]; then
+            COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp"
+        fi
+        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lpthread"
+        # PORT_FILES=port/linux/linux_specific.cc
        ;;
    SunOS)
        PLATFORM=OS_SOLARIS
-        COMMON_FLAGS="-fno-builtin-memcmp -D_REENTRANT -DOS_SOLARIS"
-        PLATFORM_LDFLAGS="-lpthread -lrt"
-        PORT_FILE=port/port_posix.cc
+        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_SOLARIS"
+        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lpthread -lrt"
+        # PORT_FILES=port/sunos/sunos_specific.cc
        ;;
    FreeBSD)
        PLATFORM=OS_FREEBSD
-        COMMON_FLAGS="-fno-builtin-memcmp -D_REENTRANT -DOS_FREEBSD"
-        PLATFORM_LDFLAGS="-lpthread"
-        PORT_FILE=port/port_posix.cc
+        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_FREEBSD"
+        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lpthread"
+        # PORT_FILES=port/freebsd/freebsd_specific.cc
        ;;
    NetBSD)
        PLATFORM=OS_NETBSD
-        COMMON_FLAGS="-fno-builtin-memcmp -D_REENTRANT -DOS_NETBSD"
-        PLATFORM_LDFLAGS="-lpthread -lgcc_s"
-        PORT_FILE=port/port_posix.cc
+        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_NETBSD"
+        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lpthread -lgcc_s"
+        # PORT_FILES=port/netbsd/netbsd_specific.cc
        ;;
    OpenBSD)
        PLATFORM=OS_OPENBSD
-        COMMON_FLAGS="-fno-builtin-memcmp -D_REENTRANT -DOS_OPENBSD"
-        PLATFORM_LDFLAGS="-pthread"
-        PORT_FILE=port/port_posix.cc
+        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_OPENBSD"
+        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -pthread"
+        # PORT_FILES=port/openbsd/openbsd_specific.cc
        ;;
    DragonFly)
        PLATFORM=OS_DRAGONFLYBSD
-        COMMON_FLAGS="-fno-builtin-memcmp -D_REENTRANT -DOS_DRAGONFLYBSD"
-        PLATFORM_LDFLAGS="-lpthread"
-        PORT_FILE=port/port_posix.cc
+        COMMON_FLAGS="$COMMON_FLAGS -fno-builtin-memcmp -D_REENTRANT -DOS_DRAGONFLYBSD"
+        PLATFORM_LDFLAGS="$PLATFORM_LDFLAGS -lpthread"
+        # PORT_FILES=port/dragonfly/dragonfly_specific.cc
        ;;
    OS_ANDROID_CROSSCOMPILE)
        PLATFORM=OS_ANDROID
-	COMMON_FLAGS="-fno-builtin-memcmp -D_REENTRANT -DOS_ANDROID -DLEVELDB_PLATFORM_POSIX"
-	PLATFORM_LDFLAGS=""  # All pthread features are in the Android C library
-        PORT_FILE=port/port_posix.cc
+	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_FILES=port/android/android.cc
        CROSS_COMPILE=true
        ;;
    *)
@@ -118,7 +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
@@ -137,7 +152,7 @@ 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

@@ -226,10 +241,13 @@ COMMON_FLAGS="$COMMON_FLAGS $USE_SSE"
 PLATFORM_CCFLAGS="$PLATFORM_CCFLAGS $COMMON_FLAGS"
 PLATFORM_CXXFLAGS="$PLATFORM_CXXFLAGS $COMMON_FLAGS"

+VALGRIND_VER="$VALGRIND_VER"
+
 echo "CC=$CC" >> $OUTPUT
 echo "CXX=$CXX" >> $OUTPUT
 echo "PLATFORM=$PLATFORM" >> $OUTPUT
 echo "PLATFORM_LDFLAGS=$PLATFORM_LDFLAGS" >> $OUTPUT
+echo "VALGRIND_VER=$VALGRIND_VER" >> $OUTPUT
 echo "PLATFORM_CCFLAGS=$PLATFORM_CCFLAGS" >> $OUTPUT
 echo "PLATFORM_CXXFLAGS=$PLATFORM_CXXFLAGS" >> $OUTPUT
 echo "PLATFORM_SHARED_CFLAGS=$PLATFORM_SHARED_CFLAGS" >> $OUTPUT
@@ -237,3 +255,4 @@ echo "PLATFORM_SHARED_EXT=$PLATFORM_SHARED_EXT" >> $OUTPUT
 echo "PLATFORM_SHARED_LDFLAGS=$PLATFORM_SHARED_LDFLAGS" >> $OUTPUT
 echo "PLATFORM_SHARED_VERSIONED=$PLATFORM_SHARED_VERSIONED" >> $OUTPUT
 echo "THRIFTSERVER=$THRIFTSERVER" >> $OUTPUT
+echo "EXEC_LDFLAGS=$EXEC_LDFLAGS" >> $OUTPUT
@@ -8,13 +8,14 @@
 #

 # create git version file
-VFILE=util/build_version.cc
+VFILE=$(mktemp)
+trap "rm $VFILE" EXIT

 # check to see if git is in the path
 which git > /dev/null

 if [ "$?" = 0 ]; then
-  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}
+  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
@@ -22,3 +23,8 @@ 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
@@ -6,38 +6,142 @@

 #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) {
+                  FileMetaData* meta,
+                  const Comparator* user_comparator,
+                  const SequenceNumber newest_snapshot,
+                  const SequenceNumber earliest_seqno_in_memtable) {
  Status s;
  meta->file_size = 0;
  iter->SeekToFirst();

+  // If the sequence number of the smallest entry in the memtable is
+  // smaller than the most recent snapshot, then we do not trigger
+  // removal of duplicate/deleted keys as part of this builder.
+  bool purge = options.purge_redundant_kvs_while_flush;
+  if (earliest_seqno_in_memtable <= newest_snapshot) {
+    purge = false;
+  }
+
  std::string fname = TableFileName(dbname, meta->number);
  if (iter->Valid()) {
-    WritableFile* file;
-    s = env->NewWritableFile(fname, &file);
+    unique_ptr<WritableFile> file;
+    s = env->NewWritableFile(fname, &file, soptions);
    if (!s.ok()) {
      return s;
    }
+    TableBuilder* builder = new TableBuilder(options, file.get(), 0);

-    TableBuilder* builder = new TableBuilder(options, file, 0);
+    // the first key is the smallest key
    meta->smallest.DecodeFrom(iter->key());
-    for (; iter->Valid(); iter->Next()) {
-      Slice key = iter->key();
-      meta->largest.DecodeFrom(key);
-      builder->Add(key, iter->value());
+
+    MergeHelper merge(user_comparator, options.merge_operator,
+                      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_key;
+      bool is_first_key = true;    // Also write if this is the very first key
+
+      while (iter->Valid()) {
+        bool iterator_at_next = false;
+
+        // Get current key
+        ParsedInternalKey this_ikey;
+        Slice key = iter->key();
+        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 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);
+        } 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();
+      }
+
+      // The last key is the largest key
+      meta->largest.DecodeFrom(Slice(prev_key));
+
+    } else {
+      for (; iter->Valid(); iter->Next()) {
+        Slice key = iter->key();
+        meta->largest.DecodeFrom(key);
+        builder->Add(key, iter->value());
+      }
    }

    // Finish and check for builder errors
@@ -55,20 +159,21 @@ 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();
      }
    }
    if (s.ok()) {
      s = file->Close();
    }
-    delete file;
-    file = NULL;

    if (s.ok()) {
      // Verify that the table is usable
      Iterator* it = table_cache->NewIterator(ReadOptions(),
+                                              soptions,
                                              meta->number,
                                              meta->file_size);
      s = it->status();
@@ -5,7 +5,9 @@
 #ifndef STORAGE_LEVELDB_DB_BUILDER_H_
 #define STORAGE_LEVELDB_DB_BUILDER_H_

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

 namespace leveldb {

@@ -13,6 +15,7 @@ struct Options;
 struct FileMetaData;

 class Env;
+class EnvOptions;
 class Iterator;
 class TableCache;
 class VersionEdit;
@@ -25,9 +28,13 @@ class VersionEdit;
 extern Status BuildTable(const std::string& dbname,
                         Env* env,
                         const Options& options,
+                         const EnvOptions& soptions,
                         TableCache* table_cache,
                         Iterator* iter,
-                         FileMetaData* meta);
+                         FileMetaData* meta,
+                         const Comparator* user_comparator,
+                         const SequenceNumber newest_snapshot,
+                         const SequenceNumber earliest_seqno_in_memtable);

 }  // namespace leveldb

@@ -39,6 +39,8 @@ using leveldb::WritableFile;
 using leveldb::WriteBatch;
 using leveldb::WriteOptions;

+using std::shared_ptr;
+
 extern "C" {

 struct leveldb_t              { DB*               rep; };
@@ -48,12 +50,12 @@ struct leveldb_snapshot_t     { const Snapshot*   rep; };
 struct leveldb_readoptions_t  { ReadOptions       rep; };
 struct leveldb_writeoptions_t { WriteOptions      rep; };
 struct leveldb_options_t      { Options           rep; };
-struct leveldb_cache_t        { Cache*            rep; };
 struct leveldb_seqfile_t      { SequentialFile*   rep; };
 struct leveldb_randomfile_t   { RandomAccessFile* rep; };
 struct leveldb_writablefile_t { WritableFile*     rep; };
-struct leveldb_logger_t       { Logger*           rep; };
 struct leveldb_filelock_t     { FileLock*         rep; };
+struct leveldb_logger_t       { shared_ptr<Logger>  rep; };
+struct leveldb_cache_t        { shared_ptr<Cache>   rep; };

 struct leveldb_comparator_t : public Comparator {
  void* state_;
@@ -421,7 +423,9 @@ void leveldb_options_set_env(leveldb_options_t* opt, leveldb_env_t* env) {
 }

 void leveldb_options_set_info_log(leveldb_options_t* opt, leveldb_logger_t* l) {
-  opt->rep.info_log = (l ? l->rep : NULL);
+  if (l) {
+    opt->rep.info_log = l->rep;
+  }
 }

 void leveldb_options_set_write_buffer_size(leveldb_options_t* opt, size_t s) {
@@ -433,7 +437,9 @@ void leveldb_options_set_max_open_files(leveldb_options_t* opt, int n) {
 }

 void leveldb_options_set_cache(leveldb_options_t* opt, leveldb_cache_t* c) {
-  opt->rep.block_cache = c->rep;
+  if (c) {
+    opt->rep.block_cache = c->rep;
+  }
 }

 void leveldb_options_set_block_size(leveldb_options_t* opt, size_t s) {
@@ -502,6 +508,16 @@ void leveldb_options_set_compression(leveldb_options_t* opt, int t) {
  opt->rep.compression = static_cast<CompressionType>(t);
 }

+void leveldb_options_set_compression_per_level(leveldb_options_t* opt,
+                                               int* level_values,
+                                               size_t num_levels) {
+  opt->rep.compression_per_level.resize(num_levels);
+  for (size_t i = 0; i < num_levels; ++i) {
+    opt->rep.compression_per_level[i] =
+      static_cast<CompressionType>(level_values[i]);
+  }
+}
+
 void leveldb_options_set_compression_options(
    leveldb_options_t* opt, int w_bits, int level, int strategy) {
  opt->rep.compression_opts.window_bits = w_bits;
@@ -647,7 +663,6 @@ leveldb_cache_t* leveldb_cache_create_lru(size_t capacity) {
 }

 void leveldb_cache_destroy(leveldb_cache_t* cache) {
-  delete cache->rep;
  delete cache;
 }

@@ -188,6 +188,9 @@ int main(int argc, char** argv) {
  leveldb_options_set_block_restart_interval(options, 8);
  leveldb_options_set_compression(options, leveldb_no_compression);
  leveldb_options_set_compression_options(options, -14, -1, 0);
+  int compression_levels[] = {leveldb_no_compression, leveldb_no_compression,
+                              leveldb_no_compression, leveldb_no_compression};
+  leveldb_options_set_compression_per_level(options, compression_levels, 4);

  roptions = leveldb_readoptions_create();
  leveldb_readoptions_set_verify_checksums(roptions, 1);
@@ -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"
@@ -28,7 +28,7 @@ class CorruptionTest {
 public:
  test::ErrorEnv env_;
  std::string dbname_;
-  Cache* tiny_cache_;
+  shared_ptr<Cache> tiny_cache_;
  Options options_;
  DB* db_;

@@ -38,8 +38,9 @@ class CorruptionTest {
    dbname_ = test::TmpDir() + "/db_test";
    DestroyDB(dbname_, options_);

-    db_ = NULL;
+    db_ = nullptr;
    options_.create_if_missing = true;
+    options_.block_size_deviation = 0; // make unit test pass for now
    Reopen();
    options_.create_if_missing = false;
  }
@@ -47,25 +48,26 @@ class CorruptionTest {
  ~CorruptionTest() {
     delete db_;
     DestroyDB(dbname_, Options());
-     delete tiny_cache_;
  }

-  Status TryReopen(Options* options = NULL) {
+  Status TryReopen(Options* options = nullptr) {
    delete db_;
-    db_ = NULL;
+    db_ = nullptr;
    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_);
  }

-  void Reopen(Options* options = NULL) {
+  void Reopen(Options* options = nullptr) {
    ASSERT_OK(TryReopen(options));
  }

  void RepairDB() {
    delete db_;
-    db_ = NULL;
+    db_ = nullptr;
    ASSERT_OK(::leveldb::RepairDB(dbname_, options_));
  }

@@ -229,8 +231,8 @@ TEST(CorruptionTest, TableFile) {
  Build(100);
  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
  dbi->TEST_CompactMemTable();
-  dbi->TEST_CompactRange(0, NULL, NULL);
-  dbi->TEST_CompactRange(1, NULL, NULL);
+  dbi->TEST_CompactRange(0, nullptr, nullptr);
+  dbi->TEST_CompactRange(1, nullptr, nullptr);

  Corrupt(kTableFile, 100, 1);
  Check(99, 99);
@@ -278,7 +280,7 @@ TEST(CorruptionTest, CorruptedDescriptor) {
  ASSERT_OK(db_->Put(WriteOptions(), "foo", "hello"));
  DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
  dbi->TEST_CompactMemTable();
-  dbi->TEST_CompactRange(0, NULL, NULL);
+  dbi->TEST_CompactRange(0, nullptr, nullptr);

  Corrupt(kDescriptorFile, 0, 1000);
  Status s = TryReopen();
@@ -17,12 +17,14 @@ 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();
 }

@@ -5,8 +5,10 @@
 #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"
@@ -16,6 +18,7 @@
 #include "port/port.h"
 #include "util/stats_logger.h"
 #include "memtablelist.h"
+#include "leveldb/memtablerep.h"

 #ifdef USE_SCRIBE
 #include "scribe/scribe_logger.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();
@@ -57,11 +75,11 @@ class DBImpl : public DB {
                              uint64_t* manifest_file_size);
  virtual SequenceNumber GetLatestSequenceNumber();
  virtual Status GetUpdatesSince(SequenceNumber seq_number,
-                                 TransactionLogIterator ** iter);
+                                 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.
@@ -85,19 +103,29 @@ class DBImpl : public DB {
  // Simulate a db crash, no elegant closing of database.
  void TEST_Destroy_DBImpl();

+  // 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_;
-  VersionSet* versions_;
+  unique_ptr<VersionSet> versions_;
  const InternalKeyComparator internal_comparator_;
  const Options options_;  // options_.comparator == &internal_comparator_

  const Comparator* user_comparator() const {
    return internal_comparator_.user_comparator();
  }
+
  MemTable* GetMemTable() {
    return mem_;
-  } 
+  }
+
+  Iterator* NewInternalIterator(const ReadOptions&,
+                                SequenceNumber* latest_snapshot);

 private:
  friend class DB;
@@ -105,15 +133,12 @@ class DBImpl : public DB {
  struct Writer;
  struct DeletionState;

-  Iterator* NewInternalIterator(const ReadOptions&,
-                                SequenceNumber* latest_snapshot);
-
  Status NewDB();

  // Recover the descriptor from persistent storage.  May do a significant
  // amount of work to recover recently logged updates.  Any changes to
  // be made to the descriptor are added to *edit.
-  Status Recover(VersionEdit* edit, MemTable* external_table = NULL,
+  Status Recover(VersionEdit* edit, MemTable* external_table = nullptr,
      bool error_if_log_file_exist = false);

  void MaybeIgnoreError(Status* s) const;
@@ -125,7 +150,7 @@ class DBImpl : public DB {

  // Compact the in-memory write buffer to disk.  Switches to a new
  // log-file/memtable and writes a new descriptor iff successful.
-  Status CompactMemTable(bool* madeProgress = NULL);
+  Status CompactMemTable(bool* madeProgress = nullptr);

  Status RecoverLogFile(uint64_t log_number,
                        VersionEdit* edit,
@@ -138,9 +163,10 @@ 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);

@@ -191,38 +217,51 @@ class DBImpl : public DB {
  Status FindProbableWALFiles(std::vector<LogFile>* const allLogs,
                              std::vector<LogFile>* const result,
                              const SequenceNumber target);
-
+  //  return true if
+  bool CheckFileExistsAndEmpty(const LogFile& file);

  Status ReadFirstRecord(const LogFile& file, 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_;
-  bool owns_cache_;

  // table_cache_ provides its own synchronization
-  TableCache* table_cache_;
+  unique_ptr<TableCache> table_cache_;

-  // Lock over the persistent DB state.  Non-NULL iff successfully acquired.
+  // Lock over the persistent DB state.  Non-nullptr iff successfully acquired.
  FileLock* db_lock_;

  // State below is protected by mutex_
  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
-  WritableFile* logfile_;
  uint64_t logfile_number_;
-  log::Writer* log_;
+  unique_ptr<log::Writer> log_;

  std::string host_name_;

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

  SnapshotList snapshots_;

@@ -241,8 +280,8 @@ class DBImpl : public DB {
    int level;
    bool done;
    bool in_progress;           // compaction request being processed?
-    const InternalKey* begin;   // NULL means beginning of key range
-    const InternalKey* end;     // NULL means end of key range
+    const InternalKey* begin;   // nullptr means beginning of key range
+    const InternalKey* end;     // nullptr means end of key range
    InternalKey tmp_storage;    // Used to keep track of compaction progress
  };
  ManualCompaction* manual_compaction_;
@@ -250,7 +289,7 @@ 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;

@@ -260,11 +299,21 @@ 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_;
-  uint64_t stall_leveln_slowdown_;
+  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_;
@@ -274,7 +323,7 @@ class DBImpl : public DB {
  // Per level compaction stats.  stats_[level] stores the stats for
  // compactions that produced data for the specified "level".
  struct CompactionStats {
-    int64_t micros;
+    uint64_t micros;

    // Bytes read from level N during compaction between levels N and N+1
    int64_t bytes_readn;
@@ -314,7 +363,20 @@ 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_;
@@ -322,6 +384,19 @@ class DBImpl : public DB {
  // count of the number of contiguous delaying writes
  int delayed_writes_;

+  // store the last flushed sequence.
+  // 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&);
@@ -329,9 +404,20 @@ 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"
@@ -50,28 +50,33 @@ Status DBImplReadOnly::Get(const ReadOptions& options,
                   const Slice& key,
                   std::string* value) {
  Status s;
+  MemTable* mem = GetMemTable();
  Version* current = versions_->current();
  SequenceNumber snapshot = versions_->LastSequence();
+  std::deque<std::string> merge_operands;
  LookupKey lkey(key, snapshot);
-  Version::GetStats stats;
-  s = current->Get(options, lkey, value, &stats);
+  if (mem->Get(lkey, value, &s, &merge_operands, options_)) {
+  } else {
+    Version::GetStats stats;
+    current->Get(options, lkey, value, &s, &merge_operands, &stats, options_);
+  }
  return s;
 }

 Iterator* DBImplReadOnly::NewIterator(const ReadOptions& options) {
-  std::vector<Iterator*> list;
-  versions_->current()->AddIterators(options, &list);
-  Iterator* internal_iter =
-      NewMergingIterator(&internal_comparator_, &list[0], list.size());
+  SequenceNumber latest_snapshot;
+  Iterator* internal_iter = NewInternalIterator(options, &latest_snapshot);
  return NewDBIterator(
-      &dbname_, env_, user_comparator(), internal_iter,
-      reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_);
+    &dbname_, env_, options_,  user_comparator(),internal_iter,
+      (options.snapshot != nullptr
+      ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
+      : latest_snapshot));
 }


 Status DB::OpenForReadOnly(const Options& options, const std::string& dbname,
                DB** dbptr, bool error_if_log_file_exist) {
-  *dbptr = NULL;
+  *dbptr = nullptr;

  DBImplReadOnly* impl = new DBImplReadOnly(options, dbname);
  impl->mutex_.Lock();
@@ -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),
        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 +166,152 @@ 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;
+            // Go to a different state machine
+            MergeValuesNewToOld();
+            // TODO: what if !iter_->Valid()
+            return;
+            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() {
+  // TODO: Is there a way to unite with MergeHelper or other similar code?
+
+  // 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_->Merge(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_->Merge(ikey.user_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 +386,7 @@ 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 +397,21 @@ 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 +423,12 @@ 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);

@@ -2,48 +2,60 @@
 // 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_STORAGE_DB_DB_STATISTICS_H_
+#define LEVELDB_STORAGE_DB_DB_STATISTICS_H_
+
 #include <cassert>
 #include <stdlib.h>
 #include <vector>
+#include <memory>

 #include "leveldb/statistics.h"
+#include "util/histogram.h"
 #include "port/port.h"
 #include "util/mutexlock.h"
+
+
 namespace leveldb {

 class DBStatistics: public Statistics {
 public:
-  DBStatistics() : allTickers_(TICKER_ENUM_MAX) { }
+  DBStatistics() : allTickers_(TICKER_ENUM_MAX),
+                   allHistograms_(HISTOGRAM_ENUM_MAX) { }

-  void incNumFileOpens() {
-    MutexLock l(&mu_);
-    numFileOpens_++;
-  }
+  virtual ~DBStatistics() {}

-  void incNumFileCloses() {
-    MutexLock l(&mu_);
-    numFileCloses_++;
-  }
-
-  void incNumFileErrors() {
-    MutexLock l(&mu_);
-    numFileErrors_++;
-  }
-
-  long getTickerCount(Tickers tickerType) {
+  virtual long getTickerCount(Tickers tickerType) {
    assert(tickerType < TICKER_ENUM_MAX);
    return allTickers_[tickerType].getCount();
  }

-  void recordTick(Tickers tickerType) {
+  virtual void recordTick(Tickers tickerType, uint64_t count) {
    assert(tickerType < TICKER_ENUM_MAX);
-    allTickers_[tickerType].recordTick();
+    allTickers_[tickerType].recordTick(count);
+  }
+
+  virtual void measureTime(Histograms histogramType, uint64_t value) {
+    assert(histogramType < HISTOGRAM_ENUM_MAX);
+    allHistograms_[histogramType].Add(value);
+  }
+
+  virtual void histogramData(Histograms histogramType,
+                             HistogramData * const data) {
+    assert(histogramType < HISTOGRAM_ENUM_MAX);
+    allHistograms_[histogramType].Data(data);
  }

- private:
-  port::Mutex mu_;
  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_
+

@@ -44,7 +44,7 @@ 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 {
@@ -24,7 +24,8 @@ class InternalKey;
 // data structures.
 enum ValueType {
  kTypeDeletion = 0x0,
-  kTypeValue = 0x1
+  kTypeValue = 0x1,
+  kTypeMerge = 0x2
 };
 // kValueTypeForSeek defines the ValueType that should be passed when
 // constructing a ParsedInternalKey object for seeking to a particular
@@ -32,7 +33,7 @@ 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 +86,13 @@ 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 +160,17 @@ 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
+inline void UpdateInternalKey(char* internal_key,
+                              const size_t internal_key_size,
+                              uint64_t seq, ValueType t) {
+  assert(internal_key_size >= 8);
+  char* seqtype = internal_key + internal_key_size - 8;
+  uint64_t newval = (seq << 8) | t;
+  EncodeFixed64(seqtype, newval);
 }

 // A helper class useful for DBImpl::Get()
@@ -145,7 +145,8 @@ bool ParseFileName(const std::string& fname,
    *type = kInfoLogFile;
  } else if (rest.starts_with("LOG.old.")) {
    uint64_t ts_suffix;
-    rest.remove_prefix(sizeof("LOG.old."));
+    // sizeof also counts the trailing '\0'.
+    rest.remove_prefix(sizeof("LOG.old.") - 1);
    if (!ConsumeDecimalNumber(&rest, &ts_suffix)) {
      return false;
    }
@@ -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;
@@ -15,9 +15,9 @@ namespace log {
 Reader::Reporter::~Reporter() {
 }

-Reader::Reader(SequentialFile* file, Reporter* reporter, bool checksum,
-               uint64_t initial_offset)
-    : file_(file),
+Reader::Reader(unique_ptr<SequentialFile>&& file, Reporter* reporter,
+               bool checksum, uint64_t initial_offset)
+    : file_(std::move(file)),
      reporter_(reporter),
      checksum_(checksum),
      backing_store_(new char[kBlockSize]),
@@ -170,7 +170,7 @@ void Reader::ReportCorruption(size_t bytes, const char* reason) {
 }

 void Reader::ReportDrop(size_t bytes, const Status& reason) {
-  if (reporter_ != NULL &&
+  if (reporter_ != nullptr &&
      end_of_buffer_offset_ - buffer_.size() - bytes >= initial_offset_) {
    reporter_->Corruption(bytes, reason);
  }
@@ -5,6 +5,7 @@
 #ifndef STORAGE_LEVELDB_DB_LOG_READER_H_
 #define STORAGE_LEVELDB_DB_LOG_READER_H_

+#include <memory>
 #include <stdint.h>

 #include "db/log_format.h"
@@ -14,6 +15,7 @@
 namespace leveldb {

 class SequentialFile;
+using std::unique_ptr;

 namespace log {

@@ -32,7 +34,7 @@ class Reader {
  // Create a reader that will return log records from "*file".
  // "*file" must remain live while this Reader is in use.
  //
-  // If "reporter" is non-NULL, it is notified whenever some data is
+  // If "reporter" is non-nullptr, it is notified whenever some data is
  // dropped due to a detected corruption.  "*reporter" must remain
  // live while this Reader is in use.
  //
@@ -40,8 +42,8 @@ class Reader {
  //
  // The Reader will start reading at the first record located at physical
  // position >= initial_offset within the file.
-  Reader(SequentialFile* file, Reporter* reporter, bool checksum,
-         uint64_t initial_offset);
+  Reader(unique_ptr<SequentialFile>&& file, Reporter* reporter,
+         bool checksum, uint64_t initial_offset);

  ~Reader();

@@ -57,8 +59,21 @@ 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:
-  SequentialFile* const file_;
+  const unique_ptr<SequentialFile> file_;
  Reporter* const reporter_;
  bool const checksum_;
  char* const backing_store_;
@@ -100,8 +100,26 @@ class LogTest {
    }
  };

-  StringDest dest_;
-  StringSource source_;
+  std::string& dest_contents() {
+    auto dest = dynamic_cast<StringDest*>(writer_.file());
+    assert(dest);
+    return dest->contents_;
+  }
+
+  const std::string& dest_contents() const {
+    auto dest = dynamic_cast<const StringDest*>(writer_.file());
+    assert(dest);
+    return dest->contents_;
+  }
+
+  void reset_source_contents() {
+    auto src = dynamic_cast<StringSource*>(reader_.file());
+    assert(src);
+    src->contents_ = dest_contents();
+  }
+
+  unique_ptr<StringDest> dest_holder_;
+  unique_ptr<StringSource> source_holder_;
  ReportCollector report_;
  bool reading_;
  Writer writer_;
@@ -112,9 +130,11 @@ class LogTest {
  static uint64_t initial_offset_last_record_offsets_[];

 public:
-  LogTest() : reading_(false),
-              writer_(&dest_),
-              reader_(&source_, &report_, true/*checksum*/,
+  LogTest() : dest_holder_(new StringDest),
+              source_holder_(new StringSource),
+              reading_(false),
+              writer_(std::move(dest_holder_)),
+              reader_(std::move(source_holder_), &report_, true/*checksum*/,
                      0/*initial_offset*/) {
  }

@@ -124,13 +144,13 @@ class LogTest {
  }

  size_t WrittenBytes() const {
-    return dest_.contents_.size();
+    return dest_contents().size();
  }

  std::string Read() {
    if (!reading_) {
      reading_ = true;
-      source_.contents_ = Slice(dest_.contents_);
+      reset_source_contents();
    }
    std::string scratch;
    Slice record;
@@ -142,26 +162,27 @@ class LogTest {
  }

  void IncrementByte(int offset, int delta) {
-    dest_.contents_[offset] += delta;
+    dest_contents()[offset] += delta;
  }

  void SetByte(int offset, char new_byte) {
-    dest_.contents_[offset] = new_byte;
+    dest_contents()[offset] = new_byte;
  }

  void ShrinkSize(int bytes) {
-    dest_.contents_.resize(dest_.contents_.size() - bytes);
+    dest_contents().resize(dest_contents().size() - bytes);
  }

  void FixChecksum(int header_offset, int len) {
    // Compute crc of type/len/data
-    uint32_t crc = crc32c::Value(&dest_.contents_[header_offset+6], 1 + len);
+    uint32_t crc = crc32c::Value(&dest_contents()[header_offset+6], 1 + len);
    crc = crc32c::Mask(crc);
-    EncodeFixed32(&dest_.contents_[header_offset], crc);
+    EncodeFixed32(&dest_contents()[header_offset], crc);
  }

  void ForceError() {
-    source_.force_error_ = true;
+    auto src = dynamic_cast<StringSource*>(reader_.file());
+    src->force_error_ = true;
  }

  size_t DroppedBytes() const {
@@ -192,22 +213,25 @@ class LogTest {
  void CheckOffsetPastEndReturnsNoRecords(uint64_t offset_past_end) {
    WriteInitialOffsetLog();
    reading_ = true;
-    source_.contents_ = Slice(dest_.contents_);
-    Reader* offset_reader = new Reader(&source_, &report_, true/*checksum*/,
-                                       WrittenBytes() + offset_past_end);
+    unique_ptr<StringSource> source(new StringSource);
+    source->contents_ = dest_contents();
+    unique_ptr<Reader> offset_reader(
+      new Reader(std::move(source), &report_, true/*checksum*/,
+                 WrittenBytes() + offset_past_end));
    Slice record;
    std::string scratch;
    ASSERT_TRUE(!offset_reader->ReadRecord(&record, &scratch));
-    delete offset_reader;
  }

  void CheckInitialOffsetRecord(uint64_t initial_offset,
                                int expected_record_offset) {
    WriteInitialOffsetLog();
    reading_ = true;
-    source_.contents_ = Slice(dest_.contents_);
-    Reader* offset_reader = new Reader(&source_, &report_, true/*checksum*/,
-                                       initial_offset);
+    unique_ptr<StringSource> source(new StringSource);
+    source->contents_ = dest_contents();
+    unique_ptr<Reader> offset_reader(
+      new Reader(std::move(source), &report_, true/*checksum*/,
+                 initial_offset));
    Slice record;
    std::string scratch;
    ASSERT_TRUE(offset_reader->ReadRecord(&record, &scratch));
@@ -216,7 +240,6 @@ class LogTest {
    ASSERT_EQ(initial_offset_last_record_offsets_[expected_record_offset],
              offset_reader->LastRecordOffset());
    ASSERT_EQ((char)('a' + expected_record_offset), record.data()[0]);
-    delete offset_reader;
  }

 };
@@ -427,13 +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);
 }
@@ -12,8 +12,8 @@
 namespace leveldb {
 namespace log {

-Writer::Writer(WritableFile* dest)
-    : dest_(dest),
+Writer::Writer(unique_ptr<WritableFile>&& dest)
+    : dest_(std::move(dest)),
      block_offset_(0) {
  for (int i = 0; i <= kMaxRecordType; i++) {
    char t = static_cast<char>(i);
@@ -5,6 +5,7 @@
 #ifndef STORAGE_LEVELDB_DB_LOG_WRITER_H_
 #define STORAGE_LEVELDB_DB_LOG_WRITER_H_

+#include <memory>
 #include <stdint.h>
 #include "db/log_format.h"
 #include "leveldb/slice.h"
@@ -14,6 +15,8 @@ namespace leveldb {

 class WritableFile;

+using std::unique_ptr;
+
 namespace log {

 class Writer {
@@ -21,13 +24,16 @@ class Writer {
  // Create a writer that will append data to "*dest".
  // "*dest" must be initially empty.
  // "*dest" must remain live while this Writer is in use.
-  explicit Writer(WritableFile* dest);
+  explicit Writer(unique_ptr<WritableFile>&& dest);
  ~Writer();

  Status AddRecord(const Slice& slice);

+  WritableFile* file() { return dest_.get(); }
+  const WritableFile* file() const { return dest_.get(); }
+
 private:
-  WritableFile* dest_;
+  unique_ptr<WritableFile> dest_;
  int block_offset_;       // Current offset in block

  // crc32c values for all supported record types.  These are
@@ -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 {
@@ -18,21 +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) {
-}
+      edit_(numlevel),
+      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 {
@@ -54,24 +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
@@ -80,7 +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,
@@ -97,7 +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;
@@ -106,14 +120,30 @@ 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_);
+  if (first_seqno_ == 0) {
+    first_seqno_ = s;
+  }
 }

-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;
+  auto logger = options.info_log;
+  std::string merge_result;
+
+  for (; iter->Valid(); iter->Next()) {
    // entry format is:
    //    klength  varint32
    //    userkey  char[klength-8]
@@ -123,7 +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(
@@ -134,15 +164,63 @@ 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->Merge(key.user_key(), &v, *operands,
+                                       value, logger.get())) {
+              *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->Merge(key.user_key(), nullptr, *operands,
+                                       value, logger.get())) {
+              *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;
+        }
      }
+    } 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 <memory>
+#include <deque>
 #include "leveldb/db.h"
 #include "db/dbformat.h"
 #include "db/skiplist.h"
 #include "db/version_set.h"
-#include "util/arena.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_; }
@@ -62,30 +73,39 @@ 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_; }

+  // Returns the sequence number of the first element that was inserted
+  // 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
@@ -96,6 +116,12 @@ class MemTable {
  // memtable is flushed to storage.
  VersionEdit edit_;

+  // 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&);
@@ -43,17 +43,16 @@ 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) {
-    assert(imm_flush_needed.NoBarrier_Load() != NULL);
+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() {
+// Returns the memtables that need to be flushed.
+void MemTableList::PickMemtablesToFlush(std::vector<MemTable*>* ret) {
  for (list<MemTable*>::reverse_iterator it = memlist_.rbegin();
       it != memlist_.rend(); it++) {
    MemTable* m = *it;
@@ -61,40 +60,51 @@ MemTable* MemTableList::PickMemtableToFlush() {
      assert(!m->flush_completed_);
      num_flush_not_started_--;
      if (num_flush_not_started_ == 0) {
-        imm_flush_needed.Release_Store(NULL);
+        imm_flush_needed.Release_Store(nullptr);
      }
      m->flush_in_progress_ = true; // flushing will start very soon
-      return m;
+      ret->push_back(m);
    }
  }
-  return NULL;
 }

 // 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 +116,15 @@ 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 +132,39 @@ 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;
@@ -174,10 +193,13 @@ size_t MemTableList::ApproximateMemoryUsage() {

 // 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) {
+// 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 (list<MemTable*>::iterator it = memlist_.begin();
       it != memlist_.end(); ++it) {
-    if ((*it)->Get(key, value, s)) {
+    if ((*it)->Get(key, value, s, operands, options)) {
      return true;
    }
  }
@@ -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'
@@ -30,11 +30,11 @@ class MemTableList {
  // A list of memtables.
  MemTableList() : size_(0), num_flush_not_started_(0),
    commit_in_progress_(false) {
-    imm_flush_needed.Release_Store(NULL);
+    imm_flush_needed.Release_Store(nullptr);
  }
  ~MemTableList() {};

-  // so that backgrund threads can detect non-NULL pointer to
+  // so that backgrund threads can detect non-nullptr pointer to
  // determine whether this is anything more to start flushing.
  port::AtomicPointer imm_flush_needed;

@@ -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 +1,187 @@
+#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) {
+  // 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_->Merge(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);
+      }
+
+      // 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_->Merge(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);
+      }
+
+      // 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_->Merge(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 {
+      // Do nothing if not success_. Leave keys() and operands() as they are.
+    }
+  }
+}
+
+} // namespace leveldb
@@ -0,0 +1,97 @@
+#ifndef MERGE_HELPER_H
+#define MERGE_HELPER_H
+
+#include "db/dbformat.h"
+#include "leveldb/slice.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);
+
+  // 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::Merge(
+    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 +1,271 @@
+#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;
+
+auto mergeOperator = MergeOperators::CreateUInt64AddOperator();
+
+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 = mergeOperator.get();
+  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;
+}
@@ -50,23 +50,15 @@ class Repairer {
        icmp_(options.comparator),
        ipolicy_(options.filter_policy),
        options_(SanitizeOptions(dbname, &icmp_, &ipolicy_, options)),
-        owns_info_log_(options_.info_log != options.info_log),
-        owns_cache_(options_.block_cache != options.block_cache),
        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);
  }

  ~Repairer() {
    delete table_cache_;
    delete edit_;
-    if (owns_info_log_) {
-      delete options_.info_log;
-    }
-    if (owns_cache_) {
-      delete options_.block_cache;
-    }
  }

  Status Run() {
@@ -104,7 +96,6 @@ class Repairer {
  InternalKeyComparator const icmp_;
  InternalFilterPolicy const ipolicy_;
  Options const options_;
-  bool owns_info_log_;
  bool owns_cache_;
  TableCache* table_cache_;
  VersionEdit* edit_;
@@ -114,6 +105,7 @@ 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;
@@ -164,7 +156,7 @@ class Repairer {
  Status ConvertLogToTable(uint64_t log) {
    struct LogReporter : public log::Reader::Reporter {
      Env* env;
-      Logger* info_log;
+      std::shared_ptr<Logger> info_log;
      uint64_t lognum;
      virtual void Corruption(size_t bytes, const Status& s) {
        // We print error messages for corruption, but continue repairing.
@@ -177,8 +169,8 @@ class Repairer {

    // Open the log file
    std::string logname = LogFileName(dbname_, log);
-    SequentialFile* lfile;
-    Status status = env_->NewSequentialFile(logname, &lfile);
+    unique_ptr<SequentialFile> lfile;
+    Status status = env_->NewSequentialFile(logname, &lfile, storage_options_);
    if (!status.ok()) {
      return status;
    }
@@ -192,14 +184,15 @@ class Repairer {
    // corruptions cause entire commits to be skipped instead of
    // propagating bad information (like overly large sequence
    // numbers).
-    log::Reader reader(lfile, &reporter, false/*do not checksum*/,
+    log::Reader reader(std::move(lfile), &reporter, false/*do not checksum*/,
                       0/*initial_offset*/);

    // Read all the records and add to a memtable
    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)) {
@@ -219,17 +212,18 @@ class Repairer {
        status = Status::OK();  // Keep going with rest of file
      }
    }
-    delete lfile;

    // Do not record a version edit for this conversion to a Table
    // since ExtractMetaData() will also generate edits.
    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();
-    mem = NULL;
+    mem = nullptr;
    if (status.ok()) {
      if (meta.file_size > 0) {
        table_numbers_.push_back(meta.number);
@@ -267,7 +261,7 @@ 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->max_sequence = 0;
@@ -304,8 +298,8 @@ class Repairer {

  Status WriteDescriptor() {
    std::string tmp = TempFileName(dbname_, 1);
-    WritableFile* file;
-    Status status = env_->NewWritableFile(tmp, &file);
+    unique_ptr<WritableFile> file;
+    Status status = env_->NewWritableFile(tmp, &file, storage_options_);
    if (!status.ok()) {
      return status;
    }
@@ -331,16 +325,11 @@ class Repairer {

    //fprintf(stderr, "NewDescriptor:\n%s\n", edit_.DebugString().c_str());
    {
-      log::Writer log(file);
+      log::Writer log(std::move(file));
      std::string record;
      edit_->EncodeTo(&record);
      status = log.AddRecord(record);
    }
-    if (status.ok()) {
-      status = file->Close();
-    }
-    delete file;
-    file = NULL;

    if (!status.ok()) {
      env_->DeleteFile(tmp);
@@ -368,14 +357,14 @@ class Repairer {
    //    dir/lost/foo
    const char* slash = strrchr(fname.c_str(), '/');
    std::string new_dir;
-    if (slash != NULL) {
+    if (slash != nullptr) {
      new_dir.assign(fname.data(), slash - fname.data());
    }
    new_dir.append("/lost");
    env_->CreateDir(new_dir);  // Ignore error
    std::string new_file = new_dir;
    new_file.append("/");
-    new_file.append((slash == NULL) ? fname.c_str() : slash + 1);
+    new_file.append((slash == nullptr) ? fname.c_str() : slash + 1);
    Status s = env_->RenameFile(fname, new_file);
    Log(options_.info_log, "Archiving %s: %s\n",
        fname.c_str(), s.ToString().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:
@@ -127,9 +124,9 @@ class SkipList {
  bool KeyIsAfterNode(const Key& key, Node* n) const;

  // Return the earliest node that comes at or after key.
-  // Return NULL if there is no such node.
+  // Return nullptr if there is no such node.
  //
-  // If prev is non-NULL, fills prev[level] with pointer to previous
+  // If prev is non-nullptr, fills prev[level] with pointer to previous
  // node at "level" for every level in [0..max_height_-1].
  Node* FindGreaterOrEqual(const Key& key, Node** prev) const;

@@ -194,12 +191,12 @@ SkipList<Key,Comparator>::NewNode(const Key& key, int height) {
 template<typename Key, class Comparator>
 inline SkipList<Key,Comparator>::Iterator::Iterator(const SkipList* list) {
  list_ = list;
-  node_ = NULL;
+  node_ = nullptr;
 }

 template<typename Key, class Comparator>
 inline bool SkipList<Key,Comparator>::Iterator::Valid() const {
-  return node_ != NULL;
+  return node_ != nullptr;
 }

 template<typename Key, class Comparator>
@@ -221,13 +218,13 @@ inline void SkipList<Key,Comparator>::Iterator::Prev() {
  assert(Valid());
  node_ = list_->FindLessThan(node_->key);
  if (node_ == list_->head_) {
-    node_ = NULL;
+    node_ = nullptr;
  }
 }

 template<typename Key, class Comparator>
 inline void SkipList<Key,Comparator>::Iterator::Seek(const Key& target) {
-  node_ = list_->FindGreaterOrEqual(target, NULL);
+  node_ = list_->FindGreaterOrEqual(target, nullptr);
 }

 template<typename Key, class Comparator>
@@ -239,7 +236,7 @@ template<typename Key, class Comparator>
 inline void SkipList<Key,Comparator>::Iterator::SeekToLast() {
  node_ = list_->FindLast();
  if (node_ == list_->head_) {
-    node_ = NULL;
+    node_ = nullptr;
  }
 }

@@ -258,8 +255,8 @@ int SkipList<Key,Comparator>::RandomHeight() {

 template<typename Key, class Comparator>
 bool SkipList<Key,Comparator>::KeyIsAfterNode(const Key& key, Node* n) const {
-  // NULL n is considered infinite
-  return (n != NULL) && (compare_(n->key, key) < 0);
+  // nullptr n is considered infinite
+  return (n != nullptr) && (compare_(n->key, key) < 0);
 }

 template<typename Key, class Comparator>
@@ -282,7 +279,7 @@ typename SkipList<Key,Comparator>::Node* SkipList<Key,Comparator>::FindGreaterOr
      // Keep searching in this list
      x = next;
    } else {
-      if (prev != NULL) prev[level] = x;
+      if (prev != nullptr) prev[level] = x;
      if (level == 0) {
        return next;
      } else {
@@ -301,7 +298,7 @@ SkipList<Key,Comparator>::FindLessThan(const Key& key) const {
  while (true) {
    assert(x == head_ || compare_(x->key, key) < 0);
    Node* next = x->Next(level);
-    if (next == NULL || compare_(next->key, key) >= 0) {
+    if (next == nullptr || compare_(next->key, key) >= 0) {
      if (level == 0) {
        return x;
      } else {
@@ -321,7 +318,7 @@ typename SkipList<Key,Comparator>::Node* SkipList<Key,Comparator>::FindLast()
  int level = GetMaxHeight() - 1;
  while (true) {
    Node* next = x->Next(level);
-    if (next == NULL) {
+    if (next == nullptr) {
      if (level == 0) {
        return x;
      } else {
@@ -342,7 +339,7 @@ SkipList<Key,Comparator>::SkipList(Comparator cmp, Arena* arena)
      max_height_(reinterpret_cast<void*>(1)),
      rnd_(0xdeadbeef) {
  for (int i = 0; i < kMaxHeight; i++) {
-    head_->SetNext(i, NULL);
+    head_->SetNext(i, nullptr);
    prev_[i] = head_;
  }
 }
@@ -354,7 +351,7 @@ void SkipList<Key,Comparator>::Insert(const Key& key) {
  Node* x = FindGreaterOrEqual(key, prev_);

  // Our data structure does not allow duplicate insertion
-  assert(x == NULL || !Equal(key, x->key));
+  assert(x == nullptr || !Equal(key, x->key));

  int height = RandomHeight();
  if (height > GetMaxHeight()) {
@@ -366,9 +363,9 @@ void SkipList<Key,Comparator>::Insert(const Key& key) {
    // It is ok to mutate max_height_ without any synchronization
    // with concurrent readers.  A concurrent reader that observes
    // the new value of max_height_ will see either the old value of
-    // new level pointers from head_ (NULL), or a new value set in
+    // new level pointers from head_ (nullptr), or a new value set in
    // the loop below.  In the former case the reader will
-    // immediately drop to the next level since NULL sorts after all
+    // immediately drop to the next level since nullptr sorts after all
    // keys.  In the latter case the reader will use the new node.
    max_height_.NoBarrier_Store(reinterpret_cast<void*>(height));
  }
@@ -385,8 +382,8 @@ void SkipList<Key,Comparator>::Insert(const Key& key) {

 template<typename Key, class Comparator>
 bool SkipList<Key,Comparator>::Contains(const Key& key) const {
-  Node* x = FindGreaterOrEqual(key, NULL);
-  if (x != NULL && Equal(key, x->key)) {
+  Node* x = FindGreaterOrEqual(key, nullptr);
+  if (x != nullptr && Equal(key, x->key)) {
    return true;
  } else {
    return false;
@@ -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"
@@ -14,7 +14,7 @@ namespace leveldb {

 typedef uint64_t Key;

-struct Comparator {
+struct TestComparator {
  int operator()(const Key& a, const Key& b) const {
    if (a < b) {
      return -1;
@@ -29,12 +29,12 @@ struct Comparator {
 class SkipTest { };

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

-  SkipList<Key, Comparator>::Iterator iter(&list);
+  SkipList<Key, TestComparator>::Iterator iter(&list);
  ASSERT_TRUE(!iter.Valid());
  iter.SeekToFirst();
  ASSERT_TRUE(!iter.Valid());
@@ -49,9 +49,9 @@ TEST(SkipTest, InsertAndLookup) {
  const int R = 5000;
  Random rnd(1000);
  std::set<Key> keys;
-  Arena arena;
-  Comparator cmp;
-  SkipList<Key, Comparator> list(cmp, &arena);
+  ArenaImpl arena_impl;
+  TestComparator cmp;
+  SkipList<Key, TestComparator> list(cmp, &arena_impl);
  for (int i = 0; i < N; i++) {
    Key key = rnd.Next() % R;
    if (keys.insert(key).second) {
@@ -69,7 +69,7 @@ TEST(SkipTest, InsertAndLookup) {

  // Simple iterator tests
  {
-    SkipList<Key, Comparator>::Iterator iter(&list);
+    SkipList<Key, TestComparator>::Iterator iter(&list);
    ASSERT_TRUE(!iter.Valid());

    iter.Seek(0);
@@ -87,7 +87,7 @@ TEST(SkipTest, InsertAndLookup) {

  // Forward iteration test
  for (int i = 0; i < R; i++) {
-    SkipList<Key, Comparator>::Iterator iter(&list);
+    SkipList<Key, TestComparator>::Iterator iter(&list);
    iter.Seek(i);

    // Compare against model iterator
@@ -107,7 +107,7 @@ TEST(SkipTest, InsertAndLookup) {

  // Backward iteration test
  {
-    SkipList<Key, Comparator>::Iterator iter(&list);
+    SkipList<Key, TestComparator>::Iterator iter(&list);
    iter.SeekToLast();

    // Compare against model iterator
@@ -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, Comparator> list_;
+  SkipList<Key, TestComparator> list_;

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

  // REQUIRES: External synchronization
  void WriteStep(Random* rnd) {
@@ -230,7 +230,7 @@ class ConcurrentTest {
    }

    Key pos = RandomTarget(rnd);
-    SkipList<Key, Comparator>::Iterator iter(&list_);
+    SkipList<Key, TestComparator>::Iterator iter(&list_);
    iter.Seek(pos);
    while (true) {
      Key current;
@@ -308,7 +308,7 @@ class TestState {

  explicit TestState(int s)
      : seed_(s),
-        quit_flag_(NULL),
+        quit_flag_(nullptr),
        state_(STARTING),
        state_cv_(&mu_) {}

@@ -360,7 +360,7 @@ static void RunConcurrent(int run) {
    for (int i = 0; i < kSize; i++) {
      state.t_.WriteStep(&rnd);
    }
-    state.quit_flag_.Release_Store(&state);  // Any non-NULL arg will do
+    state.quit_flag_.Release_Store(&state);  // Any non-nullptr arg will do
    state.Wait(TestState::DONE);
  }
 }
@@ -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_
@@ -59,18 +59,22 @@ class SnapshotList {

  // retrieve all snapshot numbers. They are sorted in ascending order.
  void getAll(std::vector<SequenceNumber>& ret) {
-    SnapshotImpl* s = &list_;
-    SequenceNumber prev;
-    prev = 0;
    if (empty()) return;
+    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_;
    }
  }

+  // get the sequence number of the most recent snapshot
+  const SequenceNumber GetNewest() {
+    if (empty()) {
+      return 0;
+    }
+    return newest()->number_;
+  }
+
 private:
  // Dummy head of doubly-linked list of snapshots
  SnapshotImpl list_;
@@ -5,26 +5,17 @@
 #include "db/table_cache.h"

 #include "db/filename.h"
-#include "db/db_statistics.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 {
-  RandomAccessFile* file;
-  Table* table;
-};
-
-static class DBStatistics* dbstatistics;
-
 static void DeleteEntry(const Slice& key, void* value) {
-  TableAndFile* tf = reinterpret_cast<TableAndFile*>(value);
-  delete tf->table;
-  delete tf->file;
-  dbstatistics ? dbstatistics->incNumFileCloses() : (void)0;
-  delete tf;
+  Table* table = reinterpret_cast<Table*>(value);
+  delete table;
 }

 static void UnrefEntry(void* arg1, void* arg2) {
@@ -35,75 +26,87 @@ 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 = (DBStatistics*)options->statistics;
-}
+      storage_options_(storage_options),
+      cache_(NewLRUCache(entries, options->table_cache_numshardbits)) {}

 TableCache::~TableCache() {
-  delete cache_;
 }

-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));
-  DBStatistics* stats = (DBStatistics*) options_->statistics;
  *handle = cache_->Lookup(key);
-  if (*handle == NULL) {
-    if (tableIO != NULL) {
-      *tableIO = true;    // we had to do IO from storage
+  if (*handle == nullptr) {
+    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);
-    RandomAccessFile* file = NULL;
-    Table* table = NULL;
-    s = env_->NewRandomAccessFile(fname, &file);
-    stats ? stats->incNumFileOpens() : (void)0;
+    unique_ptr<RandomAccessFile> file;
+    unique_ptr<Table> table;
+    s = env_->NewRandomAccessFile(fname, &file, toptions);
+    RecordTick(options_->statistics, NO_FILE_OPENS);
    if (s.ok()) {
-      s = Table::Open(*options_, 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()) {
-      assert(table == NULL);
-      delete file;
-      stats ? stats->incNumFileErrors() : (void)0;
+      assert(table == nullptr);
+      RecordTick(options_->statistics, NO_FILE_ERRORS);
      // 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->file = file;
-      tf->table = table;
-      *handle = cache_->Insert(key, tf, 1, &DeleteEntry);
+      assert(file.get() == nullptr);
+      *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) {
-  if (tableptr != NULL) {
-    *tableptr = NULL;
+                                  Table** tableptr,
+                                  bool for_compaction) {
+  if (tableptr != nullptr) {
+    *tableptr = nullptr;
  }

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

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

@@ -112,14 +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) {
-  Cache::Handle* handle = NULL;
-  Status s = FindTable(file_number, file_size, &handle, 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(storage_options_, file_number, file_size,
+                       &handle, table_io, no_io);
  if (s.ok()) {
-    Table* t = reinterpret_cast<TableAndFile*>(cache_->Value(handle))->table;
-    s = t->InternalGet(options, k, arg, saver);
+    Table* t =
+      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 {

@@ -20,30 +21,36 @@ 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
  // file length must be exactly "file_size" bytes).  If "tableptr" is
-  // non-NULL, also sets "*tableptr" to point to the Table object
-  // underlying the returned iterator, or NULL if no Table object underlies
+  // non-nullptr, also sets "*tableptr" to point to the Table object
+  // underlying the returned iterator, or nullptr if no Table object underlies
  // the returned iterator.  The returned "*tableptr" object is owned by
  // 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 = NULL);
+                        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_;
-  Cache* cache_;
+  const EnvOptions& storage_options_;
+  std::shared_ptr<Cache> cache_;

-  Status FindTable(uint64_t file_number, uint64_t file_size, Cache::Handle**,
-                   bool* tableIO = NULL);
+  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
@@ -1,49 +1,48 @@
 #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) :
+                           const std::string& dbname,
+                           const Options* options,
+                           const EnvOptions& soptions,
+                           SequenceNumber& seq,
+                           std::unique_ptr<std::vector<LogFile>> files,
+                           SequenceNumber const * const lastFlushedSequence) :
  dbname_(dbname),
  options_(options),
-  sequenceNumber_(seq),
-  files_(files),
+  soptions_(soptions),
+  startingSequenceNumber_(seq),
+  files_(std::move(files)),
  started_(false),
-  isValid_(true),
+  isValid_(false),
  currentFileIndex_(0),
-  currentLogReader_(NULL) {
-  assert( files_ != NULL);
+  lastFlushedSequence_(lastFlushedSequence) {
+  assert(files_.get() != nullptr);
+  assert(lastFlushedSequence_);
+
+  reporter_.env = options_->env;
+  reporter_.info_log = options_->info_log.get();
 }

-LogReporter
-TransactionLogIteratorImpl::NewLogReporter(const uint64_t logNumber) {
-  LogReporter reporter;
-  reporter.env = options_->env;
-  reporter.info_log = options_->info_log;
-  reporter.log_number = logNumber;
-  return reporter;
-}
-
-Status TransactionLogIteratorImpl::OpenLogFile(const LogFile& logFile,
-                                       SequentialFile** file) {
+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);
+    return env->NewSequentialFile(fname, file, soptions_);
  } else {
    std::string fname = LogFileName(dbname_, logFile.logNumber);
-    Status status = env->NewSequentialFile(fname, file);
+    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);
+      status = env->NewSequentialFile(fname, file, soptions_);
      if (!status.ok()) {
-        //  TODO stringprintf
        return Status::IOError(" Requested file not present in the dir");
      }
    }
@@ -51,11 +50,12 @@ Status TransactionLogIteratorImpl::OpenLogFile(const LogFile& logFile,
  }
 }

-void TransactionLogIteratorImpl::GetBatch(WriteBatch* batch,
-                                          SequenceNumber* seq)  {
+BatchResult TransactionLogIteratorImpl::GetBatch()  {
  assert(isValid_);  //  cannot call in a non valid state.
-  WriteBatchInternal::SetContents(batch, currentRecord_);
-  *seq = WriteBatchInternal::Sequence(batch);
+  BatchResult result;
+  result.sequence = currentSequence_;
+  result.writeBatchPtr = std::move(currentBatch_);
+  return result;
 }

 Status TransactionLogIteratorImpl::status() {
@@ -67,82 +67,106 @@ bool TransactionLogIteratorImpl::Valid() {
 }

 void TransactionLogIteratorImpl::Next() {
+  LogFile currentLogFile = files_.get()->at(currentFileIndex_);
+
 //  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_) {
-    SequentialFile* file = NULL;
-    Status status = OpenLogFile(currentLogFile, &file);
-    if (!status.ok()) {
-      isValid_ = false;
-      currentStatus_ = status;
+    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;
    }
-    assert(file != NULL);
-    WriteBatch batch;
-    log::Reader* reader = new log::Reader(file, &reporter, true, 0);
-    assert(reader != NULL);
-    while (reader->ReadRecord(&record, &scratch)) {
-      if (record.size() < 12) {
-        reporter.Corruption(
-          record.size(), Status::Corruption("log record too small"));
-        continue;
-      }
-      WriteBatchInternal::SetContents(&batch, record);
-      SequenceNumber currentNum = WriteBatchInternal::Sequence(&batch);
-      if (currentNum >= sequenceNumber_) {
-        isValid_ = true;
-        currentRecord_ = record;
-        currentLogReader_ = reader;
-        break;
-      }
+    Status s = OpenLogReader(currentLogFile);
+    if (!s.ok()) {
+      currentStatus_ = s;
+      isValid_ = false;
+      return;
    }
-    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_ != NULL);
-    bool openNextFile = true;
    while (currentLogReader_->ReadRecord(&record, &scratch)) {
      if (record.size() < 12) {
-        reporter.Corruption(
+        reporter_.Corruption(
          record.size(), Status::Corruption("log record too small"));
        continue;
-      } else {
-        currentRecord_ = record;
-        openNextFile = false;
+      }
+      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_->size() - 1) {
+      if (currentFileIndex_ < files_.get()->size() - 1) {
        ++currentFileIndex_;
-        delete currentLogReader_;
-        SequentialFile *file;
-        Status status = OpenLogFile(files_->at(currentFileIndex_), &file);
+        Status status = OpenLogReader(files_.get()->at(currentFileIndex_));
        if (!status.ok()) {
          isValid_ = false;
          currentStatus_ = status;
          return;
        }
-        currentLogReader_ = new log::Reader(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");
+        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
@@ -16,26 +16,19 @@ 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 TransactionLogIteratorImpl : public TransactionLogIterator {
 public:
  TransactionLogIteratorImpl(const std::string& dbname,
-                     const Options* options,
-                     SequenceNumber& seqNum,
-                     std::vector<LogFile>* files);
-  virtual ~TransactionLogIteratorImpl() {
-    //  TODO move to cc file.
-    if (currentLogReader_ != NULL) {
-      delete currentLogReader_;
-    }
-    delete files_;
-  }
+                             const Options* options,
+                             const EnvOptions& soptions,
+                             SequenceNumber& seqNum,
+                             std::unique_ptr<std::vector<LogFile>> files,
+                             SequenceNumber const * const lastFlushedSequence);

  virtual bool Valid();

@@ -43,21 +36,28 @@ class TransactionLogIteratorImpl : public TransactionLogIterator {

  virtual Status status();

-  virtual void GetBatch(WriteBatch* batch, SequenceNumber* seq);
+  virtual BatchResult GetBatch();

 private:
  const std::string& dbname_;
  const Options* options_;
-  const uint64_t sequenceNumber_;
-  const std::vector<LogFile>* files_;
+  const EnvOptions& soptions_;
+  const uint64_t startingSequenceNumber_;
+  std::unique_ptr<std::vector<LogFile>> files_;
  bool started_;
  bool isValid_;  // not valid when it starts of.
  Status currentStatus_;
  size_t currentFileIndex_;
-  Slice currentRecord_;
-  log::Reader* currentLogReader_;
-  Status OpenLogFile(const LogFile& logFile, SequentialFile** file);
-  LogReporter NewLogReporter(uint64_t logNumber);
+  std::unique_ptr<WriteBatch> currentBatch_;
+  unique_ptr<log::Reader> currentLogReader_;
+  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);
 };


@@ -95,13 +95,16 @@ static bool GetInternalKey(Slice* input, InternalKey* dst) {
  }
 }

-bool VersionEdit::GetLevel(Slice* input, int* level) {
+bool VersionEdit::GetLevel(Slice* input, int* level, const char** msg) {
  uint32_t v;
  if (GetVarint32(input, &v) &&
      (int)v < number_levels_) {
    *level = v;
    return true;
  } else {
+    if ((int)v >= number_levels_) {
+      *msg = "db already has more levels than options.num_levels";
+    }
    return false;
  }
 }
@@ -109,7 +112,7 @@ bool VersionEdit::GetLevel(Slice* input, int* level) {
 Status VersionEdit::DecodeFrom(const Slice& src) {
  Clear();
  Slice input = src;
-  const char* msg = NULL;
+  const char* msg = nullptr;
  uint32_t tag;

  // Temporary storage for parsing
@@ -119,7 +122,7 @@ Status VersionEdit::DecodeFrom(const Slice& src) {
  Slice str;
  InternalKey key;

-  while (msg == NULL && GetVarint32(&input, &tag)) {
+  while (msg == nullptr && GetVarint32(&input, &tag)) {
    switch (tag) {
      case kComparator:
        if (GetLengthPrefixedSlice(&input, &str)) {
@@ -163,32 +166,38 @@ Status VersionEdit::DecodeFrom(const Slice& src) {
        break;

      case kCompactPointer:
-        if (GetLevel(&input, &level) &&
+        if (GetLevel(&input, &level, &msg) &&
            GetInternalKey(&input, &key)) {
          compact_pointers_.push_back(std::make_pair(level, key));
        } else {
-          msg = "compaction pointer";
+          if (!msg) {
+            msg = "compaction pointer";
+          }
        }
        break;

      case kDeletedFile:
-        if (GetLevel(&input, &level) &&
+        if (GetLevel(&input, &level, &msg) &&
            GetVarint64(&input, &number)) {
          deleted_files_.insert(std::make_pair(level, number));
        } else {
-          msg = "deleted file";
+          if (!msg) {
+            msg = "deleted file";
+          }
        }
        break;

      case kNewFile:
-        if (GetLevel(&input, &level) &&
+        if (GetLevel(&input, &level, &msg) &&
            GetVarint64(&input, &f.number) &&
            GetVarint64(&input, &f.file_size) &&
            GetInternalKey(&input, &f.smallest) &&
            GetInternalKey(&input, &f.largest)) {
          new_files_.push_back(std::make_pair(level, f));
        } else {
-          msg = "new-file entry";
+          if (!msg) {
+            msg = "new-file entry";
+          }
        }
        break;

@@ -198,12 +207,12 @@ Status VersionEdit::DecodeFrom(const Slice& src) {
    }
  }

-  if (msg == NULL && !input.empty()) {
+  if (msg == nullptr && !input.empty()) {
    msg = "invalid tag";
  }

  Status result;
-  if (msg != NULL) {
+  if (msg != nullptr) {
    result = Status::Corruption("VersionEdit", msg);
  }
  return result;
@@ -81,6 +81,11 @@ 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);

@@ -91,7 +96,7 @@ class VersionEdit {

  typedef std::set< std::pair<int, uint64_t> > DeletedFileSet;

-  bool GetLevel(Slice* input, int* level);
+  bool GetLevel(Slice* input, int* level, const char** msg);

  int number_levels_;
  std::string comparator_;
@@ -16,6 +16,7 @@
 #define STORAGE_LEVELDB_DB_VERSION_SET_H_

 #include <map>
+#include <memory>
 #include <set>
 #include <vector>
 #include <deque>
@@ -46,8 +47,8 @@ extern int FindFile(const InternalKeyComparator& icmp,

 // Returns true iff some file in "files" overlaps the user key range
 // [*smallest,*largest].
-// smallest==NULL represents a key smaller than all keys in the DB.
-// largest==NULL represents a key largest than all keys in the DB.
+// smallest==nullptr represents a key smaller than all keys in the DB.
+// largest==nullptr represents a key largest than all keys in the DB.
 // REQUIRES: If disjoint_sorted_files, files[] contains disjoint ranges
 //           in sorted order.
 extern bool SomeFileOverlapsRange(
@@ -62,17 +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.
@@ -86,26 +91,26 @@ class Version {

  void GetOverlappingInputs(
      int level,
-      const InternalKey* begin,         // NULL means before all keys
-      const InternalKey* end,           // NULL means after all keys
+      const InternalKey* begin,         // nullptr means before all keys
+      const InternalKey* end,           // nullptr means after all keys
      std::vector<FileMetaData*>* inputs,
      int hint_index = -1,              // index of overlap file
-      int* file_index = NULL);          // return index of overlap file
+      int* file_index = nullptr);          // return index of overlap file

  void GetOverlappingInputsBinarySearch(
      int level,
-      const Slice& begin,         // NULL means before all keys
-      const Slice& end,           // NULL means after all keys
+      const Slice& begin,         // nullptr means before all keys
+      const Slice& end,           // nullptr means after all keys
      std::vector<FileMetaData*>* inputs,
      int hint_index,             // index of overlap file
      int* file_index);           // return index of overlap file

  void ExtendOverlappingInputs(
      int level,
-      const Slice& begin,         // NULL means before all keys
-      const Slice& end,           // NULL means after all keys
+      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].
@@ -115,6 +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,
@@ -133,9 +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
@@ -175,6 +191,7 @@ class Version {
  std::vector<double> compaction_score_;
  std::vector<int> compaction_level_;
  double max_compaction_score_; // max score in l1 to ln-1
+  int max_compaction_score_level_; // level on which max score occurs

  // The offset in the manifest file where this version is stored.
  uint64_t offset_manifest_file_;
@@ -202,6 +219,7 @@ class VersionSet {
 public:
  VersionSet(const std::string& dbname,
             const Options* options,
+             const EnvOptions& storage_options,
             TableCache* table_cache,
             const InternalKeyComparator*);
  ~VersionSet();
@@ -271,13 +289,13 @@ class VersionSet {
  int NumberLevels() const { return num_levels_; }

  // Pick level and inputs for a new compaction.
-  // Returns NULL if there is no compaction to be done.
+  // Returns nullptr if there is no compaction to be done.
  // Otherwise returns a pointer to a heap-allocated object that
  // describes the compaction.  Caller should delete the result.
  Compaction* PickCompaction();

  // Return a compaction object for compacting the range [begin,end] in
-  // the specified level.  Returns NULL if there is nothing in that
+  // the specified level.  Returns nullptr if there is nothing in that
  // level that overlaps the specified range.  Caller should delete
  // the result.
  Compaction* CompactRange(
@@ -305,7 +323,7 @@ class VersionSet {
  }
  // Returns true iff some level needs a compaction.
  bool NeedsCompaction() const {
-    return ((current_->file_to_compact_ != NULL) ||
+    return ((current_->file_to_compact_ != nullptr) ||
            NeedsSizeCompaction());
  }

@@ -314,9 +332,13 @@ class VersionSet {
    return current_->max_compaction_score_;
  }

+  // See field declaration
+  int MaxCompactionScoreLevel() const {
+    return current_->max_compaction_score_level_;
+  }
+
  // 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);
@@ -344,7 +366,9 @@ class VersionSet {
  const uint64_t ManifestFileSize() { return current_->offset_manifest_file_; }

  // For the specfied level, pick a compaction.
-  // Returns NULL if there is no compaction to be done.
+  // Returns nullptr if there is no compaction to be done.
+  // If level is 0 and there is already a compaction on that level, this
+  // function will return nullptr.
  Compaction* PickCompactionBySize(int level, double score);

  // Free up the files that were participated in a compaction
@@ -366,6 +390,11 @@ class VersionSet {
  // record results in files_by_size_. The largest files are listed first.
  void UpdateFilesBySize(Version *v);

+  // Get the max file size in a given level.
+  uint64_t MaxFileSizeForLevel(int level);
+
+  double MaxBytesForLevel(int level);
+
 private:
  class Builder;
  struct ManifestWriter;
@@ -375,7 +404,7 @@ class VersionSet {

  void Init(int num_levels);

-  void Finalize(Version* v);
+  void Finalize(Version* v, std::vector<uint64_t>&);

  void GetRange(const std::vector<FileMetaData*>& inputs,
                InternalKey* smallest,
@@ -386,6 +415,8 @@ class VersionSet {
                 InternalKey* smallest,
                 InternalKey* largest);

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

  // Save current contents to *log
@@ -393,9 +424,7 @@ class VersionSet {

  void AppendVersion(Version* v);

-  double MaxBytesForLevel(int level);
-
-  uint64_t MaxFileSizeForLevel(int level);
+  bool ManifestContains(const std::string& record) const;

  int64_t ExpandedCompactionByteSizeLimit(int level);

@@ -415,8 +444,7 @@ class VersionSet {
  int num_levels_;

  // Opened lazily
-  WritableFile* descriptor_file_;
-  log::Writer* descriptor_log_;
+  unique_ptr<log::Writer> descriptor_log_;
  Version dummy_versions_;  // Head of circular doubly-linked list of versions.
  Version* current_;        // == dummy_versions_.prev_

@@ -439,13 +467,24 @@ class VersionSet {
  // Queue of writers to the manifest file
  std::deque<ManifestWriter*> manifest_writers_;

+  // Store the manifest file size when it is checked.
+  // 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&);

  // Return the total amount of data that is undergoing
-  // compactions at this level
-  uint64_t SizeBeingCompacted(int level);
+  // compactions per level
+  void SizeBeingCompacted(std::vector<uint64_t>&);

  // Returns true if any one of the parent files are being compacted
  bool ParentRangeInCompaction(const InternalKey* smallest,
@@ -542,7 +581,7 @@ class Compaction {
  // 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);
@@ -67,7 +67,8 @@ Status VersionSet::ReduceNumberOfLevels(int new_levels, port::Mutex* mu) {
  num_levels_ = new_levels;
  compact_pointer_ = new std::string[new_levels];
  Init(new_levels);
-  st = LogAndApply(new VersionEdit(new_levels), mu, true);
+  VersionEdit ve(new_levels);
+  st = LogAndApply(&ve , mu, true);
  return st;
 }

@@ -40,20 +40,20 @@ class FindFileTest {

  bool Overlaps(const char* smallest, const char* largest) {
    InternalKeyComparator cmp(BytewiseComparator());
-    Slice s(smallest != NULL ? smallest : "");
-    Slice l(largest != NULL ? largest : "");
+    Slice s(smallest != nullptr ? smallest : "");
+    Slice l(largest != nullptr ? largest : "");
    return SomeFileOverlapsRange(cmp, disjoint_sorted_files_, files_,
-                                 (smallest != NULL ? &s : NULL),
-                                 (largest != NULL ? &l : NULL));
+                                 (smallest != nullptr ? &s : nullptr),
+                                 (largest != nullptr ? &l : nullptr));
  }
 };

 TEST(FindFileTest, Empty) {
  ASSERT_EQ(0, Find("foo"));
  ASSERT_TRUE(! Overlaps("a", "z"));
-  ASSERT_TRUE(! Overlaps(NULL, "z"));
-  ASSERT_TRUE(! Overlaps("a", NULL));
-  ASSERT_TRUE(! Overlaps(NULL, NULL));
+  ASSERT_TRUE(! Overlaps(nullptr, "z"));
+  ASSERT_TRUE(! Overlaps("a", nullptr));
+  ASSERT_TRUE(! Overlaps(nullptr, nullptr));
 }

 TEST(FindFileTest, Single) {
@@ -78,12 +78,12 @@ TEST(FindFileTest, Single) {
  ASSERT_TRUE(Overlaps("q", "q"));
  ASSERT_TRUE(Overlaps("q", "q1"));

-  ASSERT_TRUE(! Overlaps(NULL, "j"));
-  ASSERT_TRUE(! Overlaps("r", NULL));
-  ASSERT_TRUE(Overlaps(NULL, "p"));
-  ASSERT_TRUE(Overlaps(NULL, "p1"));
-  ASSERT_TRUE(Overlaps("q", NULL));
-  ASSERT_TRUE(Overlaps(NULL, NULL));
+  ASSERT_TRUE(! Overlaps(nullptr, "j"));
+  ASSERT_TRUE(! Overlaps("r", nullptr));
+  ASSERT_TRUE(Overlaps(nullptr, "p"));
+  ASSERT_TRUE(Overlaps(nullptr, "p1"));
+  ASSERT_TRUE(Overlaps("q", nullptr));
+  ASSERT_TRUE(Overlaps(nullptr, nullptr));
 }


@@ -130,19 +130,19 @@ TEST(FindFileTest, MultipleNullBoundaries) {
  Add("200", "250");
  Add("300", "350");
  Add("400", "450");
-  ASSERT_TRUE(! Overlaps(NULL, "149"));
-  ASSERT_TRUE(! Overlaps("451", NULL));
-  ASSERT_TRUE(Overlaps(NULL, NULL));
-  ASSERT_TRUE(Overlaps(NULL, "150"));
-  ASSERT_TRUE(Overlaps(NULL, "199"));
-  ASSERT_TRUE(Overlaps(NULL, "200"));
-  ASSERT_TRUE(Overlaps(NULL, "201"));
-  ASSERT_TRUE(Overlaps(NULL, "400"));
-  ASSERT_TRUE(Overlaps(NULL, "800"));
-  ASSERT_TRUE(Overlaps("100", NULL));
-  ASSERT_TRUE(Overlaps("200", NULL));
-  ASSERT_TRUE(Overlaps("449", NULL));
-  ASSERT_TRUE(Overlaps("450", NULL));
+  ASSERT_TRUE(! Overlaps(nullptr, "149"));
+  ASSERT_TRUE(! Overlaps("451", nullptr));
+  ASSERT_TRUE(Overlaps(nullptr, nullptr));
+  ASSERT_TRUE(Overlaps(nullptr, "150"));
+  ASSERT_TRUE(Overlaps(nullptr, "199"));
+  ASSERT_TRUE(Overlaps(nullptr, "200"));
+  ASSERT_TRUE(Overlaps(nullptr, "201"));
+  ASSERT_TRUE(Overlaps(nullptr, "400"));
+  ASSERT_TRUE(Overlaps(nullptr, "800"));
+  ASSERT_TRUE(Overlaps("100", nullptr));
+  ASSERT_TRUE(Overlaps("200", nullptr));
+  ASSERT_TRUE(Overlaps("449", nullptr));
+  ASSERT_TRUE(Overlaps("450", nullptr));
 }

 TEST(FindFileTest, OverlapSequenceChecks) {
@@ -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 +39,19 @@ 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::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) {
@@ -68,6 +81,14 @@ Status WriteBatch::Iterate(Handler* handler) const {
          return Status::Corruption("bad WriteBatch Delete");
        }
        break;
+      case kTypeMerge:
+        if (GetLengthPrefixedSlice(&input, &key) &&
+            GetLengthPrefixedSlice(&input, &value)) {
+          handler->Merge(key, value);
+        } else {
+          return Status::Corruption("bad WriteBatch Merge");
+        }
+        break;
      default:
        return Status::Corruption("unknown WriteBatch tag");
    }
@@ -108,28 +129,68 @@ 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);
+}
+
+
 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);
@@ -33,6 +36,14 @@ 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());
@@ -59,6 +70,7 @@ 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 +85,7 @@ TEST(WriteBatchTest, Multiple) {
            "Delete(box)@101"
            "Put(foo, bar)@100",
            PrintContents(&batch));
+  ASSERT_EQ(3, batch.Count());
 }

 TEST(WriteBatchTest, Corruption) {
@@ -95,16 +108,19 @@ 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 +128,7 @@ TEST(WriteBatchTest, Append) {
            "Put(b, vb)@201"
            "Delete(foo)@203",
            PrintContents(&b1));
+  ASSERT_EQ(4, b1.Count());
 }

 }  // namespace leveldb
@@ -0,0 +1,2 @@
+ar: creating libmemenv.a
+ar: creating libleveldb.a
@@ -0,0 +1,50 @@
+#!/bin/sh
+#
+# Set environment variables so that we can compile leveldb using
+# fbcode settings.  It uses the latest g++ compiler and also
+# uses jemalloc
+
+TOOLCHAIN_REV=f365dbeae46a30414a2874a6f45e73e10f1caf7d
+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
+GLIBC_RUNTIME_PATH=/usr/local/fbcode/gcc-4.7.1-glibc-2.14.1
+
+# location of snappy headers and libraries
+SNAPPY_INCLUDE=" -I $TOOLCHAIN_LIB_BASE/snappy/snappy-1.0.3/7518bbe/include"
+SNAPPY_LIBS=" $TOOLCHAIN_LIB_BASE/snappy/snappy-1.0.3/7518bbe/lib/libsnappy.a"
+
+# location of boost headers and libraries
+THRIFT_INCLUDE=" -I $TOOLCHAIN_LIB_BASE/boost/boost-1.48.0/bef9365/include -std=gnu++0x"
+THRIFT_INCLUDE+=" -I./thrift -I./thrift/gen-cpp -I./thrift/lib/cpp"
+THRIFT_LIBS=" -L $TOOLCHAIN_LIB_BASE/boost/boost-1.48.0/bef9365/lib"
+
+# location of libevent
+LIBEVENT_INCLUDE=" -I $TOOLCHAIN_LIB_BASE/libevent/libevent-1.4.14b/91ddd43/include"
+LIBEVENT_LIBS=" -L $TOOLCHAIN_LIB_BASE/libevent/libevent-1.4.14b/91ddd43/lib"
+
+# use Intel SSE support for checksum calculations
+export USE_SSE=" -msse -msse4.2 "
+
+CC="$TOOLCHAIN_EXECUTABLES/clang/clang-3.1/6ca8a59/bin/clang $CLANG_INCLUDES"
+CXX="$TOOLCHAIN_EXECUTABLES/clang/clang-3.1/6ca8a59/bin/clang++ $CLANG_INCLUDES $JINCLUDE $SNAPPY_INCLUDE $THRIFT_INCLUDE $LIBEVENT_INCLUDE"
+AR=$TOOLCHAIN_EXECUTABLES/binutils/binutils-2.21.1/da39a3e/bin/ar
+RANLIB=$TOOLCHAIN_EXECUTABLES/binutils/binutils-2.21.1/da39a3e/bin/ranlib
+
+CFLAGS="-B$TOOLCHAIN_EXECUTABLES/binutils/binutils-2.21.1/da39a3e/bin -nostdlib -nostdinc -isystem $TOOLCHAIN_LIB_BASE/libgcc/libgcc-4.7.1/afc21dc/include/c++/4.7.1 -isystem $TOOLCHAIN_LIB_BASE/libgcc/libgcc-4.7.1/afc21dc/include/c++/4.7.1/x86_64-facebook-linux -isystem $TOOLCHAIN_LIB_BASE/libgcc/libgcc-4.7.1/afc21dc/include/c++/4.7.1/backward -isystem $TOOLCHAIN_LIB_BASE/glibc/glibc-2.14.1/99df8fc/include -isystem $TOOLCHAIN_LIB_BASE/clang/clang-3.1/c8f7279/lib/clang/3.1/include -isystem $TOOLCHAIN_LIB_BASE/kernel-headers/kernel-headers-3.2.18_70_fbk11_00129_gc8882d0/da39a3e/include/linux -isystem $TOOLCHAIN_LIB_BASE/kernel-headers/kernel-headers-3.2.18_70_fbk11_00129_gc8882d0/da39a3e/include -Wall -Wno-sign-compare -Wno-unused-variable -Winvalid-pch -Wno-deprecated -Woverloaded-virtual"
+CXXFLAGS="$CFLAGS -nostdinc++ -std=gnu++0x"
+
+CFLAGS+=" -I $TOOLCHAIN_LIB_BASE/jemalloc/$TOOL_JEMALLOC/include -DHAVE_JEMALLOC"
+
+EXEC_LDFLAGS=" -Wl,--whole-archive $TOOLCHAIN_LIB_BASE/jemalloc/$TOOL_JEMALLOC/lib/libjemalloc.a"
+EXEC_LDFLAGS+=" -Wl,--no-whole-archive $TOOLCHAIN_LIB_BASE/libunwind/libunwind-1.0.1/91ddd43/lib/libunwind.a"
+EXEC_LDFLAGS+=" $HDFSLIB $SNAPPY_LIBS $THRIFT_LIBS $LIBEVENT_LIBS"
+EXEC_LDFLAGS+=" -Wl,--dynamic-linker,$GLIBC_RUNTIME_PATH/lib/ld-linux-x86-64.so.2"
+EXEC_LDFLAGS+=" -B$TOOLCHAIN_EXECUTABLES/binutils/binutils-2.21.1/da39a3e/bin"
+
+PLATFORM_LDFLAGS="-L$TOOLCHAIN_LIB_BASE/libgcc/libgcc-4.7.1/afc21dc/lib -L$TOOLCHAIN_LIB_BASE/glibc/glibc-2.14.1/99df8fc/lib"
+
+EXEC_LDFLAGS_SHARED="$SNAPPY_LIBS"
+SNAPPY_LDFLAGS="$SNAPPY_LIBS"
+
+export CC CXX AR RANLIB CFLAGS EXEC_LDFLAGS EXEC_LDFLAGS_SHARED SNAPPY_LDFLAGS
@@ -3,12 +3,11 @@
 # Set environment variables so that we can compile leveldb using
 # fbcode settings.  It uses the latest g++ compiler and also
 # uses jemalloc
-# This is compiled with gcc version 4.7.1 for zeus proxy

-TOOLCHAIN_REV=20d3328ac30f633840ce819ad03019f415267a86
+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-3.0.0/69dc57c
+TOOL_JEMALLOC=jemalloc-3.3.1/2f45f3a

 # location of libhdfs libraries
 if test "$USE_HDFS"; then
@@ -24,10 +23,14 @@ fi
 SNAPPY_INCLUDE=" -I $TOOLCHAIN_LIB_BASE/snappy/snappy-1.0.3/7518bbe/include"
 SNAPPY_LIBS=" $TOOLCHAIN_LIB_BASE/snappy/snappy-1.0.3/7518bbe/lib/libsnappy.a"

+# location of zlib headers and libraries
+ZLIB_INCLUDE=" -I $TOOLCHAIN_LIB_BASE/zlib/zlib-1.2.5/91ddd43/include"
+ZLIB_LIBS=" $TOOLCHAIN_LIB_BASE/zlib/zlib-1.2.5/91ddd43/lib/libz.a"
+
 # location of boost headers and libraries
-THRIFT_INCLUDE=" -I $TOOLCHAIN_LIB_BASE/boost/boost-1.48.0/bef9365/include -std=gnu++0x"
+THRIFT_INCLUDE=" -I $TOOLCHAIN_LIB_BASE/boost/boost-1.48.0/2a0840d/include"
 THRIFT_INCLUDE+=" -I./thrift -I./thrift/gen-cpp -I./thrift/lib/cpp"
-THRIFT_LIBS=" -L $TOOLCHAIN_LIB_BASE/boost/boost-1.48.0/bef9365/lib"
+THRIFT_LIBS=" -L $TOOLCHAIN_LIB_BASE/boost/boost-1.48.0/2a0840d/lib"

 # location of libevent
 LIBEVENT_INCLUDE=" -I $TOOLCHAIN_LIB_BASE/libevent/libevent-1.4.14b/91ddd43/include"
@@ -37,7 +40,7 @@ LIBEVENT_LIBS=" -L $TOOLCHAIN_LIB_BASE/libevent/libevent-1.4.14b/91ddd43/lib"
 export USE_SSE=" -msse -msse4.2 "

 CC="$TOOLCHAIN_EXECUTABLES/gcc/gcc-4.7.1-glibc-2.14.1/bin/gcc"
-CXX="$TOOLCHAIN_EXECUTABLES/gcc/gcc-4.7.1-glibc-2.14.1/bin/g++ $JINCLUDE $SNAPPY_INCLUDE $THRIFT_INCLUDE $LIBEVENT_INCLUDE"
+CXX="$TOOLCHAIN_EXECUTABLES/gcc/gcc-4.7.1-glibc-2.14.1/bin/g++ $JINCLUDE $SNAPPY_INCLUDE $ZLIB_INCLUDE $THRIFT_INCLUDE $LIBEVENT_INCLUDE"
 AR=$TOOLCHAIN_EXECUTABLES/binutils/binutils-2.21.1/da39a3e/bin/ar
 RANLIB=$TOOLCHAIN_EXECUTABLES/binutils/binutils-2.21.1/da39a3e/bin/ranlib

@@ -45,9 +48,14 @@ CFLAGS="-B$TOOLCHAIN_EXECUTABLES/binutils/binutils-2.21.1/bin/gold -m64 -mtune=g
 CFLAGS+=" -I $TOOLCHAIN_LIB_BASE/jemalloc/$TOOL_JEMALLOC/include -DHAVE_JEMALLOC"

 EXEC_LDFLAGS=" -Wl,--whole-archive $TOOLCHAIN_LIB_BASE/jemalloc/$TOOL_JEMALLOC/lib/libjemalloc.a"
-EXEC_LDFLAGS+=" -Wl,--no-whole-archive $TOOLCHAIN_LIB_BASE/libunwind/libunwind-20100812_experimental/91ddd43/lib/libunwind.a"
-EXEC_LDFLAGS+=" $HDFSLIB $SNAPPY_LIBS $THRIFT_LIBS $LIBEVENT_LIBS"
-EXEC_LDFLAGS_SHARED="$SNAPPY_LIBS $TOOLCHAIN_LIB_BASE/jemalloc/$TOOL_JEMALLOC/lib/libjemalloc.so"
-SNAPPY_LDFLAGS="$SNAPPY_LIBS"
+EXEC_LDFLAGS+=" -Wl,--no-whole-archive $TOOLCHAIN_LIB_BASE/libunwind/libunwind-1.0.1/91ddd43/lib/libunwind.a"
+EXEC_LDFLAGS+=" $HDFSLIB $SNAPPY_LIBS $ZLIB_LIBS $THRIFT_LIBS $LIBEVENT_LIBS"

-export CC CXX AR RANLIB CFLAGS EXEC_LDFLAGS EXEC_LDFLAGS_SHARED SNAPPY_LDFLAGS
+PLATFORM_LDFLAGS="-L$TOOLCHAIN_LIB_BASE/libgcc/libgcc-4.7.1/afc21dc/lib -L$TOOLCHAIN_LIB_BASE/glibc/glibc-2.14.1/99df8fc/lib"
+
+EXEC_LDFLAGS_SHARED="$SNAPPY_LIBS $ZLIB_LIBS"
+SNAPPY_LDFLAGS="$SNAPPY_LIBS $ZLIB_LIBS"
+
+VALGRIND_VER="$TOOLCHAIN_LIB_BASE/valgrind/valgrind-3.8.1/91ddd43/bin/"
+
+export CC CXX AR RANLIB CFLAGS EXEC_LDFLAGS EXEC_LDFLAGS_SHARED SNAPPY_LDFLAGS VALGRIND_VER
@@ -235,13 +235,20 @@ class HdfsEnv : public Env {
  }

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

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

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

  virtual bool FileExists(const std::string& fname){return false;}

@@ -269,7 +276,8 @@ class HdfsEnv : public Env {

  virtual Status UnlockFile(FileLock* lock){return notsup;}

-  virtual Status NewLogger(const std::string& fname, Logger** result){return notsup;}
+  virtual Status NewLogger(const std::string& fname,
+                           shared_ptr<Logger>* result){return notsup;}

  virtual void Schedule( void (*function)(void* arg), void* arg) {}

@@ -233,31 +233,34 @@ class InMemoryEnv : public EnvWrapper {

  // Partial implementation of the Env interface.
  virtual Status NewSequentialFile(const std::string& fname,
-                                   SequentialFile** result) {
+                                   unique_ptr<SequentialFile>* result,
+                                   const EnvOptions& soptions) {
    MutexLock lock(&mutex_);
    if (file_map_.find(fname) == file_map_.end()) {
      *result = NULL;
      return Status::IOError(fname, "File not found");
    }

-    *result = new SequentialFileImpl(file_map_[fname]);
+    result->reset(new SequentialFileImpl(file_map_[fname]));
    return Status::OK();
  }

  virtual Status NewRandomAccessFile(const std::string& fname,
-                                     RandomAccessFile** result) {
+                                     unique_ptr<RandomAccessFile>* result,
+                                     const EnvOptions& soptions) {
    MutexLock lock(&mutex_);
    if (file_map_.find(fname) == file_map_.end()) {
      *result = NULL;
      return Status::IOError(fname, "File not found");
    }

-    *result = new RandomAccessFileImpl(file_map_[fname]);
+    result->reset(new RandomAccessFileImpl(file_map_[fname]));
    return Status::OK();
  }

  virtual Status NewWritableFile(const std::string& fname,
-                                 WritableFile** result) {
+                                 unique_ptr<WritableFile>* result,
+                                 const EnvOptions& soptions) {
    MutexLock lock(&mutex_);
    if (file_map_.find(fname) != file_map_.end()) {
      DeleteFileInternal(fname);
@@ -267,7 +270,7 @@ class InMemoryEnv : public EnvWrapper {
    file->Ref();
    file_map_[fname] = file;

-    *result = new WritableFileImpl(file);
+    result->reset(new WritableFileImpl(file));
    return Status::OK();
  }

@@ -8,6 +8,7 @@
 #include "leveldb/db.h"
 #include "leveldb/env.h"
 #include "util/testharness.h"
+#include <memory>
 #include <string>
 #include <vector>

@@ -16,6 +17,7 @@ namespace leveldb {
 class MemEnvTest {
 public:
  Env* env_;
+  const EnvOptions soptions_;

  MemEnvTest()
      : env_(NewMemEnv(Env::Default())) {
@@ -27,7 +29,7 @@ class MemEnvTest {

 TEST(MemEnvTest, Basics) {
  uint64_t file_size;
-  WritableFile* writable_file;
+  unique_ptr<WritableFile> writable_file;
  std::vector<std::string> children;

  ASSERT_OK(env_->CreateDir("/dir"));
@@ -39,8 +41,8 @@ TEST(MemEnvTest, Basics) {
  ASSERT_EQ(0U, children.size());

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

  // Check that the file exists.
  ASSERT_TRUE(env_->FileExists("/dir/f"));
@@ -51,9 +53,9 @@ 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"));
-  delete writable_file;
+  writable_file.reset();

  // Check for expected size.
  ASSERT_OK(env_->GetFileSize("/dir/f", &file_size));
@@ -68,11 +70,13 @@ TEST(MemEnvTest, Basics) {
  ASSERT_EQ(3U, file_size);

  // Check that opening non-existent file fails.
-  SequentialFile* seq_file;
-  RandomAccessFile* rand_file;
-  ASSERT_TRUE(!env_->NewSequentialFile("/dir/non_existent", &seq_file).ok());
+  unique_ptr<SequentialFile> seq_file;
+  unique_ptr<RandomAccessFile> rand_file;
+  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.
@@ -85,21 +89,21 @@ TEST(MemEnvTest, Basics) {
 }

 TEST(MemEnvTest, ReadWrite) {
-  WritableFile* writable_file;
-  SequentialFile* seq_file;
-  RandomAccessFile* rand_file;
+  unique_ptr<WritableFile> writable_file;
+  unique_ptr<SequentialFile> seq_file;
+  unique_ptr<RandomAccessFile> rand_file;
  Slice result;
  char scratch[100];

  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"));
-  delete writable_file;
+  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));
@@ -110,10 +114,9 @@ TEST(MemEnvTest, ReadWrite) {
  ASSERT_OK(seq_file->Skip(100)); // Try to skip past end of file.
  ASSERT_OK(seq_file->Read(1000, &result, scratch));
  ASSERT_EQ(0U, result.size());
-  delete seq_file;

  // 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".
@@ -123,7 +126,6 @@ TEST(MemEnvTest, ReadWrite) {

  // Too high offset.
  ASSERT_TRUE(!rand_file->Read(1000, 5, &result, scratch).ok());
-  delete rand_file;
 }

 TEST(MemEnvTest, Locks) {
@@ -139,14 +141,14 @@ TEST(MemEnvTest, Misc) {
  ASSERT_OK(env_->GetTestDirectory(&test_dir));
  ASSERT_TRUE(!test_dir.empty());

-  WritableFile* writable_file;
-  ASSERT_OK(env_->NewWritableFile("/a/b", &writable_file));
+  unique_ptr<WritableFile> 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());
  ASSERT_OK(writable_file->Flush());
  ASSERT_OK(writable_file->Close());
-  delete writable_file;
+  writable_file.reset();
 }

 TEST(MemEnvTest, LargeWrite) {
@@ -158,15 +160,15 @@ TEST(MemEnvTest, LargeWrite) {
    write_data.append(1, static_cast<char>(i));
  }

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

-  SequentialFile* seq_file;
+  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"));

@@ -178,7 +180,6 @@ TEST(MemEnvTest, LargeWrite) {
    read += result.size();
  }
  ASSERT_TRUE(write_data == read_data);
-  delete seq_file;
  delete [] scratch;
 }

@@ -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_
@@ -183,6 +183,10 @@ extern void leveldb_options_destroy(leveldb_options_t*);
 extern void leveldb_options_set_comparator(
    leveldb_options_t*,
    leveldb_comparator_t*);
+extern void leveldb_options_set_compression_per_level(
+  leveldb_options_t* opt,
+  int* level_values,
+  size_t num_levels);
 extern void leveldb_options_set_filter_policy(
    leveldb_options_t*,
    leveldb_filterpolicy_t*);
@@ -199,6 +203,8 @@ extern void leveldb_options_set_max_open_files(leveldb_options_t*, int);
 extern void leveldb_options_set_cache(leveldb_options_t*, leveldb_cache_t*);
 extern void leveldb_options_set_block_size(leveldb_options_t*, size_t);
 extern void leveldb_options_set_block_restart_interval(leveldb_options_t*, int);
+extern void leveldb_options_set_compression_options(
+    leveldb_options_t* opt, int w_bits, int level, int strategy);

 enum {
  leveldb_no_compression = 0,
@@ -18,17 +18,20 @@
 #ifndef STORAGE_LEVELDB_INCLUDE_CACHE_H_
 #define STORAGE_LEVELDB_INCLUDE_CACHE_H_

+#include <memory>
 #include <stdint.h>
 #include "leveldb/slice.h"

 namespace leveldb {

+using std::shared_ptr;
+
 class Cache;

 // Create a new cache with a fixed size capacity.  This implementation
 // of Cache uses a least-recently-used eviction policy.
-extern Cache* NewLRUCache(size_t capacity);
-extern Cache* NewLRUCache(size_t capacity, int numShardBits);
+extern shared_ptr<Cache> NewLRUCache(size_t capacity);
+extern shared_ptr<Cache> NewLRUCache(size_t capacity, int numShardBits);

 class Cache {
 public:
@@ -53,7 +56,7 @@ class Cache {
  virtual Handle* Insert(const Slice& key, void* value, size_t charge,
                         void (*deleter)(const Slice& key, void* value)) = 0;

-  // If the cache has no mapping for "key", returns NULL.
+  // If the cache has no mapping for "key", returns nullptr.
  //
  // Else return a handle that corresponds to the mapping.  The caller
  // must call this->Release(handle) when the returned mapping is no
@@ -0,0 +1,46 @@
+// 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;
+};
+
+}  // namespace leveldb
+
+#endif  // STORAGE_LEVELDB_INCLUDE_COMPACTION_FILTER_H_
@@ -7,6 +7,7 @@

 #include <stdint.h>
 #include <stdio.h>
+#include <memory>
 #include <vector>
 #include "leveldb/iterator.h"
 #include "leveldb/options.h"
@@ -15,9 +16,11 @@

 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;
@@ -50,7 +53,7 @@ class DB {
  // Open the database with the specified "name".
  // Stores a pointer to a heap-allocated database in *dbptr and returns
  // OK on success.
-  // Stores NULL in *dbptr and returns a non-OK status on error.
+  // Stores nullptr in *dbptr and returns a non-OK status on error.
  // Caller should delete *dbptr when it is no longer needed.
  static Status Open(const Options& options,
                     const std::string& name,
@@ -80,6 +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.
@@ -93,7 +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
@@ -146,11 +189,18 @@ class DB {
  // needed to access the data.  This operation should typically only
  // be invoked by users who understand the underlying implementation.
  //
-  // begin==NULL is treated as a key before all keys in the database.
-  // end==NULL is treated as a key after all keys in the database.
+  // begin==nullptr is treated as a key before all keys in the database.
+  // end==nullptr is treated as a key after all keys in the database.
  // Therefore the following call will compact the entire database:
-  //    db->CompactRange(NULL, NULL);
-  virtual void CompactRange(const Slice* begin, const Slice* end) = 0;
+  //    db->CompactRange(nullptr, nullptr);
+  // 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;
@@ -182,7 +232,7 @@ class DB {
  virtual Status GetLiveFiles(std::vector<std::string>&,
                              uint64_t* manifest_file_size) = 0;

-  // The sequence number of the most recent transaction. 
+  // The sequence number of the most recent transaction.
  virtual SequenceNumber GetLatestSequenceNumber() = 0;

  // Return's an iterator for all writes since the sequence number
@@ -197,7 +247,7 @@ class DB {
  // cleared aggressively and the iterator might keep getting invalid before
  // an update is read.
  virtual Status GetUpdatesSince(SequenceNumber seq_number,
-                                 TransactionLogIterator** iter) = 0;
+                                 unique_ptr<TransactionLogIterator>* iter) = 0;
 private:
  // No copying allowed
  DB(const DB&);
@@ -15,6 +15,7 @@

 #include <cstdarg>
 #include <string>
+#include <memory>
 #include <vector>
 #include <stdint.h>
 #include "leveldb/status.h"
@@ -27,6 +28,40 @@ 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:
@@ -42,32 +77,37 @@ class Env {

  // Create a brand new sequentially-readable file with the specified name.
  // On success, stores a pointer to the new file in *result and returns OK.
-  // On failure stores NULL in *result and returns non-OK.  If the file does
+  // On failure stores nullptr in *result and returns non-OK.  If the file does
  // not exist, returns a non-OK status.
  //
  // The returned file will only be accessed by one thread at a time.
  virtual Status NewSequentialFile(const std::string& fname,
-                                   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
-  // *result and returns OK.  On failure stores NULL in *result and
+  // *result and returns OK.  On failure stores nullptr in *result and
  // returns non-OK.  If the file does not exist, returns a non-OK
  // status.
  //
  // The returned file may be concurrently accessed by multiple threads.
  virtual Status NewRandomAccessFile(const std::string& fname,
-                                     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
  // new file.  On success, stores a pointer to the new file in
-  // *result and returns OK.  On failure stores NULL in *result and
+  // *result and returns OK.  On failure stores nullptr in *result and
  // returns non-OK.
  //
  // The returned file will only be accessed by one thread at a time.
  virtual Status NewWritableFile(const std::string& fname,
-                                 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;
@@ -102,7 +142,7 @@ class Env {
                            const std::string& target) = 0;

  // Lock the specified file.  Used to prevent concurrent access to
-  // the same db by multiple processes.  On failure, stores NULL in
+  // the same db by multiple processes.  On failure, stores nullptr in
  // *lock and returns non-OK.
  //
  // On success, stores a pointer to the object that represents the
@@ -143,7 +183,8 @@ class Env {
  virtual Status GetTestDirectory(std::string* path) = 0;

  // Create and return a log file for storing informational messages.
-  virtual Status NewLogger(const std::string& fname, Logger** result) = 0;
+  virtual Status NewLogger(const std::string& fname,
+                           shared_ptr<Logger>* result) = 0;

  // Returns the number of micro-seconds since some fixed point in time. Only
  // useful for computing deltas of time.
@@ -218,6 +259,32 @@ class RandomAccessFile {
  // Safe for concurrent use by multiple threads.
  virtual Status Read(uint64_t offset, size_t n, Slice* result,
                      char* scratch) const = 0;
+
+  // Tries to get an unique ID for this file that will be the same each time
+  // 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 not have been modified.
+  //
+  // This function guarantees, for IDs from a given environment, two unique ids
+  // cannot be made equal to eachother by adding arbitrary bytes to one of
+  // them. That is, no unique ID is the prefix of another.
+  //
+  // This function guarantees that the returned ID will not be interpretable as
+  // a single varint.
+  //
+  // Note: these IDs are only valid for the duration of the process.
+  virtual size_t GetUniqueId(char* id, size_t max_size) const {
+    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
@@ -225,7 +292,8 @@ class RandomAccessFile {
 // at a time to the file.
 class WritableFile {
 public:
-  WritableFile() { }
+  WritableFile() : last_preallocated_block_(0), preallocation_block_size_ (0) {
+  }
  virtual ~WritableFile();

  virtual Status Append(const Slice& data) = 0;
@@ -250,7 +318,67 @@ class WritableFile {
    return 0;
  }

+  /*
+   * Get and set the default pre-allocation block size for writes to
+   * this file.  If non-zero, then Allocate will be used to extend the
+   * underlying storage of a file (generally via fallocate) if the Env
+   * instance supports it.
+   */
+  void SetPreallocationBlockSize(size_t size) {
+    preallocation_block_size_ = size;
+  }
+
+  virtual void GetPreallocationStatus(size_t* block_size,
+                                      size_t* last_allocated_block) {
+    *last_allocated_block = last_preallocated_block_;
+    *block_size = preallocation_block_size_;
+  }
+
+ protected:
+  // PrepareWrite performs any necessary preparation for a write
+  // before the write actually occurs.  This allows for pre-allocation
+  // of space on devices where it can result in less file
+  // fragmentation and/or less waste from over-zealous filesystem
+  // pre-allocation.
+  void PrepareWrite(size_t offset, size_t len) {
+    if (preallocation_block_size_ == 0) {
+      return;
+    }
+    // If this write would cross one or more preallocation blocks,
+    // determine what the last preallocation block necesessary to
+    // cover this write would be and Allocate to that point.
+    const auto block_size = preallocation_block_size_;
+    size_t new_last_preallocated_block =
+      (offset + len + block_size - 1) / block_size;
+    if (new_last_preallocated_block > last_preallocated_block_) {
+      size_t num_spanned_blocks =
+        new_last_preallocated_block - last_preallocated_block_;
+      Allocate(block_size * last_preallocated_block_,
+               block_size * num_spanned_blocks);
+      last_preallocated_block_ = new_last_preallocated_block;
+    }
+  }
+
+  /*
+   * Pre-allocate space for a file.
+   */
+  virtual Status Allocate(off_t offset, off_t len) {
+    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_;
  // No copying allowed
  WritableFile(const WritableFile&);
  void operator=(const WritableFile&);
@@ -287,7 +415,13 @@ class FileLock {
  void operator=(const FileLock&);
 };

-// Log the specified data to *info_log if info_log is non-NULL.
+// Log the specified data to *info_log if info_log is non-nullptr.
+extern void Log(const shared_ptr<Logger>& info_log, const char* format, ...)
+#   if defined(__GNUC__) || defined(__clang__)
+    __attribute__((__format__ (__printf__, 2, 3)))
+#   endif
+    ;
+
 extern void Log(Logger* info_log, const char* format, ...)
 #   if defined(__GNUC__) || defined(__clang__)
    __attribute__((__format__ (__printf__, 2, 3)))
@@ -315,14 +449,19 @@ class EnvWrapper : public Env {
  Env* target() const { return target_; }

  // The following text is boilerplate that forwards all methods to target()
-  Status NewSequentialFile(const std::string& f, SequentialFile** r) {
-    return target_->NewSequentialFile(f, r);
+  Status NewSequentialFile(const std::string& f,
+                           unique_ptr<SequentialFile>* r,
+                           const EnvOptions& options) {
+    return target_->NewSequentialFile(f, r, options);
  }
-  Status NewRandomAccessFile(const std::string& f, RandomAccessFile** r) {
-    return target_->NewRandomAccessFile(f, r);
+  Status NewRandomAccessFile(const std::string& f,
+                             unique_ptr<RandomAccessFile>* r,
+                             const EnvOptions& options) {
+    return target_->NewRandomAccessFile(f, r, options);
  }
-  Status NewWritableFile(const std::string& f, 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) {
@@ -359,7 +498,8 @@ class EnvWrapper : public Env {
  virtual Status GetTestDirectory(std::string* path) {
    return target_->GetTestDirectory(path);
  }
-  virtual Status NewLogger(const std::string& fname, Logger** result) {
+  virtual Status NewLogger(const std::string& fname,
+                           shared_ptr<Logger>* result) {
    return target_->NewLogger(fname, result);
  }
  uint64_t NowMicros() {
@@ -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 +1,146 @@
+// 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 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 Merge(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 above Merge() 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 Merge(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_
@@ -7,8 +7,12 @@

 #include <stddef.h>
 #include <string>
+#include <memory>
+#include <vector>
 #include <stdint.h>
 #include "leveldb/slice.h"
+#include "leveldb/statistics.h"
+#include "leveldb/memtablerep.h"

 namespace leveldb {

@@ -17,8 +21,11 @@ class Comparator;
 class Env;
 class FilterPolicy;
 class Logger;
+class MergeOperator;
 class Snapshot;
-class Statistics;
+class CompactionFilter;
+
+using std::shared_ptr;

 // DB contents are stored in a set of blocks, each of which holds a
 // sequence of key,value pairs.  Each block may be compressed before
@@ -59,6 +66,23 @@ 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
+  const MergeOperator* merge_operator;
+
+  // Allows an application to modify/delete a key-value during background
+  // compaction.
+  // Default: nullptr
+  const CompactionFilter* compaction_filter;
+
  // If true, the database will be created if it is missing.
  // Default: false
  bool create_if_missing;
@@ -81,10 +105,10 @@ struct Options {
  Env* env;

  // Any internal progress/error information generated by the db will
-  // be written to info_log if it is non-NULL, or to a file stored
-  // in the same directory as the DB contents if info_log is NULL.
-  // Default: NULL
-  Logger* info_log;
+  // be written to info_log if it is non-nullptr, or to a file stored
+  // in the same directory as the DB contents if info_log is nullptr.
+  // Default: nullptr
+  shared_ptr<Logger> info_log;

  // -------------------
  // Parameters that affect performance
@@ -108,6 +132,15 @@ 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).
@@ -118,10 +151,10 @@ struct Options {
  // Control over blocks (user data is stored in a set of blocks, and
  // a block is the unit of reading from disk).

-  // If non-NULL, use the specified cache for blocks.
+  // If non-NULL use the specified cache for blocks.
  // If NULL, leveldb will automatically create and use an 8MB internal cache.
-  // Default: NULL
-  Cache* block_cache;
+  // Default: nullptr
+  shared_ptr<Cache> block_cache;

  // Approximate size of user data packed per block.  Note that the
  // block size specified here corresponds to uncompressed data.  The
@@ -159,24 +192,24 @@ struct Options {
  // are cases where most lower levels would like to quick compression
  // algorithm while the higher levels (which have more data) use
  // compression algorithms that have better compression but could
-  // be slower. This array, if non NULL, should have an entry for
-  // each level of the database. This array, if non NULL, overides the
+  // be slower. This array, if non nullptr, should have an entry for
+  // each level of the database. This array, if non nullptr, overides the
  // value specified in the previous field 'compression'. The caller is
  // reponsible for allocating memory and initializing the values in it
  // before invoking Open(). The caller is responsible for freeing this
  // array and it could be freed anytime after the return from Open().
  // This could have been a std::vector but that makes the equivalent
  // java/C api hard to construct.
-  CompressionType* compression_per_level;
+  std::vector<CompressionType> compression_per_level;

  //different options for compression algorithms
  CompressionOptions compression_opts;

-  // If non-NULL, use the specified filter policy to reduce disk reads.
+  // If non-nullptr, use the specified filter policy to reduce disk reads.
  // Many applications will benefit from passing the result of
  // NewBloomFilterPolicy() here.
  //
-  // Default: NULL
+  // Default: nullptr
  const FilterPolicy* filter_policy;

  // Number of levels for this database
@@ -186,9 +219,9 @@ 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.
@@ -232,6 +265,12 @@ 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
@@ -252,7 +291,9 @@ struct Options {
  int max_grandparent_overlap_factor;

  // If non-null, then we should collect metrics about database operations
-  Statistics* statistics;
+  // Statistics objects should not be shared between DB instances as
+  // it does not use any locks to prevent concurrent updates.
+  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
@@ -304,41 +345,66 @@ struct Options {
  // log file.
  size_t max_log_file_size;

-  // Puts are delayed when any level has a compaction score that
-  // exceeds rate_limit. This is ignored when <= 1.0.
-  double rate_limit;
+  // Time for the info log file to roll (in seconds).
+  // If specified with non-zero value, log file will be rolled
+  // if it has been active longer than `log_file_time_to_roll`.
+  // Default: 0 (disabled)
+  size_t log_file_time_to_roll;
+
+  // Maximal info log files to be kept.
+  // Default: 1000
+  size_t keep_log_file_num;
+
+  // 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;
+
+  // 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,
  // then no block cache should be used, and the block_cache should
-  // point to a NULL object.
+  // point to a nullptr object.
  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();

-  void Dump(Logger * log) const;
+  void Dump(Logger* log) const;

-  // 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);
+  // Set appropriate parameters for bulk loading.
+  // The reason that this is a function that returns "this" instead of a
+  // constructor is to enable chaining of multiple similar calls in the future.
+  //
+  // All data will be in level 0 without any automatic compaction.
+  // It's recommended to manually call CompactRange(NULL, NULL) before reading
+  // from the database, because otherwise the read can be very slow.
+  Options* PrepareForBulkLoad();

  // Disable automatic compactions. Manual compactions can still
  // be issued on this database.
@@ -353,6 +419,82 @@ struct Options {
  // deleted.
  // Default : 0
  uint64_t WAL_ttl_seconds;
+
+  // Number of bytes to preallocate (via fallocate) the manifest
+  // files.  Default is 4mb, which is reasonable to reduce random IO
+  // as well as prevent overallocation for mounts that preallocate
+  // large amounts of data (such as xfs's allocsize option).
+  size_t manifest_preallocation_size;
+
+  // 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;
+
+  // 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;
+
 };

 // Options that control read operations
@@ -367,21 +509,21 @@ struct ReadOptions {
  // Default: true
  bool fill_cache;

-  // If "snapshot" is non-NULL, read as of the supplied snapshot
+  // If "snapshot" is non-nullptr, read as of the supplied snapshot
  // (which must belong to the DB that is being read and which must
-  // not have been released).  If "snapshot" is NULL, use an impliicit
+  // not have been released).  If "snapshot" is nullptr, use an impliicit
  // snapshot of the state at the beginning of this read operation.
-  // Default: NULL
+  // Default: nullptr
  const Snapshot* snapshot;

  ReadOptions()
      : verify_checksums(false),
        fill_cache(true),
-        snapshot(NULL) {
+        snapshot(nullptr) {
  }
  ReadOptions(bool cksum, bool cache) :
              verify_checksums(cksum), fill_cache(cache),
-              snapshot(NULL) {
+              snapshot(nullptr) {
  }
 };

@@ -5,12 +5,21 @@
 #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 {

 /**
 * 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 {
@@ -24,9 +33,138 @@ enum Tickers {
  COMPACTION_KEY_DROP_NEWER_ENTRY = 3, // key was written with a newer value.
  COMPACTION_KEY_DROP_OBSOLETE = 4, // The key is obsolete.
  COMPACTION_KEY_DROP_USER = 5, // user compaction function has dropped the key.
-  TICKER_ENUM_MAX = 6,
+  // Number of keys written to the database via the Put and Write call's
+  NUMBER_KEYS_WRITTEN = 6,
+  // Number of Keys read,
+  NUMBER_KEYS_READ = 7,
+  // Bytes written / read
+  BYTES_WRITTEN = 8,
+  BYTES_READ = 9,
+  NO_FILE_CLOSES = 10,
+  NO_FILE_OPENS = 11,
+  NO_FILE_ERRORS = 12,
+  // 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,
+
+  TICKER_ENUM_MAX = 22
 };

+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" }
+};
+
+/**
+ * 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,
+  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,
+  HISTOGRAM_ENUM_MAX = 17
+};
+
+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"}
+};
+
+struct HistogramData {
+  double median;
+  double percentile95;
+  double percentile99;
+  double average;
+  double standard_deviation;
+};
+
+
+class Histogram {
+ public:
+  // clear's the histogram
+  virtual void Clear() = 0;
+  virtual ~Histogram();
+  // Add a value to be recorded in the histogram.
+  virtual void Add(uint64_t value) = 0;
+
+  virtual std::string ToString() const = 0;
+
+  // Get statistics
+  virtual double Median() const = 0;
+  virtual double Percentile(double p) const = 0;
+  virtual double Average() const = 0;
+  virtual double StandardDeviation() const = 0;
+  virtual void Data(HistogramData * const data) const = 0;
+
+};

 /**
 * A dumb ticker which keeps incrementing through its life time.
@@ -36,50 +174,48 @@ class Ticker {
 public:
  Ticker() : count_(0) { }

-  inline void recordTick() {
+ inline void recordTick() {
    count_++;
  }

+  inline void recordTick(int count) {
+    count_ += count;
+  }
+
  inline uint64_t getCount() {
    return count_;
  }

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

 // Analyze the performance of a db
 class Statistics {
 public:
-  // Create an Statistics object with default values for all fields.
-  Statistics() : numFileOpens_(0), numFileCloses_(0),
-                 numFileErrors_(0) {}
-
-  virtual void incNumFileOpens() = 0;
-  virtual void incNumFileCloses() = 0;
-  virtual void incNumFileErrors() = 0;
-
-  virtual long getNumFileOpens() { return numFileOpens_;}
-  virtual long getNumFileCloses() { return numFileCloses_;}
-  virtual long getNumFileErrors() { return numFileErrors_;}
-  virtual ~Statistics() {}

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

- protected:
-  long numFileOpens_;
-  long numFileCloses_;
-  long numFileErrors_;
+  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, Tickers ticker) {
-  if (statistics != NULL) {
-    statistics->recordTick(ticker);
+inline void RecordTick(std::shared_ptr<Statistics> statistics,
+                       Tickers ticker,
+                       uint64_t count = 1) {
+  assert(HistogramsNameMap.size() == HISTOGRAM_ENUM_MAX);
+  assert(TickersNameMap.size() == TICKER_ENUM_MAX);
+  if (statistics) {
+    statistics->recordTick(ticker, count);
  }
-};
+}
 }  // namespace leveldb

 #endif  // STORAGE_LEVELDB_INCLUDE_STATISTICS_H_
@@ -21,7 +21,7 @@ namespace leveldb {
 class Status {
 public:
  // Create a success status.
-  Status() : state_(NULL) { }
+  Status() : state_(nullptr) { }
  ~Status() { delete[] state_; }

  // Copy the specified status.
@@ -47,9 +47,12 @@ 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_ == NULL); }
+  bool ok() const { return (state_ == nullptr); }

  // Returns true iff the status indicates a NotFound error.
  bool IsNotFound() const { return code() == kNotFound; }
@@ -57,15 +60,24 @@ class Status {
  // Returns true iff the status indicates a Corruption error.
  bool IsCorruption() const { return code() == kCorruption; }

+  // Returns true iff the status indicates a NotSupported error.
+  bool IsNotSupported() const { return code() == kNotSupported; }
+
+  // Returns true iff the status indicates an InvalidArgument error.
+  bool IsInvalidArgument() const { return code() == kInvalidArgument; }
+
  // 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;

 private:
-  // OK status has a NULL state_.  Otherwise, state_ is a new[] array
+  // OK status has a nullptr state_.  Otherwise, state_ is a new[] array
  // of the following form:
  //    state_[0..3] == length of message
  //    state_[4]    == code
@@ -78,11 +90,12 @@ class Status {
    kCorruption = 2,
    kNotSupported = 3,
    kInvalidArgument = 4,
-    kIOError = 5
+    kIOError = 5,
+    kMergeInProgress = 6
  };

  Code code() const {
-    return (state_ == NULL) ? kOk : static_cast<Code>(state_[4]);
+    return (state_ == nullptr) ? kOk : static_cast<Code>(state_[4]);
  }

  Status(Code code, const Slice& msg, const Slice& msg2);
@@ -90,14 +103,14 @@ class Status {
 };

 inline Status::Status(const Status& s) {
-  state_ = (s.state_ == NULL) ? NULL : CopyState(s.state_);
+  state_ = (s.state_ == nullptr) ? nullptr : CopyState(s.state_);
 }
 inline void Status::operator=(const Status& s) {
  // The following condition catches both aliasing (when this == &s),
  // and the common case where both s and *this are ok.
  if (state_ != s.state_) {
    delete[] state_;
-    state_ = (s.state_ == NULL) ? NULL : CopyState(s.state_);
+    state_ = (s.state_ == nullptr) ? nullptr : CopyState(s.state_);
  }
 }

@@ -8,6 +8,11 @@
 namespace leveldb {


+struct BatchResult {
+  SequenceNumber sequence;
+  std::unique_ptr<WriteBatch> writeBatchPtr;
+};
+
 //  A TransactionLogIterator is used to iterate over the Transaction's in a db.
 class TransactionLogIterator {
 public:
@@ -16,19 +21,21 @@ class TransactionLogIterator {

  // An iterator is either positioned at a WriteBatch or not valid.
  // This method returns true if the iterator is valid.
+  // Can read data from a valid iterator.
  virtual bool Valid() = 0;

  // Moves the iterator to the next WriteBatch.
  // REQUIRES: Valid() to be true.
  virtual void Next() = 0;

-  // Return's ok if the iterator is in a valid stated.
-  // Return the Error Status when the iterator is not Valid.
+  // Return's ok if the iterator is valid.
+  // Return the Error when something has gone wrong.
  virtual Status status() = 0;

  // If valid return's the current write_batch and the sequence number of the
  // latest transaction contained in the batch.
-  virtual void GetBatch(WriteBatch* batch, SequenceNumber* seq) = 0;
+  // ONLY use if Valid() is true and status() is OK.
+  virtual BatchResult GetBatch() = 0;
 };
 } //  namespace leveldb

@@ -36,6 +36,10 @@ 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);

@@ -47,13 +51,20 @@ class WriteBatch {
   public:
    virtual ~Handler();
    virtual void Put(const Slice& key, const Slice& value) = 0;
+    // Merge is not pure virtual. Otherwise, we would break existing
+    // clients of Handler on a source code level.
+    // The default implementation simply throws a runtime exception.
+    virtual void Merge(const Slice& key, const Slice& value);
    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) {}

@@ -0,0 +1,154 @@
+// 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 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 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_
@@ -36,12 +36,12 @@
  <parent>
    <groupId>org.fusesource.leveldbjni.fb</groupId>
    <artifactId>leveldbjni-project</artifactId>
-    <version>1.5.6</version>
+    <version>1.5.7</version>
  </parent>

  <groupId>org.fusesource.leveldbjni.fb</groupId>
  <artifactId>leveldbjni-all</artifactId>
-  <version>1.5.6</version>
+  <version>1.5.7</version>
  
  <name>${project.artifactId}</name>
  <description>An uber jar which contains all the leveldbjni platform libraries and dependencies</description>
@@ -50,27 +50,27 @@
    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni-osx</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
    </dependency>
    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni-linux32</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
    </dependency>
    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni-linux64</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
    </dependency>
    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni-win32</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
    </dependency>
    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni-win64</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
    </dependency>
    
  </dependencies>
@@ -36,12 +36,12 @@
  <parent>
    <groupId>org.fusesource.leveldbjni.fb</groupId>
    <artifactId>leveldbjni-project</artifactId>
-    <version>1.5.6</version>
+    <version>1.5.7</version>
  </parent>

  <groupId>org.fusesource.leveldbjni.fb</groupId>
  <artifactId>leveldbjni-linux32</artifactId>
-  <version>1.5.6</version>
+  <version>1.5.7</version>
  
  <name>${project.artifactId}</name>
  <description>The leveldbjni linux 32 native libraries</description>
@@ -50,7 +50,7 @@
    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
    </dependency>
  </dependencies>

@@ -36,12 +36,12 @@
  <parent>
    <groupId>org.fusesource.leveldbjni.fb</groupId>
    <artifactId>leveldbjni-project</artifactId>
-    <version>1.5.6</version>
+    <version>1.5.7</version>
  </parent>

  <groupId>org.fusesource.leveldbjni.fb</groupId>
  <artifactId>leveldbjni-linux64</artifactId>
-  <version>1.5.6</version>
+  <version>1.5.7</version>
  
  <name>${project.artifactId}</name>
  <description>The leveldbjni linux 64 native libraries</description>
@@ -50,7 +50,7 @@
    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
    </dependency>
  </dependencies>

@@ -36,12 +36,12 @@
  <parent>
    <groupId>org.fusesource.leveldbjni.fb</groupId>
    <artifactId>leveldbjni-project</artifactId>
-    <version>1.5.6</version>
+    <version>1.5.7</version>
  </parent>

  <groupId>org.fusesource.leveldbjni.fb</groupId>
  <artifactId>leveldbjni-osx</artifactId>
-  <version>1.5.6</version>
+  <version>1.5.7</version>
  
  <name>${project.artifactId}</name>
  <description>The leveldbjni OS X universal native libraries</description>
@@ -50,13 +50,13 @@
    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
    </dependency>

    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
      <type>test-jar</type>
      <scope>test</scope>
    </dependency>
@@ -36,12 +36,12 @@
  <parent>
    <groupId>org.fusesource.leveldbjni.fb</groupId>
    <artifactId>leveldbjni-project</artifactId>
-    <version>1.5.6</version>
+    <version>1.5.7</version>
  </parent>

  <groupId>org.fusesource.leveldbjni.fb</groupId>
  <artifactId>leveldbjni-win32</artifactId>
-  <version>1.5.6</version>
+  <version>1.5.7</version>
  
  <name>${project.artifactId}</name>
  <description>The leveldbjni Windows 32 bit native libraries</description>
@@ -50,7 +50,7 @@
    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
    </dependency>
  </dependencies>

@@ -36,12 +36,12 @@
  <parent>
    <groupId>org.fusesource.leveldbjni.fb</groupId>
    <artifactId>leveldbjni-project</artifactId>
-    <version>1.5.6</version>
+    <version>1.5.7</version>
  </parent>

  <groupId>org.fusesource.leveldbjni.fb</groupId>
  <artifactId>leveldbjni-win64</artifactId>
-  <version>1.5.6</version>
+  <version>1.5.7</version>
  
  <name>${project.artifactId}</name>
  <description>The leveldbjni Windows 64 bit native libraries</description>
@@ -50,7 +50,7 @@
    <dependency>
      <groupId>org.fusesource.leveldbjni.fb</groupId>
      <artifactId>leveldbjni</artifactId>
-      <version>1.5.6</version>
+      <version>1.5.7</version>
    </dependency>
  </dependencies>

@@ -36,12 +36,12 @@
  <parent>
    <groupId>org.fusesource.leveldbjni.fb</groupId>
    <artifactId>leveldbjni-project</artifactId>
-    <version>1.5.6</version>
+    <version>1.5.7</version>
  </parent>

  <groupId>org.fusesource.leveldbjni.fb</groupId>
  <artifactId>leveldbjni</artifactId>
-  <version>1.5.6</version>
+  <version>1.5.7</version>
  <packaging>jar</packaging>
  
  <name>${project.artifactId}</name>
@@ -41,7 +41,7 @@

  <groupId>org.fusesource.leveldbjni.fb</groupId>
  <artifactId>leveldbjni-project</artifactId>
-  <version>1.5.6</version>
+  <version>1.5.7</version>
  <packaging>pom</packaging>
  
  <name>${project.artifactId}</name>
@@ -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
@@ -0,0 +1,99 @@
+#!/bin/bash
+
+set -e
+
+NUM=10000000
+
+if [ $# -eq 1 ];then
+  DATA_DIR=$1
+elif [ $# -eq 2 ];then
+  DATA_DIR=$1
+  STAT_FILE=$2
+fi
+
+# On the production build servers, set data and stat
+# files/directories not in /tmp or else the tempdir cleaning
+# scripts will make you very unhappy.
+DATA_DIR=${DATA_DIR:-$(mktemp --tmpdir -d leveldb_XXXX)}
+STAT_FILE=${STAT_FILE:-$(mktemp --tmpdir -u leveldb_test_stats_XXXX)}
+
+function cleanup {
+  rm -rf $DATA_DIR
+  rm -f $STAT_FILE.fillseq
+  rm -f $STAT_FILE.readrandom
+  rm -f $STAT_FILE.overwrite
+}
+
+trap cleanup EXIT
+
+function send_to_ods {
+  key="$1"
+  value="$2"
+
+  if [ -z "$value" ];then
+    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=$value"
+}
+
+make clean
+make db_bench -j$(nproc)
+
+./db_bench \
+    --benchmarks=fillseq \
+    --db=$DATA_DIR \
+    --use_existing_db=0 \
+    --bloom_bits=10 \
+    --num=$NUM \
+    --writes=$NUM \
+    --cache_size=6442450944 \
+    --cache_numshardbits=6 \
+    --open_files=55000 \
+    --statistics=1 \
+    --histogram=1 \
+    --disable_data_sync=1 \
+    --disable_wal=1 \
+    --sync=0  > ${STAT_FILE}.fillseq
+
+./db_bench \
+    --benchmarks=overwrite \
+    --db=$DATA_DIR \
+    --use_existing_db=1 \
+    --bloom_bits=10 \
+    --num=$NUM \
+    --writes=$((NUM / 2)) \
+    --cache_size=6442450944 \
+    --cache_numshardbits=6  \
+    --open_files=55000 \
+    --statistics=1 \
+    --histogram=1 \
+    --disable_data_sync=1 \
+    --disable_wal=1 \
+    --sync=0 \
+    --threads=8 > ${STAT_FILE}.overwrite
+
+./db_bench \
+    --benchmarks=readrandom \
+    --db=$DATA_DIR \
+    --use_existing_db=1 \
+    --bloom_bits=10 \
+    --num=$NUM \
+    --reads=$((NUM / 100)) \
+    --cache_size=6442450944 \
+    --cache_numshardbits=6 \
+    --open_files=55000 \
+    --statistics=1 \
+    --histogram=1 \
+    --disable_data_sync=1 \
+    --disable_wal=1 \
+    --sync=0 \
+    --threads=128 > ${STAT_FILE}.readrandom
+
+OVERWRITE_OPS=$(awk '/overwrite/ {print $5}' $STAT_FILE.overwrite)
+FILLSEQ_OPS=$(awk '/fillseq/ {print $5}' $STAT_FILE.fillseq)
+READRANDOM_OPS=$(awk '/readrandom/ {print $5}' $STAT_FILE.readrandom)
+
+send_to_ods rocksdb.build.overwrite.qps $OVERWRITE_OPS
+send_to_ods rocksdb.build.fillseq.qps $FILLSEQ_OPS
+send_to_ods rocksdb.build.readrandom.qps $READRANDOM_OPS
@@ -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 {
@@ -47,13 +48,13 @@ Block::~Block() {
 // and the length of the value in "*shared", "*non_shared", and
 // "*value_length", respectively.  Will not derefence past "limit".
 //
-// If any errors are detected, returns NULL.  Otherwise, returns a
+// If any errors are detected, returns nullptr.  Otherwise, returns a
 // pointer to the key delta (just past the three decoded values).
 static inline const char* DecodeEntry(const char* p, const char* limit,
                                      uint32_t* shared,
                                      uint32_t* non_shared,
                                      uint32_t* value_length) {
-  if (limit - p < 3) return NULL;
+  if (limit - p < 3) return nullptr;
  *shared = reinterpret_cast<const unsigned char*>(p)[0];
  *non_shared = reinterpret_cast<const unsigned char*>(p)[1];
  *value_length = reinterpret_cast<const unsigned char*>(p)[2];
@@ -61,13 +62,13 @@ static inline const char* DecodeEntry(const char* p, const char* limit,
    // Fast path: all three values are encoded in one byte each
    p += 3;
  } else {
-    if ((p = GetVarint32Ptr(p, limit, shared)) == NULL) return NULL;
-    if ((p = GetVarint32Ptr(p, limit, non_shared)) == NULL) return NULL;
-    if ((p = GetVarint32Ptr(p, limit, value_length)) == NULL) return NULL;
+    if ((p = GetVarint32Ptr(p, limit, shared)) == nullptr) return nullptr;
+    if ((p = GetVarint32Ptr(p, limit, non_shared)) == nullptr) return nullptr;
+    if ((p = GetVarint32Ptr(p, limit, value_length)) == nullptr) return nullptr;
  }

  if (static_cast<uint32_t>(limit - p) < (*non_shared + *value_length)) {
-    return NULL;
+    return nullptr;
  }
  return p;
 }
@@ -173,7 +174,7 @@ class Block::Iter : public Iterator {
      const char* key_ptr = DecodeEntry(data_ + region_offset,
                                        data_ + restarts_,
                                        &shared, &non_shared, &value_length);
-      if (key_ptr == NULL || (shared != 0)) {
+      if (key_ptr == nullptr || (shared != 0)) {
        CorruptionError();
        return;
      }
@@ -236,7 +237,7 @@ class Block::Iter : public Iterator {
    // Decode next entry
    uint32_t shared, non_shared, value_length;
    p = DecodeEntry(p, limit, &shared, &non_shared, &value_length);
-    if (p == NULL || key_.size() < shared) {
+    if (p == nullptr || key_.size() < shared) {
      CorruptionError();
      return false;
    } 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();