Summary:
The method Finalize() recomputes the compaction score of each
level and then sorts these score from largest to smallest. The
idea is that the level with the largest compaction score will
be a better candidate for compaction.  There are usually very
few levels, and a bubble sort code was used to sort these
compaction scores. There existed a bug in the sorting code that
skipped looking at the score for the n-1 level. This meant that
even if the compaction score of the n-1 level is large, it will
not be picked for compaction.

This patch fixes the bug and also introduces "asserts" in the
code to detect any possible inconsistencies caused by future bugs.

This bug existed in the very first code change that introduced
multi-threaded compaction to the leveldb code. That version of
code was committed on Oct 19th via
https://github.com/facebook/leveldb/commit/1ca0584345af85d2dccc434f451218119626d36e

Test Plan: make clean check OPT=-g

Reviewers: emayanke, sheki, MarkCallaghan

Reviewed By: sheki

CC: leveldb

Differential Revision: https://reviews.facebook.net/D6837

Summary:
make check OPT=-g fails with the following assert.
==== Test DBTest.ApproximateSizes
db_test: db/version_set.cc:765: void leveldb::VersionSet::Builder::CheckConsistencyForDeletes(leveldb::VersionEdit*, int, int): Assertion `found' failed.

The assertion was that file #7 that was being deleted did not
preexists, but actualy it did pre-exist as shown in the manifest
dump shows below. The bug was that we did not check for file
existance at the same level.

*************************Edit[0] = VersionEdit {
  Comparator: leveldb.BytewiseComparator
}

*************************Edit[1] = VersionEdit {
  LogNumber: 8
  PrevLogNumber: 0
  NextFile: 9
  LastSeq: 80
  AddFile: 0 7 8005319 'key000000' @ 1 : 1 .. 'key000079' @ 80 : 1
}

*************************Edit[2] = VersionEdit {
  LogNumber: 8
  PrevLogNumber: 0
  NextFile: 13
  LastSeq: 80
  CompactPointer: 0 'key000079' @ 80 : 1
  DeleteFile: 0 7
  AddFile: 1 9 2101425 'key000000' @ 1 : 1 .. 'key000020' @ 21 : 1
  AddFile: 1 10 2101425 'key000021' @ 22 : 1 .. 'key000041' @ 42 : 1
  AddFile: 1 11 2101425 'key000042' @ 43 : 1 .. 'key000062' @ 63 : 1
  AddFile: 1 12 1701165 'key000063' @ 64 : 1 .. 'key000079' @ 80 : 1
}

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:

Summary:
Fix compilation error while compiling with OPT=-g

Test Plan:
make clean check OPT=-g

Reviewers:

CC:

Task ID: #

Blame Rev:

7889e094

Summary:
Fix compilation error introduced by previous commit
7889e094

Test Plan:
make clean check

Summary:
The manifest file contains a series of edits. If the verbose
option is switched on, then print each individual edit in the
manifest file. This helps in debugging.

Test Plan: make clean manifest_dump

Reviewers: emayanke, sheki

Reviewed By: sheki

CC: leveldb

Differential Revision: https://reviews.facebook.net/D6807

Summary:
StringStream.clear() does not clear the stream. It sets some flags.
Who knew? Fixing that is not printing the stuff again and again.

Test Plan: ran it on a local db

Reviewers: dhruba, emayanke

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D6795

Summary: The new function MinLevelToCompress in db_test.cc was incomplete. It needs to tell the calling function-TEST whether the test has to be skipped or not

Test Plan: make all;./db_test

Reviewers: dhruba, heyongqiang

Reviewed By: dhruba

CC: sheki

Differential Revision: https://reviews.facebook.net/D6771

Summary:
Add option to read WAL and print a summary for each record.
facebook task => #1885013

E.G. Output :
./ldb dump_wal --walfile=/tmp/leveldbtest-5907/dbbench/026122.log --header
Sequence,Count,ByteSize
49981,1,100033
49981,1,100033
49982,1,100033
49981,1,100033
49982,1,100033
49983,1,100033
49981,1,100033
49982,1,100033
49983,1,100033
49984,1,100033
49981,1,100033
49982,1,100033

Test Plan:
Works run
./ldb read_wal --wal-file=/tmp/leveldbtest-5907/dbbench/000078.log --header

Reviewers: dhruba, heyongqiang

Reviewed By: dhruba

CC: emayanke, leveldb, zshao

Differential Revision: https://reviews.facebook.net/D6675

Summary:
The manifest file contains a series of edits. If the verbose
option is switched on, then print each individual edit in the
manifest file. This helps in debugging.

Test Plan: make clean manifest_dump

Reviewers: emayanke, sheki

Reviewed By: sheki

CC: leveldb

Differential Revision: https://reviews.facebook.net/D6807

Summary:
StringStream.clear() does not clear the stream. It sets some flags.
Who knew? Fixing that is not printing the stuff again and again.

Test Plan: ran it on a local db

Reviewers: dhruba, emayanke

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D6795

Summary:
dbstress has an option to reopen the database. Make it such that the
previous handle is not closed before we reopen, this simulates a
situation similar to a process crash.

Added new api to DMImpl to remove the lock file.

Test Plan: run db_stress

Reviewers: emayanke

Reviewed By: emayanke

CC: leveldb

Differential Revision: https://reviews.facebook.net/D6777

Summary: The new function MinLevelToCompress in db_test.cc was incomplete. It needs to tell the calling function-TEST whether the test has to be skipped or not

Test Plan: make all;./db_test

Reviewers: dhruba, heyongqiang

Reviewed By: dhruba

CC: sheki

Differential Revision: https://reviews.facebook.net/D6771

Summary:
Add option to read WAL and print a summary for each record.
facebook task => #1885013

E.G. Output :
./ldb dump_wal --walfile=/tmp/leveldbtest-5907/dbbench/026122.log --header
Sequence,Count,ByteSize
49981,1,100033
49981,1,100033
49982,1,100033
49981,1,100033
49982,1,100033
49983,1,100033
49981,1,100033
49982,1,100033
49983,1,100033
49984,1,100033
49981,1,100033
49982,1,100033

Test Plan:
Works run
./ldb read_wal --wal-file=/tmp/leveldbtest-5907/dbbench/000078.log --header

Reviewers: dhruba, heyongqiang

Reviewed By: dhruba

CC: emayanke, leveldb, zshao

Differential Revision: https://reviews.facebook.net/D6675

Summary:
Create more than one background compaction thread if specified.
This code peice is similar to what exists in db_bench.

Test Plan: make check

Differential Revision: https://reviews.facebook.net/D6753

Conflicts:
	db/db_impl.h

Summary:
The value specified in max_grandparent_overlap_factor is used to
limit the file size in a compaction run. This patch makes it
configurable when using db_bench.

Test Plan: make clean db_bench

Reviewers: MarkCallaghan, heyongqiang

Reviewed By: heyongqiang

CC: leveldb

Differential Revision: https://reviews.facebook.net/D6729

Summary:

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:

Summary:
The fbcode compilation was always switching on msse by default.
This patch keeps the same behaviour but allows the compilation
process to switch off msse if needed.

If one does not want to use sse, then do the following:
export USE_SSE=0
make clean all

Test Plan: make clean all

Reviewers: heyongqiang

Reviewed By: heyongqiang

CC: leveldb

Differential Revision: https://reviews.facebook.net/D6717

Summary:
There are applications that operate on multiple leveldb instances.
These applications will like to pass in an opaque type for each
leveldb instance and this type should be passed back to the application
with every invocation of the CompactionFilter api.

Test Plan: Enehanced unit test for opaque parameter to CompactionFilter.

Reviewers: heyongqiang

Reviewed By: heyongqiang

CC: MarkCallaghan, sheki, emayanke

Differential Revision: https://reviews.facebook.net/D6711

Summary:
Compilation used to fail with the error:
db/version_set.cc:1773: error: ‘number_of_files_to_sort_’ is not a member of ‘leveldb::VersionSet’

I created a new method called CheckConsistencyForDeletes() so that
all the high cost checking is done only when OPT=-g is specified.

I also fixed a bug in PickCompactionBySize that was triggered when
OPT=-g was switched on. The base_index in the compaction record
was not set correctly.

Test Plan: make check OPT=-g

Differential Revision: https://reviews.facebook.net/D6687

Summary:
The db_bench utility was broken in 1.5.4.fb because of a
signed-unsigned comparision.

The static variable FLAGS_min_level_to_compress was recently
changed from int to 'unsigned in' but it is initilized to a
nagative value -1.

The segfault is of this type:
Program received signal SIGSEGV, Segmentation fault.
Open (this=0x7fffffffdee0) at db/db_bench.cc:939
939	db/db_bench.cc: No such file or directory.
(gdb) where

Test Plan: run db_bench with no options.

Reviewers: heyongqiang

Reviewed By: heyongqiang

CC: MarkCallaghan, emayanke, sheki

Differential Revision: https://reviews.facebook.net/D6663

Introducing "database reopens" into the stress test. Database will reopen after a specified number of iterations (configurable) of each thread when they will wait for the databse to reopen.

Summary: FLAGS_reopen (configurable) specifies the number of times the databse is to be reopened. FLAGS_ops_per_thread is divided into points based on that reopen field. At these points all threads come together to wait for the databse to reopen. Each thread "votes" for the database to reopen and when all have voted, the database reopens.

Test Plan: make all;./db_stress

Reviewers: dhruba, MarkCallaghan, sheki, asad, heyongqiang

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D6627

Summary:
I changed the reduce_num_levels logic to avoid "compactRange()" call if the current number of levels in use (levels that contain files) is smaller than the new num of levels.
And that change breaks the assert in reduce_levels_test

Test Plan: run reduce_levels_test

Reviewers: dhruba, MarkCallaghan

Reviewed By: dhruba

CC: emayanke, sheki

Differential Revision: https://reviews.facebook.net/D6651

Summary:
make clean check OPT=-g fails
leveldb::DBStatistics::getTickerCount(leveldb::Tickers)’:
./db/db_statistics.h:34: error: ‘MAX_NO_TICKERS’ was not declared in this scope
util/ldb_cmd.cc:255: warning: left shift count >= width of type

Test Plan:
make clean check OPT=-g

Reviewers:

CC:

Task ID: #

Blame Rev:

Summary: Record BloomFliter hits and drop off reasons during compaction.

Test Plan: Unit tests work.

Reviewers: dhruba, heyongqiang

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D6591

Summary:
disable size compaction in ldb reduce_levels, this will avoid compactions rather than the manual comapction,

added --compression=none|snappy|zlib|bzip2 and --file_size= per-file size to ldb reduce_levels command

Test Plan: run ldb

Reviewers: dhruba, MarkCallaghan

Reviewed By: dhruba

CC: sheki, emayanke

Differential Revision: https://reviews.facebook.net/D6597

Summary:
Preparing for new release 1.5.4.fb

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:

Summary: Stress test modified to do deletes and later verify them

Test Plan: running the test: db_stress

Reviewers: dhruba, heyongqiang, asad, sheki, MarkCallaghan

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D6567

Summary:
Prototype stat's collection. Diff is a good estimate of what
the final code will look like.
A few assumptions :
  * Used a global static instance of the statistics object. Plan to pass
  it to each internal function. Static allows metrics only at app
  level.
  * In the Ticker's do not do any locking. Depend on the mutex at each
   function of LevelDB. If we ever remove the mutex, we should change
   here too. The other option is use atomic objects anyways as there
   won't be any contention as they will be always acquired only by one
   thread.
  * The counters are dumb, increment through lifecycle. Plan to use ods
    etc to get last5min stat etc.

Test Plan:
made changes in db_bench
Ran ./db_bench --statistics=1 --num=10000 --cache_size=5000
This will print the cache hit/miss stats.

Reviewers: dhruba, heyongqiang

Differential Revision: https://reviews.facebook.net/D6441

Summary:
When a new version is created, we sort all the files at every
level based on their size. This is necessary because we want
to compact the largest file first. The sorting takes quite a
bit of CPU.

Moved the sorting code to be outside the mutex. Also, the
earlier code was sorting files at all levels but we do not
need to sort the highest-number level because those files
are never the cause of any compaction. To reduce sorting
costs, we sort only the first few files in each level
because it is likely that those are the only files in that
level that will be picked for compaction.

At steady state, I have seen that this patch increase
throughout from 1500 writes/sec to 1700 writes/sec at the
end of a 72 hour run. The cpu saving by not sorting the
last level was not distinctive in this test run because
there were only 100K files in the highest numbered level.
I expect the cpu saving to be significant when the number of
files is much higher.

This is mostly an early preview and not ready for rigorous review.

With this patch, the writs/sec is now bottlenecked not by the sorting code but by GetOverlappingInputs. I am working on a patch to optimize GetOverlappingInputs.

Test Plan: make check

Reviewers: MarkCallaghan, heyongqiang

Reviewed By: heyongqiang

Differential Revision: https://reviews.facebook.net/D6411

Summary:
Fixed compilation error in previous merge.

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:

Conflicts:
	db/db_impl.cc
	db/version_set.cc
	util/options.cc

Summary: as subject

Test Plan: run db_bench readrandom

Reviewers: dhruba

Reviewed By: dhruba

CC: MarkCallaghan, emayanke, sheki

Differential Revision: https://reviews.facebook.net/D6495

Summary:
The Version::GetOverlappingInputs() is called multiple times in
the compaction code path. Eack invocation does a binary search
for overlapping files in the specified key range.
This patch remembers the offset of an overlapped file when
GetOverlappingInputs() is called the first time within
a compaction run. Suceeding calls to GetOverlappingInputs()
uses the remembered index to avoid the binary search.

I measured that 1000 iterations of GetOverlappingInputs
takes around 4500 microseconds without this patch. If I use
this patch with the hint on every invocation, then 1000
iterations take about 3900 microsecond.

Test Plan: make check OPT=-g

Reviewers: heyongqiang

Reviewed By: heyongqiang

CC: MarkCallaghan, emayanke, sheki

Differential Revision: https://reviews.facebook.net/D6513

Summary:
Added a conditional flush in ~DBImpl to flush.
There is still a chance of writes not being persisted if there is a
crash (not a clean shutdown) before the DBImpl instance is destroyed.

Test Plan: modified db_test to meet the new expectations.

Reviewers: dhruba, heyongqiang

Differential Revision: https://reviews.facebook.net/D6519

Summary:
The default compilation process now uses "-Wall" to compile.
Fix all compilation error generated by gcc.

Test Plan: make all check

Reviewers: heyongqiang, emayanke, sheki

Reviewed By: heyongqiang

CC: MarkCallaghan

Differential Revision: https://reviews.facebook.net/D6525

Conflicts:
	db/version_set.cc
	util/options.cc

Summary:
The method Version::GetOverlappingInputs used a sequential search
to map a kay-range to a set of files. But the files are arranged
in ascending order of key, so a biary search is more effective.

This patch implements Version::GetOverlappingInputsBinarySearch
that finds one file that corresponds to the specified key range
and then iterates backwards and forwards to find all overlapping
files.

This patch is critical for making compactions efficient, especially
when there are thousands of files in a single level.

I measured that 1000 iterations of TEST_MaxNextLevelOverlappingBytes
takes 16000 microseconds without this patch. With this patch, the
same method takes about 4600 microseconds.

Test Plan: Almost all unit tests in db_test uses this method to lookup keys.

Reviewers: heyongqiang

Reviewed By: heyongqiang

CC: MarkCallaghan, emayanke, sheki

Differential Revision: https://reviews.facebook.net/D6465

Summary:
There are certain use-cases where the application intends to
delete older keys aftre they have expired a certian time period.
One option for those applications is to periodically scan the
entire database and delete appropriate keys.

A better way is to allow the application to hook into the
compaction process. This patch allows the application to set
a method callback for every key that is being compacted. If
this method returns true, then the key is not preserved in
the output of the compaction.

Test Plan:
This is mostly to preview the proposed new public api.
Since it is a public api, please do due diligence on reviewing it.

I will be writing test cases for this api in mynext version of
this patch.

Reviewers: MarkCallaghan, heyongqiang

Reviewed By: heyongqiang

CC: sheki, adsharma

Differential Revision: https://reviews.facebook.net/D6285