Commit Graph

594 Commits

Author SHA1 Message Date
Naman Gupta
8454cfe569 Add read/modify/write functionality to Put() api
Summary: The application can set a callback function, which is applied on the previous value. And calculates the new value. This new value can be set, either inplace, if the previous value existed in memtable, and new value is smaller than previous value. Otherwise the new value is added normally.

Test Plan: fbmake. Added unit tests. All unit tests pass.

Reviewers: dhruba, haobo

Reviewed By: haobo

CC: sdong, kailiu, xinyaohu, sumeet, leveldb

Differential Revision: https://reviews.facebook.net/D14745
2014-01-14 07:55:16 -08:00
Igor Canadi
dd6ecdf342 Use ASSERT_EQ() instead of assert() in merge_test 2014-01-11 09:25:47 -08:00
Schalk-Willem Kruger
a09ee1069d Improve RocksDB "get" performance by computing merge result in memtable
Summary:
Added an option (max_successive_merges) that can be used to specify the
maximum number of successive merge operations on a key in the memtable.
This can be used to improve performance of the "get" operation. If many
successive merge operations are performed on a key, the performance of "get"
operations on the key deteriorates, as the value has to be computed for each
"get" operation by applying all the successive merge operations.

FB Task ID: #3428853

Test Plan:
make all check
db_bench --benchmarks=readrandommergerandom
counter_stress_test

Reviewers: haobo, vamsi, dhruba, sdong

Reviewed By: haobo

CC: zshao

Differential Revision: https://reviews.facebook.net/D14991
2014-01-10 17:33:56 -08:00
Siying Dong
aa0ef6602d [Performance Branch] If options.max_open_files set to be -1, cache table readers in FileMetadata for Get() and NewIterator()
Summary:
In some use cases, table readers for all live files should always be cached. In that case, there will be an opportunity to avoid the table cache look-up while Get() and NewIterator().

We define options.max_open_files = -1 to be the mode that table readers for live files will always be kept. In that mode, table readers are cached in FileMetaData (with a reference count hold in table cache). So that when executing table_cache.Get() and table_cache.newInterator(), LRU cache checking can be by-passed, to reduce latency.

Test Plan: add a test case in db_test

Reviewers: haobo, kailiu

Reviewed By: haobo

CC: dhruba, igor, leveldb

Differential Revision: https://reviews.facebook.net/D15039
2014-01-10 15:57:49 -08:00
Siying Dong
5b5ab0c1a8 [Performance Branch] Fix memory leak in HashLinkListRep.GetIterator()
Summary: Full list constructed for full iterator can be leaked. This was a bug introduced when I copy the full iterator codes from hash skip list to hash link list. This patch fixes it.

Test Plan: Run valgrind test against db_test and make sure the memory leak is fixed

Reviewers: kailiu, haobo

Reviewed By: kailiu

CC: igor, leveldb

Differential Revision: https://reviews.facebook.net/D15093
2014-01-10 12:12:28 -08:00
Siying Dong
237a3da677 StopWatch not to get time if it is created for statistics and it is disabled
Summary: Currently, even if statistics is not enabled, StopWatch only for the stats still gets the time of the day, which is wasteful. This patch adds a new option to StopWatch to disable this get in this case.

Test Plan: make all check

Reviewers: dhruba, haobo, igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14703

Conflicts:
	db/db_impl.cc
2014-01-09 17:39:48 -08:00
Siying Dong
424a524ac9 [Performance Branch] A Hashed Linked List Based Mem Table
Summary:
Implement a mem table, in which keys are hashed based on prefixes. In each bucket, entries are organized in a sorted linked list. It has the same thread safety guarantee as skip list.

The motivation is to optimize memory usage for the case that prefix hashing is primary way of seeking to the entry. Compared to hash skip list implementation, this implementation is more memory efficient, but inside each bucket, search is always linear. The target scenario is that there are only very limited number of records in each hash bucket.

Test Plan: Add a test case in db_test

Reviewers: haobo, kailiu, dhruba

Reviewed By: haobo

CC: igor, nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D14979
2014-01-09 16:19:11 -08:00
Siying Dong
5575316350 StopWatch not to get time if it is created for statistics and it is disabled
Summary: Currently, even if statistics is not enabled, StopWatch only for the stats still gets the time of the day, which is wasteful. This patch adds a new option to StopWatch to disable this get in this case.

Test Plan: make all check

Reviewers: dhruba, haobo, igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14703
2014-01-08 16:05:36 -08:00
Mark Callaghan
50994bf699 Don't always compress L0 files written by memtable flush
Summary:
Code was always compressing L0 files written by a memtable flush
when compression was enabled. Now this is done when
min_level_to_compress=0 for leveled compaction and when
universal_compaction_size_percent=-1 for universal compaction.

Task ID: #3416472

Blame Rev:

Test Plan:
ran db_bench with compression options

Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: dhruba, igor, sdong

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14757
2014-01-07 21:50:26 -08:00
Igor Canadi
a45b7d83ba Merge pull request #59 from mlin/more-c-bindings
C API: add rocksdb_env_set_high_priority_background_threads
2014-01-07 16:33:03 -08:00
Igor Canadi
17a222670b Merge branch 'master' into performance 2014-01-07 11:04:21 -08:00
Tomislav Novak
9f690ec62c Fix a deadlock in CompactRange()
Summary:
The way DBImpl::TEST_CompactRange() throttles down the number of bg compactions
can cause it to deadlock when CompactRange() is called concurrently from
multiple threads. Imagine a following scenario with only two threads
(max_background_compactions is 10 and bg_compaction_scheduled_ is initially 0):

   1. Thread #1 increments bg_compaction_scheduled_ (to LargeNumber), sets
      bg_compaction_scheduled_ to 9 (newvalue), schedules the compaction
      (bg_compaction_scheduled_ is now 10) and waits for it to complete.
   2. Thread #2 calls TEST_CompactRange(), increments bg_compaction_scheduled_
      (now LargeNumber + 10) and waits on a cv for bg_compaction_scheduled_ to
      drop to LargeNumber.
   3. BG thread completes the first manual compaction, decrements
      bg_compaction_scheduled_ and wakes up all threads waiting on bg_cv_.
      Thread #1 runs, increments bg_compaction_scheduled_ by LargeNumber again
      (now 2*LargeNumber + 9). Since that's more than LargeNumber + newvalue,
      thread #2 also goes to sleep (waiting on bg_cv_), without resetting
      bg_compaction_scheduled_.

This diff attempts to address the problem by introducing a new counter
bg_manual_only_ (when positive, MaybeScheduleFlushOrCompaction() will only
schedule manual compactions).

Test Plan:
I could pretty much consistently reproduce the deadlock with a program that
calls CompactRange(nullptr, nullptr) immediately after Write() from multiple
threads. This no longer happens with this patch.

Tests (make check) pass.

Reviewers: dhruba, igor, sdong, haobo

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14799
2014-01-07 10:37:34 -08:00
Kai Liu
5e7d5629c7 Fix the valgrind issues 2014-01-03 11:48:31 -08:00
Kai Liu
774ed89c24 Replace vector with autovector
Summary: this diff only replace the cases when we need to frequently create vector with small amount of entries. This diff doesn't aim to improve performance of a specific area, but more like a small scale test for the autovector and see how it works in real life.

Test Plan:
make check

I also ran the performance tests, however there is no performance gain/loss. All performance numbers are pretty much the same before/after the change.

Reviewers: dhruba, haobo, sdong, igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14985
2014-01-02 16:43:35 -08:00
kailiu
e72aa37cc5 Merge branch 'master' into performance
Conflicts:
	db/table_cache.cc
2014-01-02 16:34:59 -08:00
kailiu
476416c27c Some minor refactoring on the code
Summary: I made some cleanup while reading the source code in `db`. Most changes are about style, naming or C++ 11 new features.

Test Plan: ran `make check`

Reviewers: haobo, dhruba, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15009
2014-01-02 16:32:31 -08:00
kailiu
9281a826f1 Hotfix the bug in table cache's GetSliceForFileNumber
Forgot to fix this problem in master branch. Already fixed it in performance branch.
2014-01-02 10:30:42 -08:00
Igor Canadi
b60c14f6ee Support multi-threaded DisableFileDeletions() and EnableFileDeletions()
Summary:
We don't want two threads to clash if they concurrently call DisableFileDeletions() and EnableFileDeletions(). I'm adding a counter that will enable file deletions only after all DisableFileDeletions() calls have been negated with EnableFileDeletions().

However, we also don't want to break the old behavior, so I added a parameter force to EnableFileDeletions(). If force is true, we will still enable file deletions after every call to EnableFileDeletions(), which is what is happening now.

Test Plan: make check

Reviewers: dhruba, haobo, sanketh

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14781
2014-01-02 03:33:42 -08:00
Mike Lin
4b1d049236 C API: add rocksdb_env_set_high_priority_background_threads 2013-12-31 15:14:18 -08:00
kailiu
f1cec73a76 Merge branch 'master' into performance
Conflicts:
	db/db_impl.cc
	db/db_test.cc
	db/memtable.cc
	db/version_set.cc
	include/rocksdb/statistics.h
2013-12-27 12:23:17 -08:00
Siying Dong
a094f3b3b5 TableCache.FindTable() to avoid the mem copy of file number
Summary: I'm not sure what's the purpose of encoding file number to a new buffer for looking up the table cache. It seems to be unnecessary to me. With this patch, we point the lookup key to the address of the int64 of the file number.

Test Plan: make all check

Reviewers: dhruba, haobo, igor, kailiu

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14811
2013-12-26 16:57:07 -08:00
Siying Dong
18df47b79a Avoid malloc in NotFound key status if no message is given.
Summary:
In some places we have NotFound status created with empty message, but it doesn't avoid a malloc. With this patch, the malloc is avoided for that case.

The motivation of it is that I found in db_bench readrandom test when all keys are not existing, about 4% of the total running time is spent on malloc of Status, plus a similar amount of CPU spent on free of them, which is not necessary.

Test Plan: make all check

Reviewers: dhruba, haobo, igor

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14691
2013-12-26 16:23:10 -08:00
kailiu
079a21ba99 Fix the unused variable warning message in mac os 2013-12-26 15:12:30 -08:00
Haobo Xu
bf4a48ccb3 [RocksDB] [Performance Branch] Revert previous patch.
Summary: The previous patch is wrong. rep_.resize(kHeader) just resets the header portion to zero, and should not cause a re-allocation if g++ does it right. I will go ahead and revert it.

Test Plan: make check

Reviewers: dhruba, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14793
2013-12-20 18:20:06 -08:00
Haobo Xu
e94eea4527 [RocksDB] [Performance Branch] Minor fix, Remove string resize from WriteBatch::Clear
Summary: tmp_batch_ will get re-allocated for every merged write batch because of the existing resize in WriteBatch::Clear. Note that in DBImpl::BuildBatchGroup, we have a hard coded upper limit of batch size 1<<20 = 1MB already.

Test Plan: make check

Reviewers: dhruba, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14787
2013-12-20 16:29:05 -08:00
Siying Dong
abaf26266d [RocksDB] [Performance Branch] Some Changes to PlainTable format
Summary:
Some changes to PlainTable format:
(1) support variable key length
(2) use user defined slice transformer to extract prefixes
(3) Run some test cases against PlainTable in db_test and table_test

Test Plan: test db_test

Reviewers: haobo, kailiu

CC: dhruba, igor, leveldb, nkg-

Differential Revision: https://reviews.facebook.net/D14457
2013-12-20 12:08:35 -08:00
Igor Canadi
1fdb3f7dc6 [RocksDB] Optimize locking for Get
Summary:
Instead of locking and saving a DB state, we can cache a DB state and update it only when it changes. This change reduces lock contention and speeds up read operations on the DB.

Performance improvements are substantial, although there is some cost in no-read workloads. I ran the regression tests on my devserver and here are the numbers:

  overwrite                    56345  ->   63001
  fillseq                      193730 ->  185296
  readrandom                   771301 -> 1219803 (58% improvement!)
  readrandom_smallblockcache   677609 ->  862850
  readrandom_memtable_sst      710440 -> 1109223
  readrandom_fillunique_random 221589 ->  247869
  memtablefillrandom           105286 ->   92643
  memtablereadrandom           763033 -> 1288862

Test Plan:
make asan_check
I am also running db_stress

Reviewers: dhruba, haobo, sdong, kailiu

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14679
2013-12-20 09:57:58 -08:00
Mark Callaghan
ca92068b12 Add 'readtocache' test
Summary:
For some tests I want to cache the database prior to running other tests on the same invocation
of db_bench. The readtocache test ignores --threads and --reads so those can be used by other tests
and it will still do a full read of --num rows with one thread. It might be invoked like:
  db_bench --benchmarks=readtocache,readrandom --reads 100 --num 10000 --threads 8

Task ID: #

Blame Rev:

Test Plan:
run db_bench

Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14739
2013-12-18 16:54:53 -08:00
Igor Canadi
3b50b6213d Merge pull request #37 from mlin/more-c-bindings
C bindings: add a bunch of the newer options
2013-12-18 13:12:04 -08:00
Siying Dong
14995a8ff3 Move level0 sorting logic from Version::SaveTo() to Version::Finalize()
Summary: I realized that "D14409 Avoid sorting in Version::Get() by presorting them in VersionSet::Builder::SaveTo()" is not done in an optimized place. SaveTo() is usually inside mutex. Move it to Finalize(), which is called out of mutex.

Test Plan: make all check

Reviewers: dhruba, haobo, kailiu

Reviewed By: dhruba

CC: igor, leveldb

Differential Revision: https://reviews.facebook.net/D14607
2013-12-17 18:06:58 -08:00
Siying Dong
a8b8b11dc4 Get() Does Not Reserve space for to_delete memtables
Summary: It seems to be a decision tradeoff in current codes: we make a malloc for every Get() to reduce one malloc for a flush inside mutex. It takes about 5% of CPU time in readrandom tests. We might consider the tradeoff to be the other way around.

Test Plan: make all check

Reviewers: dhruba, haobo, igor

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14697
2013-12-17 17:16:16 -08:00
Mike Lin
2a2506b629 C bindings: add a bunch of the newer options 2013-12-15 13:47:06 -08:00
Kai Liu
2e9efcd6d8 Add the property block for the plain table
Summary:
This is the last diff that adds the property block to plain table.
The format resembles that of the block-based table: https://github.com/facebook/rocksdb/wiki/Rocksdb-table-format

  [data block]
  [meta block 1: stats block]
  [meta block 2: future extended block]
  ...
  [meta block K: future extended block]  (we may add more meta blocks in the future)
  [metaindex block]
  [index block: we only have the placeholder here, we can add persistent index block in the future]
  [Footer: contains magic number, handle to metaindex block and index block]
  <end_of_file>

Test Plan: extended existing property block test.

Reviewers: haobo, sdong, dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14523
2013-12-13 17:18:14 -08:00
kailiu
0cd1521af5 Completely remove argv_ since no one use it
There are still warning in some other environment, just move that useless variable `argv_`
2013-12-12 16:36:38 -08:00
kailiu
0e24f97b9f Revert last commit and add "unused" attribute to suppress warning 2013-12-12 15:40:44 -08:00
kailiu
bc9b488e92 fix a warning in db_test when running make release 2013-12-12 15:35:02 -08:00
Mark Callaghan
e9e6b00d29 Add monitoring for universal compaction and add counters for compaction IO
Summary:
Adds these counters
{ WAL_FILE_SYNCED, "rocksdb.wal.synced" }
  number of writes that request a WAL sync
{ WAL_FILE_BYTES, "rocksdb.wal.bytes" },
  number of bytes written to the WAL
{ WRITE_DONE_BY_SELF, "rocksdb.write.self" },
  number of writes processed by the calling thread
{ WRITE_DONE_BY_OTHER, "rocksdb.write.other" },
  number of writes not processed by the calling thread. Instead these were
  processed by the current holder of the write lock
{ WRITE_WITH_WAL, "rocksdb.write.wal" },
  number of writes that request WAL logging
{ COMPACT_READ_BYTES, "rocksdb.compact.read.bytes" },
  number of bytes read during compaction
{ COMPACT_WRITE_BYTES, "rocksdb.compact.write.bytes" },
  number of bytes written during compaction

Per-interval stats output was updated with WAL stats and correct stats for universal compaction
including a correct value for write-amplification. It now looks like:
                               Compactions
Level  Files Size(MB) Score Time(sec)  Read(MB) Write(MB)    Rn(MB)  Rnp1(MB)  Wnew(MB) RW-Amplify Read(MB/s) Write(MB/s)      Rn     Rnp1     Wnp1     NewW    Count  Ln-stall Stall-cnt
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  0        7      464  46.4       281      3411      3875      3411         0      3875        2.1      12.1        13.8      621        0      240      240      628       0.0         0
Uptime(secs): 310.8 total, 2.0 interval
Writes cumulative: 9999999 total, 9999999 batches, 1.0 per batch, 1.22 ingest GB
WAL cumulative: 9999999 WAL writes, 9999999 WAL syncs, 1.00 writes per sync, 1.22 GB written
Compaction IO cumulative (GB): 1.22 new, 3.33 read, 3.78 write, 7.12 read+write
Compaction IO cumulative (MB/sec): 4.0 new, 11.0 read, 12.5 write, 23.4 read+write
Amplification cumulative: 4.1 write, 6.8 compaction
Writes interval: 100000 total, 100000 batches, 1.0 per batch, 12.5 ingest MB
WAL interval: 100000 WAL writes, 100000 WAL syncs, 1.00 writes per sync, 0.01 MB written
Compaction IO interval (MB): 12.49 new, 14.98 read, 21.50 write, 36.48 read+write
Compaction IO interval (MB/sec): 6.4 new, 7.6 read, 11.0 write, 18.6 read+write
Amplification interval: 101.7 write, 102.9 compaction
Stalls(secs): 142.924 level0_slowdown, 0.000 level0_numfiles, 0.805 memtable_compaction, 0.000 leveln_slowdown
Stalls(count): 132461 level0_slowdown, 0 level0_numfiles, 3 memtable_compaction, 0 leveln_slowdown

Task ID: #3329644, #3301695

Blame Rev:

Test Plan:
Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14583
2013-12-12 13:27:43 -08:00
Siying Dong
e8ab1934d9 [RocksDB Performance Branch] DBImpl.NewInternalIterator() to reduce works inside mutex
Summary: To reduce mutex contention caused by DBImpl.NewInternalIterator(), in this function, move all the iteration creation works out of mutex, only leaving object ref and get.

Test Plan:
make all check
will run db_stress for a while too to make sure no problem.

Reviewers: haobo, dhruba, kailiu

Reviewed By: haobo

CC: igor, leveldb

Differential Revision: https://reviews.facebook.net/D14589
2013-12-12 11:30:00 -08:00
Siying Dong
aaf9c6203c [RocksDB][Performance Branch]Iterator Cleanup method only tries to find obsolete files if it has the last reference to a version
Summary: When deconstructing an iterator, no need to check obsolete file if it doesn't hold last reference of any version.

Test Plan: make all check

Reviewers: haobo, igor, dhruba, kailiu

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14595
2013-12-11 13:59:43 -08:00
Siying Dong
a8029fdc75 Introduce MergeContext to Lazily Initialize merge operand list
Summary: In get operations, merge_operands is only used in few cases. Lazily initialize it can reduce average latency in some cases

Test Plan: make all check

Reviewers: haobo, kailiu, dhruba

Reviewed By: haobo

CC: igor, nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D14415

Conflicts:
	db/db_impl.cc
	db/memtable.cc
2013-12-11 11:37:28 -08:00
Siying Dong
bc5dd19b14 [RocksDB Performance Branch] Avoid sorting in Version::Get() by presorting them in VersionSet::Builder::SaveTo()
Summary: Pre-sort files in VersionSet::Builder::SaveTo() so that when getting the value, no need to sort them. It can avoid the costs of vector operations and sorting in Version::Get().

Test Plan: make all check

Reviewers: haobo, kailiu, dhruba

Reviewed By: dhruba

CC: nkg-, igor, leveldb

Differential Revision: https://reviews.facebook.net/D14409
2013-12-11 10:50:09 -08:00
Siying Dong
41349d9ef1 [RocksDB Performance Branch] Avoid sorting in Version::Get() by presorting them in VersionSet::Builder::SaveTo()
Summary: Pre-sort files in VersionSet::Builder::SaveTo() so that when getting the value, no need to sort them. It can avoid the costs of vector operations and sorting in Version::Get().

Test Plan: make all check

Reviewers: haobo, kailiu, dhruba

Reviewed By: dhruba

CC: nkg-, igor, leveldb

Differential Revision: https://reviews.facebook.net/D14409
2013-12-11 10:49:49 -08:00
Siying Dong
0304e3d2ff When flushing mem tables, create iterators out of mutex
Summary:
creating new iterators of mem tables can be expensive. Move them out of mutex.
DBImpl::WriteLevel0Table()'s mems seems to be a local vector and is only used by flushing. memtables to flush are also immutable, so it should be safe to do so.

Test Plan: make all check

Reviewers: haobo, dhruba, kailiu

Reviewed By: dhruba

CC: igor, leveldb

Differential Revision: https://reviews.facebook.net/D14577

Conflicts:
	db/db_impl.cc
2013-12-11 10:02:17 -08:00
Siying Dong
95a411d853 When flushing mem tables, create iterators out of mutex
Summary:
creating new iterators of mem tables can be expensive. Move them out of mutex.
DBImpl::WriteLevel0Table()'s mems seems to be a local vector and is only used by flushing. memtables to flush are also immutable, so it should be safe to do so.

Test Plan: make all check

Reviewers: haobo, dhruba, kailiu

Reviewed By: dhruba

CC: igor, leveldb

Differential Revision: https://reviews.facebook.net/D14577
2013-12-11 09:57:19 -08:00
Haobo Xu
3c02c363b3 [RocksDB] [Performance Branch] Added dynamic bloom, to be used for memable non-existing key filtering
Summary: as title

Test Plan: dynamic_bloom_test

Reviewers: dhruba, sdong, kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14385
2013-12-11 00:15:14 -08:00
kailiu
a82f42b765 rename db/memtablelist.{h,cc} 2013-12-10 19:03:13 -08:00
Igor Canadi
204bb9cffd Get rid of LogFlush() in InternalIterator 2013-12-10 10:59:00 -08:00
Igor Canadi
19f5463d3f Don't LogFlush() in foreground threads
Summary: So fflush() takes a lock which is heavyweight. I added flush_pending_, but more importantly, I removed LogFlush() from foreground threads.

Test Plan: ./db_test

Reviewers: dhruba, haobo

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14535
2013-12-10 10:57:46 -08:00
Igor Canadi
a204dabb9d Merge pull request #31 from sepeth/c-api
Rename leveldb to rocksdb in C api
2013-12-10 09:18:47 -08:00
Doğan Çeçen
6c4e110c8c Rename leveldb to rocksdb in C api 2013-12-10 10:48:35 +02:00
Igor Canadi
fb9fce4fc3 [RocksDB] BackupableDB
Summary:
In this diff I present you BackupableDB v1. You can easily use it to backup your DB and it will do incremental snapshots for you.
Let's first describe how you would use BackupableDB. It's inheriting StackableDB interface so you can easily construct it with your DB object -- it will add a method RollTheSnapshot() to the DB object. When you call RollTheSnapshot(), current snapshot of the DB will be stored in the backup dir. To restore, you can just call RestoreDBFromBackup() on a BackupableDB (which is a static method) and it will restore all files from the backup dir. In the next version, it will even support automatic backuping every X minutes.

There are multiple things you can configure:
1. backup_env and db_env can be different, which is awesome because then you can easily backup to HDFS or wherever you feel like.
2. sync - if true, it *guarantees* backup consistency on machine reboot
3. number of snapshots to keep - this will keep last N snapshots around if you want, for some reason, be able to restore from an earlier snapshot. All the backuping is done in incremental fashion - if we already have 00010.sst, we will not copy it again. *IMPORTANT* -- This is based on assumption that 00010.sst never changes - two files named 00010.sst from the same DB will always be exactly the same. Is this true? I always copy manifest, current and log files.
4. You can decide if you want to flush the memtables before you backup, or you're fine with backing up the log files -- either way, you get a complete and consistent view of the database at a time of backup.
5. More things you can find in BackupableDBOptions

Here is the directory structure I use:

   backup_dir/CURRENT_SNAPSHOT - just 4 bytes holding the latest snapshot
               0, 1, 2, ... - files containing serialized version of each snapshot - containing a list of files
               files/*.sst - sst files shared between snapshots - if one snapshot references 00010.sst and another one needs to backup it from the DB, it will just reference the same file
               files/ 0/, 1/, 2/, ... - snapshot directories containing private snapshot files - current, manifest and log files

All the files are ref counted and deleted immediatelly when they get out of scope.

Some other stuff in this diff:
1. Added GetEnv() method to the DB. Discussed with @haobo and we agreed that it seems right thing to do.
2. Fixed StackableDB interface. The way it was set up before, I was not able to implement BackupableDB.

Test Plan:
I have a unittest, but please don't look at this yet. I just hacked it up to help me with debugging. I will write a lot of good tests and update the diff.

Also, `make asan_check`

Reviewers: dhruba, haobo, emayanke

Reviewed By: dhruba

CC: leveldb, haobo

Differential Revision: https://reviews.facebook.net/D14295
2013-12-09 14:06:52 -08:00
kailiu
551e9428ce Merge branch 'master' into performance 2013-12-06 14:15:42 -08:00
Siying Dong
ef2211a9ca [RocksDB Performance Branch] Introduce MergeContext to Lazily Initialize merge operand list
Summary: In get operations, merge_operands is only used in few cases. Lazily initialize it can reduce average latency in some cases

Test Plan: make all check

Reviewers: haobo, kailiu, dhruba

Reviewed By: haobo

CC: igor, nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D14415
2013-12-06 10:28:59 -08:00
kailiu
b1d2de4a40 Fix #26 by putting the implementation of CreateDBStatistics() to a cc file 2013-12-05 22:29:03 -08:00
kailiu
90729f8b23 Extract metaindex block from block-based table
Summary: This change will allow other table to reuse the code for meta blocks.

Test Plan: all existing unit tests passed

Reviewers: dhruba, haobo, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14475
2013-12-05 16:34:16 -08:00
Mayank Agarwal
92e8316118 Make GetDbIdentity pure virtual and also implement it for StackableDB, DBWithTTL
Summary: As title

Test Plan: make clean and make

Reviewers: igor

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14469
2013-12-05 12:02:31 -08:00
Mayank Agarwal
18802689b8 Make an API to get database identity from the IDENTITY file
Summary: This would enable rocksdb users to get the db identity without depending on implementation details(storing that in IDENTITY file)

Test Plan: db/db_test (has identity checks)

Reviewers: dhruba, haobo, igor, kailiu

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14463
2013-12-04 22:39:17 -08:00
Mark Callaghan
97aa401e2f Add compression options to db_bench
Summary:
This adds 2 options for compression to db_bench:
* universal_compression_size_percent
* compression_level - to set zlib compression level
It also logs compression_size_percent at startup in LOG

Task ID: #

Blame Rev:

Test Plan:
make check, run db_bench

Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14439
2013-12-03 14:28:48 -08:00
Sajal Jain
28a1b9b95f [rocksdb] statistics counters for memtable hits and misses
Summary:
added counters
rocksdb.memtable.hit - for memtable hit
rocksdb.memtable.miss - for memtable miss

Test Plan: db_bench tests

Reviewers: igor, dhruba, haobo

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D14433
2013-12-03 12:59:53 -08:00
Igor Canadi
eb12e47e0e Killing Transform Rep
Summary:
Let's get rid of TransformRep and it's children. We have confirmed that HashSkipListRep works better with multifeed, so there is no benefit to keeping this around.

This diff is mostly just deleting references to obsoleted functions. I also have a diff for fbcode that we'll need to push when we switch to new release.

I had to expose HashSkipListRepFactory in the client header files because db_impl.cc needs access to GetTransform() function for SanitizeOptions.

Test Plan: make check

Reviewers: dhruba, haobo, kailiu, sdong

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14397
2013-12-03 12:42:15 -08:00
Igor Canadi
043fc14c3e Get rid of some shared_ptrs
Summary:
I went through all remaining shared_ptrs and removed the ones that I found not-necessary. Only GenerateCachePrefix() is called fairly often, so don't expect much perf wins.

The ones that are left are accessed infrequently and I think we're fine with keeping them.

Test Plan: make asan_check

Reviewers: dhruba, haobo

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14427
2013-12-03 11:17:58 -08:00
Dhruba Borthakur
96bc3ec297 Memtables should be deleted appropriately in the unit test.
Summary:
Memtables should be deleted appropriately in the unit test.

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:
2013-12-01 21:23:44 -08:00
Dhruba Borthakur
98968ba937 Free obsolete memtables outside the dbmutex had a memory leak.
Summary:
The commit at 27bbef1180 had a memory leak
that was detected by valgrind. The memtable that has a refcount decrement
in MemTableList::InstallMemtableFlushResults was not freed.

Test Plan: valgrind ./db_test --leak-check=full

Reviewers: igor

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14391
2013-11-28 10:25:22 -08:00
Igor Canadi
35ddf18367 Don't do compression tests if we don't have compression libs
Summary: These tests fail if compression libraries are not installed.

Test Plan: Manually disabled snappy, observed tests not ran.

Reviewers: dhruba, kailiu

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14379
2013-11-27 13:32:56 -08:00
Kai Liu
1966b63137 Merge branch 'master' into perf 2013-11-27 11:47:40 -08:00
Haobo Xu
4e6463ea44 [RocksDB][Performance Branch] Make height and branching factor configurable for skiplist implementation
Summary: As title. Especially, HashSkipListRepFactory will be able to specify a relatively small height, to reduce the memory overhead of one skiplist per bucket.

Test Plan: make check and test it on leaf4

Reviewers: dhruba, sdong, kailiu

CC: reconnect.grayhat, leveldb

Differential Revision: https://reviews.facebook.net/D14307
2013-11-26 21:59:36 -08:00
Dhruba Borthakur
8478f380a0 During benchmarking, I see excessive use of vector.reserve().
Summary:
This code path can potentially accumulate multiple important_files for level 0.
But for other levels, it should have only one file in the
important_files, so it is ok not to reserve excessive space, is it not?

Test Plan: make check

Reviewers: haobo

Reviewed By: haobo

CC: reconnect.grayhat, leveldb

Differential Revision: https://reviews.facebook.net/D14349
2013-11-26 07:47:08 -08:00
Dhruba Borthakur
27bbef1180 Free obsolete memtables outside the dbmutex.
Summary:
Large memory allocations and frees are costly and best done outside the
db-mutex. The memtables are already allocated outside the db-mutex but
they were being freed while holding the db-mutex.
This patch frees obsolete memtables outside the db-mutex.

Test Plan:
make check
db_stress

Unit tests pass, I am in the process of running stress tests.

Reviewers: haobo, igor, emayanke

Reviewed By: haobo

CC: reconnect.grayhat, leveldb

Differential Revision: https://reviews.facebook.net/D14319
2013-11-25 21:04:48 -08:00
Igor Canadi
3ce3658411 DB::GetOptions()
Summary: We need access to options for BackupableDB

Test Plan: make check

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb, reconnect.grayhat

Differential Revision: https://reviews.facebook.net/D14331
2013-11-25 15:51:50 -08:00
Igor Canadi
11c26bd4a4 [RocksDB] Interface changes required for BackupableDB
Summary: This is part of https://reviews.facebook.net/D14295 -- smaller diff that is easier to review

Test Plan: make asan_check

Reviewers: dhruba, haobo, emayanke

Reviewed By: emayanke

CC: leveldb, kailiu, reconnect.grayhat

Differential Revision: https://reviews.facebook.net/D14301
2013-11-25 12:39:23 -08:00
Dhruba Borthakur
299f5c76bb Create new log file outside the dbmutex.
Summary:
All filesystem Io should be done outside the dbmutex. There was one place
when we have to roll the transaction log that we were creating the new log file
while holding the dbmutex.

I rearranged this code so that the act of creating the new transaction log
file is done without holding the dbmutex.  I also allocate the new memtable
outside the dbmutex, this is important because creating the memtable
could be heavyweight.

Test Plan: make check and dbstress

Reviewers: haobo, igor

Reviewed By: haobo

CC: leveldb, reconnect.grayhat

Differential Revision: https://reviews.facebook.net/D14283
2013-11-25 11:23:42 -08:00
Haobo Xu
5b825d6964 [RocksDB] Use raw pointer instead of shared pointer when passing Statistics object internally
Summary: liveness of the statistics object is already ensured by the shared pointer in DB options. There's no reason to pass again shared pointer among internal functions. Raw pointer is sufficient and efficient.

Test Plan: make check

Reviewers: dhruba, MarkCallaghan, igor

Reviewed By: dhruba

CC: leveldb, reconnect.grayhat

Differential Revision: https://reviews.facebook.net/D14289
2013-11-25 10:38:15 -08:00
Siying Dong
718488abc5 Add BloomFilter to PlainTableIterator::Seek()
Summary:
This patch adds a simple bloom filter in PlainTableIterator::Seek()

Test Plan: N/A

Reviewers:

CC:

Task ID: #

Blame Rev:
2013-11-21 22:26:39 -08:00
kailiu
0c93df912e Improve the readability of the TableProperties::ToString() 2013-11-21 17:54:23 -08:00
Siying Dong
3e35aa6412 Revert "Allow users to profile a query and see bottleneck of the query"
This reverts commit 3d8ac31d71.
2013-11-21 17:40:39 -08:00
Siying Dong
b135d01e7b Allow users to profile a query and see bottleneck of the query
Summary:
Provide a framework to profile a query in detail to figure out latency bottleneck. Currently, in Get(), Put() and iterators, 2-3 simple timing is used. We can easily add more profile counters to the framework later.

Test Plan: Enable this profiling in seveal existing tests.

Reviewers: haobo, dhruba, kailiu, emayanke, vamsi, igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14001

Conflicts:
	table/merger.cc
2013-11-21 17:39:19 -08:00
Siying Dong
3d8ac31d71 Allow users to profile a query and see bottleneck of the query
Summary:
Provide a framework to profile a query in detail to figure out latency bottleneck. Currently, in Get(), Put() and iterators, 2-3 simple timing is used. We can easily add more profile counters to the framework later.

Test Plan: Enable this profiling in seveal existing tests.

Reviewers: haobo, dhruba, kailiu, emayanke, vamsi, igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14001
2013-11-21 16:29:57 -08:00
Siying Dong
58e1956d50 [Only for Performance Branch] A Hacky patch to lazily generate memtable key for prefix-hashed memtables.
Summary:
For prefix mem tables, encoding mem table key may be unnecessary if the prefix doesn't have any key. This patch is a little bit hacky but I want to try out the performance gain of removing this lazy initialization.

In longer term, we might want to revisit the way we abstract mem tables implementations.

Test Plan: make all check

Reviewers: haobo, igor, kailiu

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14265
2013-11-20 20:49:23 -08:00
Siying Dong
b59d4d5a50 A Simple Plain Table
Summary:
A Simple plain table format. No block structure. When creating the table reader, scanning the full table to create indexes.

Test Plan:Add unit test

Reviewers:haobo,dhruba,kailiu

CC:

Task ID: #

Blame Rev:
2013-11-20 18:44:22 -08:00
Siying Dong
071fb0d77b Inline a couple of functions and put one save lazily clearing
Summary:
Machine several functions inline.
Also, in DBIter.Seek() make value cleaning up lazily done.
These are for the use case that Seek() are called lots of times but few return values.

Test Plan: make all check

Differential Revision: https://reviews.facebook.net/D14217
2013-11-20 17:32:57 -08:00
Haobo Xu
37b459f0aa [RocksDB] Test diff on performance branch
Summary: trivia comment change

Test Plan: Go through the step ofs developing under the performance branch

Reviewers: dhruba, kailiu, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14259
2013-11-20 14:34:52 -08:00
Haobo Xu
a617227a36 [RocksDB] fix prefix_test
Summary: user comparator needs to work if either input is prefix only.

Test Plan: ./prefix_test --write_buffer_size=100000 --total_prefixes=10000 --items_per_prefix=10

Reviewers: dhruba, igor

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14241
2013-11-20 09:16:23 -08:00
kailiu
6eb5649800 Move flush_block_policy from Options to TableFactory
Summary:
Previously we introduce a `flush_block_policy_factory` in Options, however, that options is strongly releated to Table based tables.
It will make more sense to move it to block based table's own factory class.

Test Plan: make check to pass existing tests

Reviewers: dhruba, haobo

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14211
2013-11-19 22:00:48 -08:00
kailiu
1415f8820d Improve the "table stats"
Summary:
The primary motivation of the changes is to make it easier to figure out the inside of the tables.

* rename "table stats" to "table properties" since now we have more than "integers" to store in the property block.
* Add filter block size to the basic table properties.
* Whenever a table is built, we'll log the table properties (the sample output is in Test Plan).
* Make an api to expose deleted keys.

Test Plan:
Passed all existing test. and the sample output of table stats:

    ==================================================================
        Basic Properties
    ------------------------------------------------------------------
                  # data blocks: 1
                      # entries: 1

                   raw key size: 9
           raw average key size: 9
                 raw value size: 9
         raw average value size: 0

                data block size: 25
               index block size: 27
              filter block size: 18
         (estimated) table size: 70

                  filter policy: rocksdb.BuiltinBloomFilter
    ==================================================================
        User collected properties: InternalKeyPropertiesCollector
    ------------------------------------------------------------------
                    kDeletedKeys: 1
    ==================================================================

Reviewers: dhruba, haobo

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14187
2013-11-19 16:29:42 -08:00
Igor Canadi
fc61428288 Include <unistd.h> in db_test
Summary: This is the only compile issue in Ubuntu. It might be better to include <unistd.h> only in env_posix and add Truncate function to Env, but since we use truncate only in db_test, I don't think it makes much sense.

Test Plan: Rocksdb now compiles on Ubuntu!

Reviewers: dhruba, kailiu

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14127
2013-11-17 21:58:16 -08:00
Igor Canadi
de9ce7d439 Upgrading compiler to gcc4.8.1
Summary:
Finally did it - the trick was in using --dynamic-linker option. This is first step to running ASAN.

All of our code seems to compile just fine on 4.8.1. However, I still left fbcode.471.sh in the 'build_tools/' just in case.

Test Plan: make clean; make

Reviewers: dhruba, haobo, kailiu, emayanke, sdong

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14109
2013-11-17 13:52:55 -08:00
Kai Liu
75df72f2a5 Change the logic in KeyMayExist()
Summary:
Previously in KeyMayExist(), if DB::Get() returns non-Status::OK(), we assumes key may not exist.
However, as if index block is not in block cache, Status::Incomplete() will return. Worse still, if
options::filter_delete is enabled, we may falsely ignore the "delete" operation:

  https://github.com/facebook/rocksdb/blob/master/db/write_batch.cc#L217-L220

This diff fixes this bug and will let crash-test pass.

Test Plan:
Ran:

  ./db_stress --test_batches_snapshots=1 --ops_per_thread=1000000 --threads=32 --write_buffer_size=4194304 --destroy_db_initially=1 --reopen=0 --readpercent=5 --prefixpercent=45 --writepercent=35 --delpercent=5 --iterpercent=10 --db=/home/kailiu/local/newer --max_key=100000000 --disable_seek_compaction=0 --mmap_read=0 --block_size=16384 --cache_size=1048576 --open_files=500000 --verify_checksum=1 --sync=0 --disable_wal=0 --disable_data_sync=0 --target_file_size_base=2097152
--target_file_size_multiplier=2 --max_write_buffer_number=3 --max_background_compactions=20 --max_bytes_for_level_base=10485760 --filter_deletes=1

Previously we'll see crash happens very soon.

Reviewers: igor, dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14115
2013-11-17 01:00:34 -08:00
kailiu
97d8e573a6 make util/env_posix.cc work under mac
Summary: This diff invoves some more complicated issues in the posix environment.

Test Plan: works under mac os. will need to verify dev box.

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14061
2013-11-16 23:44:39 -08:00
Pascal Borreli
443e04e62d Fixed typos 2013-11-16 11:21:34 +00:00
Igor Canadi
21905dd4a8 Start DeleteFileTest with clean plate
Summary:
Remove all the files from the test dir before the test. The test failed when there were some old files still in the directory, since it checks the file counts.
This is what caused jenkins' test failures. It was running fine on my machine so it was hard to repro.

Test Plan:
1. create an extra 000001.log file in the test directory
2. run a ./deletefile_test - test failes
3. patch ./deletefile_test with this
4. test succeeds

Reviewers: haobo, dhruba

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14097
2013-11-15 16:30:23 -08:00
Igor Canadi
29c931f70b Avoid populating live set if we don't need to
Summary: Also changed some comments

Test Plan: ./deletefile_test

Reviewers: haobo

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14091
2013-11-14 22:42:02 -08:00
Igor Canadi
a0ce3fd00a PurgeObsoleteFiles() unittest
Summary:
Created a unittest that verifies that automatic deletion performed by PurgeObsoleteFiles() works correctly.

Also, few small fixes on the logic part -- call version_set_->GetObsoleteFiles() in FindObsoleteFiles() instead of on some arbitrary positions.

Test Plan: Created a unit test

Reviewers: dhruba, haobo, nkg-

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14079
2013-11-14 18:03:57 -08:00
Vamsi Ponnekanti
94dde686bb [Merge operand meant for key K is being applied on wrong key]
Summary:
We iterate until we find a different key than original key.
ikey is pointing to next key when we break out of loop.
After the loop we apply all merge operands meant for original key
on the next key!

Test Plan:
Need to give a build to Marcin to test out.

Revert Plan: OK

Task ID: #3181932

Reviewers: haobo, emayanke, dhruba

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14073
2013-11-14 17:13:24 -08:00
Igor Canadi
fda8142f29 Delete log files in the correct dir
Summary: Log files are stored in wal_dir, not dbname_

Test Plan: deletfile_test

Reviewers: nkg-

Reviewed By: nkg-

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14067
2013-11-13 14:54:54 -08:00
Kai Liu
88ba331c1a Add the index/filter block cache
Summary: This diff leverage the existing block cache and extend it to cache index/filter block.

Test Plan:
Added new tests in db_test and table_test

The correctness is checked by:

1. make check
2. make valgrind_check

Performance is test by:

1. 10 times of build_tools/regression_build_test.sh on two versions of rocksdb before/after the code change. Test results suggests no significant difference between them. For the two key operatons `overwrite` and `readrandom`, the average iops are both 20k and ~260k, with very small variance).
2. db_stress.

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb, haobo, xjin

Differential Revision: https://reviews.facebook.net/D13167
2013-11-12 22:46:51 -08:00
Kai Liu
35460ccb53 Fix the string format issue
Summary:

mac and our dev server has totally differnt definition of uint64_t, therefore fixing the warning in mac has actually made code in linux uncompileable.

Test Plan:

make clean && make -j32
2013-11-12 21:05:39 -08:00
Igor Canadi
d88d8ecf80 Fix deleting files
Summary: One more fix! In some cases, our filenames start with "/". Apparently, env_ can't handle filenames with double //

Test Plan:
deletefile_test does not include this line in the LOG anymore:
2013/11/12-18:11:43.150149 7fe4a6fff700 RenameFile logfile #3 FAILED -- IO error: /tmp/rocksdbtest-3574/deletefile_test//000003.log: No such file or directory

Reviewers: dhruba, haobo

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14055
2013-11-12 20:32:07 -08:00
kailiu
21587760b9 Fixing the warning messages captured under mac os # Consider using git commit -m 'One line title' && arc diff. # You will save time by running lint and unit in the background.
Summary: The work to make sure mac os compiles rocksdb is not completed yet. But at least we can start cleaning some warnings captured only by g++ from mac os..

Test Plan: ran make in mac os

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14049
2013-11-12 20:05:28 -08:00
Igor Canadi
9df2b217e9 Move fast and break things
Summary:
Broke the compile when I removed purge_log_after_memtable_flush.

sorrybus

Test Plan: make db_bench works now

Reviewers: haobo

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14037
2013-11-12 12:42:42 -08:00
Igor Canadi
9bc4a26f56 Small changes in Deleting obsolete files
Summary:
@haobo's suggestions from https://reviews.facebook.net/D13827

Renaming some variables, deprecating purge_log_after_flush, changing for loop into auto for loop.

I have not implemented deleting objects outside of mutex yet because it would require a big code change - we would delete object in db_impl, which currently does not know anything about object because it's defined in version_edit.h (FileMetaData). We should do it at some point, though.

Test Plan: Ran deletefile_test

Reviewers: haobo

Reviewed By: haobo

CC: leveldb, haobo

Differential Revision: https://reviews.facebook.net/D14025
2013-11-12 11:53:26 -08:00