Commit graph

1781 commits

Author SHA1 Message Date
sdong ac2b9367fe Fix a typo in variable
Summary: Typo seqeuntial -> sequential in db/fault_injection_test.cc

Test Plan: Build it

Reviewers: ott, igor, anthony, kradhakrishnan, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D42417
2015-07-16 12:17:24 -07:00
sdong 6c0c8dee7b Fix data loss after DB recovery by not allowing flush/compaction to be scheduled until DB opened
Summary:
Previous run may leave some SST files with higher file numbers than manifest indicates.
Compaction or flush may start to run while DB::Open() is still going on. SST file garbage collection may happen interleaving with compaction or flush, and overwrite files generated by compaction of flushes after they are generated. This might cause data loss. This possibility of interleaving is recently introduced.
Fix it by not allowing compaction or flush to be scheduled before DB::Open() finishes.

Test Plan: Add a unit test. This verification will have a chance to fail without the fix but doesn't fix without the fix.

Reviewers: kradhakrishnan, anthony, yhchiang, IslamAbdelRahman, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42399
2015-07-16 10:57:41 -07:00
Andres Notzli e4af3bfb27 Test for compaction of corrupted keys
Summary:
Fixes T7697334. Adds a simple test to check whether CompactionJob deals
with corrupted keys correctly. Right now, we preserve corrupted keys.
Note: depending on the type of corruption and options like comparators,
CompactionJob fails. This test just checks whether corrupted keys that
do not fail CompactionJob are preserved.

Test Plan:
`make compaction_job_test && ./compaction_job_test` -> Tests pass.
Add `input->Next(); continue;` in CompactionJob::ProcessKeyValueCompaction()
inside then-branch of `!ParseInternalKey(key, &ikey)` -> Tests fail.

Reviewers: sdong, rven, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42237
2015-07-16 09:18:35 -07:00
agiardullo 81d072623c move convenience.h out of utilities
Summary: Moved convenience.h out of utilities to remove a dependency on utilities in db.

Test Plan: unit tests.  Also compiled a link to the old location to verify the _Pragma works.

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42201
2015-07-15 14:51:51 -07:00
Poornima Chozhiyath Raman beb19ad0dd Fixing delete files in Trivial move of universal compaction
Summary:
Trvial move in universal compaction was failing when trying to move files from levels other than 0.
This was because the DeleteFile while trivially moving, was only deleting files of level 0 which caused duplication of same file in different levels.
This is fixed by passing the right level as argument in the call of DeleteFile while doing trivial move.

Test Plan: ./db_test ran successfully with the new test cases.

Reviewers: sdong

Reviewed By: sdong

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D42135
2015-07-15 12:28:22 -07:00
krad c613960690 Build fix.
Summary: gcc-4.9-glibc-2.20 complains about uninitialized variable.

db/compaction_picker.cc: In member function 'bool
rocksdb::CompactionPicker::IsInputNonOverlapping(rocksdb::Compaction*)':
db/compaction_picker.cc:1174:17: error:
'prev.rocksdb::{anonymous}::InputFileInfo::f' may be used uninitialized in this
function [-Werror=maybe-uninitialized]
   InputFileInfo prev, curr, next;

Test Plan: pmake on local environment

Reviewers: sdong igor

CC: leveldb@

Task ID: #

Blame Rev:
2015-07-15 11:25:10 -07:00
Aaron Feldman 2c8de0ecae Update --help message in db_bench.
Summary:
Remove --help entry for readhot.

Update read_random_exp_range flag description: The distribution is num *
exp(-r), not num * exp(r).

Test Plan: Run ./db_bench --help

Reviewers: sdong, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D42303
2015-07-15 10:21:09 -07:00
Andres Notzli 6b2d44b2ff Refactoring of writing key/value pairs
Summary:
Before, writing key/value pairs out to files was done inside
ProcessKeyValueCompaction(). To make ProcessKeyValueCompaction()
more understandable, this patch moves the writing part to a separate
function. This is intended to be a stepping stone for additional
changes.

Test Plan: make && make check

Reviewers: sdong, rven, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42243
2015-07-15 09:55:45 -07:00
Igor Canadi 9a6a0bd8c9 Style fix in compaction_job.cc
Summary: I didn't know this can work :)

Test Plan: none

Reviewers: sdong, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42081
2015-07-15 09:36:47 +02:00
Andres Notzli ddad40e930 Fixed nullptr deref and added assert
Summary:
Fixes two minor issues in CompactionJob.
CompactionJob::Run() dereferences log_buffer_ without a check, so
this patch adds an assert in the constructor where log_buffer_
is assigned. compaction_job_stats_ can be null but
ProcessKeyValueCompaction was dereferencing it without a check.

Test Plan: make && make check

Reviewers: sdong, rven, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42231
2015-07-14 23:12:34 -07:00
Yueh-Hsuan Chiang 801df912af Move UniversalCompaction related db-tests to db_universal_compaction_test.cc
Summary: Move UniversalCompaction related db-tests to db_universal_compaction_test.cc

Test Plan:
db_test
db_universal_compaction_test

Reviewers: igor, sdong, IslamAbdelRahman, anthony

Reviewed By: anthony

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42225
2015-07-14 18:24:45 -07:00
Yueh-Hsuan Chiang 3ca6b2541e Move TailingIterator tests from db_test.cc to db_test_tailing_iterator.cc
Summary: Move TailingIterator tests from db_test.cc to db_test_tailing_iterator.cc

Test Plan:
db_test
db_test_tailing_iterator

Reviewers: igor, anthony, IslamAbdelRahman, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D42021
2015-07-14 16:41:08 -07:00
Yueh-Hsuan Chiang ce829c77e3 Make TransactionLogIterator related tests from db_test.cc to db_log_iter_test.cc
Summary: Make TransactionLogIterator related tests from db_test.cc to db_log_iter_test.cc

Test Plan:
db_test
db_log_iter_test

Reviewers: sdong, IslamAbdelRahman, igor, anthony

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42045
2015-07-14 16:08:21 -07:00
Yueh-Hsuan Chiang c3f98bb89b Move CompactionFilter tests in db_test.cc to db_compaction_filter_test.cc
Summary: Move CompactionFilter tests in db_test.cc to db_compaction_filter_test.cc

Test Plan:
db_test
db_compaction_filter_test

Reviewers: igor, sdong, IslamAbdelRahman, anthony

Reviewed By: anthony

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42207
2015-07-14 16:03:47 -07:00
agiardullo 18d5e1bf88 Remove db_impl_readonly dependency on utilities
Summary: Seems like the cleanest way to resolve this is to move CompactedDBImpl into db/.  CompactedDBImpl should probably live in the same place as DBImplReadonly since Opening the latter could end up instantiating the former.  Both DBImplReadonly and CompactedDBImpl inherit from DBImpl access protected members of DBImpl( and the latter access friendly private methods).

Test Plan: unit tests

Reviewers: sdong, yhchiang, kradhakrishnan, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42027
2015-07-14 11:32:54 -07:00
Islam AbdelRahman 49640bd82f Allow write_batch_test to run with ROCKSDB_LITE
Summary: Remove ColumnFamiliesBatchWithIndexTest from ROCKSDB_LITE since WriteBatchWithIndex is not supported

Test Plan: write_batch_test

Reviewers: yhchiang, sdong, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D42033
2015-07-14 10:35:35 -07:00
Igor Canadi a9c5109515 Deprecate purge_redundant_kvs_while_flush
Summary: This option is guarding the feature implemented 2 and a half years ago: D8991. The feature was enabled by default back then and has been running without issues. There is no reason why any client would turn this feature off. I found no reference in fbcode.

Test Plan: none

Reviewers: sdong, yhchiang, anthony, dhruba

Reviewed By: dhruba

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42063
2015-07-14 13:07:02 +02:00
Igor Canadi 5aea98ddd8 Deprecate WriteOptions::timeout_hint_us
Summary:
In one of our recent meetings, we discussed deprecating features that are not being actively used. One of those features, at least within Facebook, is timeout_hint. The feature is really nicely implemented, but if nobody needs it, we should remove it from our code-base (until we get a valid use-case). Some arguments:
* Less code == better icache hit rate, smaller builds, simpler code
* The motivation for adding timeout_hint_us was to work-around RocksDB's stall issue. However, we're currently addressing the stall issue itself (see @sdong's recent work on stall write_rate), so we should never see sharp lock-ups in the future.
* Nobody is using the feature within Facebook's code-base. Googling for `timeout_hint_us` also doesn't yield any users.

Test Plan: make check

Reviewers: anthony, kradhakrishnan, sdong, yhchiang

Reviewed By: yhchiang

Subscribers: sdong, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41937
2015-07-14 09:35:48 +02:00
Andres Notzli ae29495e4b Avoid manipulating const char* arrays
Summary:
We were manipulating `const char*` arrays in CompactionJob to
change the sequence number/types of keys. This patch changes
UpdateInternalKey() to use string methods to do the manipulation
and updates all calls accordingly.

Test Plan:
Added test case for UpdateInternalKey() in dbformat_test.
make && make check

Reviewers: sdong, rven, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41985
2015-07-14 00:21:41 -07:00
Andres Notzli ab137af4ba Partial cleanup of CompactionJob
Summary:
Logging, dealing with key prefix batches and updating stats
moved from CompactionJob::Run() into separate functions.

Test Plan: make all && make check

Reviewers: sdong, rven, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41919
2015-07-14 00:09:20 -07:00
Yueh-Hsuan Chiang b10cf4e2e0 Move DynamicLevel related db-tests to db_dynamic_level_test.cc
Summary: Move DynamicLevel related db-tests to db_dynamic_level_test.cc

Test Plan:
db_dynamic_level_test
db_test

Reviewers: igor, anthony, IslamAbdelRahman, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D42039
2015-07-13 19:00:30 -07:00
Islam AbdelRahman e290f5d3ce Block reduce_levels_test in ROCKSDB_LITE
Summary: Block reduce_levels_test in ROCKSDB_LITE as LDBCommand is not supported

Test Plan:
make reduce_levels_test -j64
OPT=-DROCKSDB_LITE make reduce_levels_test -j64
make check -j64

Reviewers: sdong, igor, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D41967
2015-07-13 18:45:55 -07:00
Yueh-Hsuan Chiang 49f42ad032 Move global static functions in db_test_util to DBTestBase
Summary:
Move global static functions in db_test_util to DBTestBase.
This is to prevent unused function warning when decoupling
db_test.cc into multiple files.

Test Plan: db_test

Reviewers: igor, sdong, anthony, IslamAbdelRahman, kradhakrishnan

Reviewed By: kradhakrishnan

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D42009
2015-07-13 17:41:41 -07:00
Yueh-Hsuan Chiang 625467a08a Move reusable part of db_test.cc to util/db_test_util.h
Summary:
Move reusable part of db_test.cc to util/db_test_util.h.
This makes it more possible to partition db_test.cc into
multiple smaller test files.

Also, fixed many old lint errors in db_test.

Test Plan: db_test

Reviewers: igor, anthony, IslamAbdelRahman, sdong, kradhakrishnan

Reviewed By: sdong, kradhakrishnan

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41973
2015-07-13 16:53:38 -07:00
Ari Ekmekji 8bca83e5dd Add tombstone information in CompactionJobStats
Summary:
Added new statistics in CompactionJobStats to keep track of
deletion entries and the expiration of those entries. Updated these
fields in compaction_job.cc as compaction took place and wrote a new
test in compaction_job_stats_test.cc to verify accuracy.

Test Plan:
Wrote new test DeletionStatsTest in
compaction_job_stats_test.cc to verify

Reviewers: sdong, igor, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D41355
2015-07-13 15:51:38 -07:00
sdong f9728640f3 "make format" against last 10 commits
Summary: This helps Windows port to format their changes, as discussed. Might have formatted some other codes too becasue last 10 commits include more.

Test Plan: Build it.

Reviewers: anthony, IslamAbdelRahman, kradhakrishnan, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D41961
2015-07-13 13:50:18 -07:00
sdong 76d3cd3286 Fix public API dependency on internal codes and dependency on MAX_INT32
Summary:
Public API depends on port/port.h which is wrong. Fix it.
Also with gcc 4.8.1 build was broken as MAX_INT32 was not recognized. Fix it by using ::max in linux.

Test Plan: Build it and try to build an external project on top of it.

Reviewers: anthony, yhchiang, kradhakrishnan, igor

Reviewed By: igor

Subscribers: yoshinorim, leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D41745
2015-07-11 10:32:11 -07:00
sdong 5fd11853cb Print Fast CRC32 support information in DB LOG
Summary: Print whether fast CRC32 is supported in DB info LOG

Test Plan: Run db_bench and see it prints out correctly.

Reviewers: yhchiang, anthony, kradhakrishnan, igor

Reviewed By: igor

Subscribers: MarkCallaghan, yoshinorim, leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D41733
2015-07-10 17:59:36 -07:00
Siying Dong e41cbd9c2f Merge pull request #646 from yuslepukhin/ms_win_port
Windows Port from Microsoft
2015-07-10 15:53:39 -07:00
sdong 041b6f95a2 perf_context: report time spent on reading index and bloom blocks
Summary: Add a perf context counter to help users figure out time spent on reading indexes and bloom filter blocks.

Test Plan: Will write a unit test

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D41433
2015-07-10 14:45:42 -07:00
Dmitri Smirnov c903ccc4c2 Merge from github/master 2015-07-09 18:01:08 -07:00
krad 7189e90c22 Fix a noisy unit test.
Summary: The t/DBTest.DropWrites test still fails under certain gcc version in release unit test.

I unfortunately cannot repro the failure (since the compilers have mapped library which I am not able to map to correctly). I am suspecting the clock skew.

Test Plan: Run make check

Reviewers:

CC: sdong igore

Task ID: #7312624

Blame Rev:
2015-07-09 13:43:52 -07:00
Aaron Feldman 1f4d565709 Add db_bench flag to set cache_index_and_filter_blocks
Summary:
The new flag --cache_index_and_filter_blocks sets
BlockBasedTableOptions.cache_index_and_filter_blocks

Test Plan: make db_bench. Working on benchmarks with the new flag.

Reviewers: igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D41481
2015-07-09 13:36:16 -07:00
Dmitri Smirnov d8586ab22b All of these are in the new code added past 3.10
1) Crash in env_win.cc that prevented db_test run to completion and some new tests
     2) Fix new corruption tests in DBTest by allowing a shared trunction of files. Note that this is generally needed ONLY for tests.
     3) Close database so WAL is closed prior to inducing corruption similar to what we did within Corruption tests.
2015-07-08 16:56:45 -07:00
Poornima Chozhiyath Raman 4bed00a44b Fix function name format according to google style
Summary: Change the naming style of getter and setters according to Google C++ style in compaction.h file

Test Plan: Compilation success

Reviewers: sdong

Reviewed By: sdong

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D41265
2015-07-08 15:21:10 -07:00
krad e2e3d84b2c Added multi WAL log testing to recovery tests.
Summary: Currently there is no test in the suite to test the case where
there are multiple WAL files and there is a corruption in one of them. We have
tests for single WAL file corruption scenarios. Added tests to mock
the scenarios for all combinations of recovery modes and corruption in
specified file locations.

Test Plan: Run make check

Reviewers: sdong igor

CC: leveldb@

Task ID: #7501229

Blame Rev:
2015-07-08 14:39:00 -07:00
Dmitri Smirnov ef4b87f1b2 Commit both PR and internal code review changes 2015-07-07 16:58:20 -07:00
agiardullo 4f56632b16 Fix occasional failure in compaction_job_test
Summary: Coverage test has been occasionally failing due to this timing check.

Test Plan: run test

Reviewers: yhchiang

Reviewed By: yhchiang

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41367
2015-07-07 16:10:23 -07:00
Poornima Chozhiyath Raman 411c8e3d19 Build fail fix
Summary: Build fail fix. Type cast issues.

Test Plan: compiled

Reviewers: sdong, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D41349
2015-07-07 15:21:17 -07:00
Poornima Chozhiyath Raman c0b23dd5b0 Enabling trivial move in universal compaction
Summary: This change enables trivial move if all the input files are non onverlapping while doing Universal Compaction.

Test Plan: ./compaction_picker_test and db_test ran successfully with the new testcases.

Reviewers: sdong

Reviewed By: sdong

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D40875
2015-07-07 14:18:55 -07:00
Yueh-Hsuan Chiang d8e3e766f9 Fixed a bug in test ThreadStatusSingleCompaction
Summary:
Fixed a bug in test ThreadStatusSingleCompaction where
SyncPoint traces are not cleared before the test begins
its second iteration.

Test Plan: db_test

Reviewers: sdong, anthony, IslamAbdelRahman, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41337
2015-07-07 14:00:03 -07:00
Yueh-Hsuan Chiang 4ce5be4255 fixed leaking log::Writers
Summary: Fixes valgrind errors in column_family_test.

Test Plan: `make check`, `make valgrind_check`

Reviewers: igor, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D41181
2015-07-07 12:10:10 -07:00
Yueh-Hsuan Chiang 685582a0b4 Revert two diffs related to DBIter::FindPrevUserKey()
Summary:
This diff reverts the following two previous diffs related to
DBIter::FindPrevUserKey(), which makes db_stress unstable.
We should bake a better fix for this.

* "Fix a comparison in DBIter::FindPrevUserKey()"
  ec70fea4c4.

* "Fixed endless loop in DBIter::FindPrevUserKey()"
  acee2b08a2.

Test Plan: db_stress

Reviewers: anthony, igor, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41301
2015-07-07 11:36:24 -07:00
Andres Notzli 58d7ab3c68 Added tests for ExpandWhileOverlapping()
Summary:
This patch adds three test cases for ExpandWhileOverlapping()
to the compaction_picker_test test suite.
ExpandWhileOverlapping() only has an effect if the comparison
function for the internal keys allows for overlapping user
keys in different SST files on the same level. Thus, this
patch adds a comparator based on sequence numbers to
compaction_picker_test for the new test cases.

Test Plan:
- make compaction_picker_test && ./compaction_picker_test
  -> All tests pass
- Replace body of ExpandWhileOverlapping() with `return true`
  -> Compile and run ./compaction_picker_test as before
  -> New tests fail

Reviewers: sdong, yhchiang, rven, anthony, IslamAbdelRahman, kradhakrishnan, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41277
2015-07-06 22:25:27 -07:00
Igor Canadi 155ce60daf Fix compaction_job_test
Summary:
Two issues:
* the input keys to the compaction don't include sequence number.
* sequence number is set to max(seq_num), but it should be set to max(seq_num)+1, because the condition here is strictly-larger (i.e. we will only zero-out sequence number if the DB's sequence number is strictly greater than the key's sequence number): https://github.com/facebook/rocksdb/blob/master/db/compaction_job.cc#L830

Test Plan: make compaction_job_test && ./compaction_job_test

Reviewers: sdong, lovro

Reviewed By: lovro

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D41247
2015-07-06 11:14:08 -07:00
Dmitri Smirnov d2f0912bd3 Merge the latest changes from github/master 2015-07-02 17:23:41 -07:00
Mike Kolupaev 218487d8dc [wal changes 1/3] fixed unbounded wal growth in some workloads
Summary:
This fixes the following scenario we've hit:
 - we reached max_total_wal_size, created a new wal and scheduled flushing all memtables corresponding to the old one,
 - before the last of these flushes started its column family was dropped; the last background flush call was a no-op; no one removed the old wal from alive_logs_,
 - hours have passed and no flushes happened even though lots of data was written; data is written to different column families, compactions are disabled; old column families are dropped before memtable grows big enough to trigger a flush; the old wal still sits in alive_logs_ preventing max_total_wal_size limit from kicking in,
 - a few more hours pass and we run out disk space because of one huge .log file.

Test Plan: `make check`; backported the new test, checked that it fails without this diff

Reviewers: igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D40893
2015-07-02 14:27:00 -07:00
Dmitri Smirnov 9dbde7277c Merge remote-tracking branch 'origin' into ms_win_port 2015-07-02 11:34:22 -07:00
Dmitri Smirnov 18285c1e2f Windows Port from Microsoft
Summary: Make RocksDb build and run on Windows to be functionally
 complete and performant. All existing test cases run with no
 regressions. Performance numbers are in the pull-request.

 Test plan: make all of the existing unit tests pass, obtain perf numbers.

 Co-authored-by: Praveen Rao praveensinghrao@outlook.com
 Co-authored-by: Sherlock Huang baihan.huang@gmail.com
 Co-authored-by: Alex Zinoviev alexander.zinoviev@me.com
 Co-authored-by: Dmitri Smirnov dmitrism@microsoft.com
2015-07-01 16:13:56 -07:00
sdong 05e2831966 Allocate LevelFileIteratorState and LevelFileNumIterator from DB iterator's arena
Summary: Try to allocate LevelFileIteratorState and LevelFileNumIterator from DB iterator's arena, instead of calling malloc and free.

Test Plan: valgrind check

Reviewers: rven, yhchiang, anthony, kradhakrishnan, igor

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D40929
2015-06-30 17:30:38 -07:00