Commit graph

636 commits

Author SHA1 Message Date
Tyler Harter c2bd8f4824 Prefix scan: db_bench and bug fixes
Summary: If use_prefix_filters is set and read_range>1, then the random seeks will set a the prefix filter to be the prefix of the key which was randomly selected as the target.  Still need to add statistics (perhaps in a separate diff).

Test Plan: ./db_bench --benchmarks=fillseq,prefixscanrandom --num=10000000 --statistics=1 --use_prefix_blooms=1 --use_prefix_api=1 --bloom_bits=10

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb, haobo

Differential Revision: https://reviews.facebook.net/D12273
2013-08-22 16:06:50 -07:00
Simha Venkataramaiah 60bf2b7d4a Add APIs to query SST file metadata and to delete specific SST files
Summary: An api to query the level, key ranges, size etc for each SST file and an api to delete a specific file from the db and all associated state in the bookkeeping datastructures.

Notes: Editing the manifest version does not release the obsolete files right away. However deleting the file directly will mess up the iterator. We may need a more aggressive/timely file deletion api.

I have used std::unique_ptr - will switch to boost:: since this is external. thoughts?

Unit test is fragile right now as it expects the compaction at certain levels.

Test Plan: unittest

Reviewers: dhruba, vamsi, emayanke

CC: zshao, leveldb, haobo

Task ID: #

Blame Rev:
2013-08-22 15:27:19 -07:00
Jim Paton bc8eed12d9 Do not use relative paths in build system
Summary: Previously, RocksDB's build scripts used relative pathnames like ./build_detect_platform. This can cause problems if the user uses CDPATH. Also, it just doesn't seem right to me.

Test Plan:
make clean
make -j32 check

Reviewers: MarkCallaghan, dhruba, kailiu

Reviewed By: kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12459
2013-08-22 14:53:51 -07:00
Jim Paton cb703c9d03 Allow WriteBatch::Handler to abort iteration
Summary:
Sometimes you don't need to iterate through the whole WriteBatch. This diff makes the Handler member functions return a bool that indicates whether to abort or not. If they return true, the iteration stops.

One thing I just thought of is that this will break backwards-compability. Maybe it would be better to add a virtual member function WriteBatch::Handler::ShouldAbort() that returns false by default. Comments requested.

I still have to add a new unit test for the abort code, but let's finalize the API first.

Test Plan: make -j32 check

Reviewers: dhruba, haobo, vamsi, emayanke

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12339
2013-08-21 18:27:48 -07:00
Haobo Xu f9e2decf7c [RocksDB] Minor iterator cleanup
Summary: Was going through the iterator related code, did some cleanup along the way. Basically replaced array with vector and adopted range based loop where applicable.

Test Plan: make check; make valgrind_check

Reviewers: dhruba, emayanke

Reviewed By: emayanke

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12435
2013-08-21 16:54:48 -07:00
Mayank Agarwal 404d63ac3e Add TODO for DBToStackableDB function which doesn't work yet
Summary:

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:
2013-08-20 21:33:53 -07:00
Xing Jin af732c7ba8 Add universal compaction to db_stress nightly build
Summary:
Most code change in this diff is code cleanup/rewrite. The logic changes include:

(1) add universal compaction to db_crashtest2.py
(2) randomly set --test_batches_snapshots to be 0 or 1 in db_crashtest2.py. Old codes always use 1.
(3) use different tmp directory as db directory in different runs. I saw some intermittent errors in my local tests. Use of different tmp directory seems to be able to solve the issue.

Test Plan: Have run "make crashtest" for multiple times. Also run "make all check"

Reviewers: emayanke, dhruba, haobo

Reviewed By: emayanke

Differential Revision: https://reviews.facebook.net/D12369
2013-08-20 17:37:49 -07:00
Deon Nicholas b87dcae1a3 Made merge_oprator a shared_ptr; and added TTL unit tests
Test Plan:
- make all check;
- make release;
- make stringappend_test; ./stringappend_test

Reviewers: haobo, emayanke

Reviewed By: haobo

CC: leveldb, kailiu

Differential Revision: https://reviews.facebook.net/D12381
2013-08-20 13:35:28 -07:00
Mayank Agarwal 3ab2792f93 Add default info to comment in leveldb/options.h for no_block_cache
Summary: to ley clients know

Test Plan: visual
2013-08-19 14:29:40 -07:00
Mayank Agarwal 28e6fe5e9f Correct documentation for no_block_cache in leveldb/options.h
Summary: false shoudl have been true in comment

Test Plan: visual
2013-08-19 14:27:19 -07:00
Mayank Agarwal 8a3547d38e API for getting archived log files
Summary: Also expanded class LogFile to have startSequene and FileSize and exposed it publicly

Test Plan: make all check

Reviewers: dhruba, haobo

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12087
2013-08-19 13:37:04 -07:00
Deon Nicholas e1346968d8 Merge operator fixes part 1.
Summary:
-Added null checks and revisions to DBIter::MergeValuesNewToOld()
-Added DBIter test to stringappend_test
-Major fix with Merge and TTL
More plans for fixes later.

Test Plan:
-make clean; make stringappend_test -j 32; ./stringappend_test
-make all check;

Reviewers: haobo, emayanke, vamsi, dhruba

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12315
2013-08-19 11:42:47 -07:00
Kai Liu 1635ea06c2 Remove PLATFORM_SHARED_CFLAGS when compiling .o files
Summary:

The flags is accidentally introduced, and resulted in problems in 3rd party release.

Test Plan:

run make in all platforms (when doing the 3rd party release)
2013-08-16 16:39:23 -07:00
Kai Liu fd2f47dbe5 Improve the build files to simplify the 3rd party release process
Summary:
* Added LIBNAME to enable configurable library name.
* remove/check fPIC in linux platform from build_detect_platform

Test Plan: make

Reviewers: emayanke

Differential Revision: https://reviews.facebook.net/D12321
2013-08-16 12:05:27 -07:00
Mayank Agarwal 387ac0f1e1 Expose statistic for sequence number and implement setTickerCount
Summary: statistic for sequence number is needed by wormhole. setTickerCount is demanded for this statistic. I can't simply recordTick(max_sequence) when db recovers because the statistic iobject is owned by client and may/may not be reset during reopen. Eg. statistic is reset in mcrocksdb whereas it is not in db_stress. Therefore it is best to go with setTickerCount

Test Plan: ./db_stress ... --statistics=1 and observed expected sequence number

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12327
2013-08-15 23:00:20 -07:00
Deon Nicholas d1d3d15eb7 Tiny fix to db_bench for make release.
Summary:
In release, "found variable assigned but not used anywhere". Changed it to work with
assert. Someone accept this :).

Test Plan: make release -j 32

Reviewers: haobo, dhruba, emayanke

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12309
2013-08-15 17:50:12 -07:00
Deon Nicholas ad48c3c262 Benchmarking for Merge Operator
Summary:
Updated db_bench and utilities/merge_operators.h to allow for dynamic benchmarking
of merge operators in db_bench. Added a new test (--benchmarks=mergerandom), which performs
a bunch of random Merge() operations over random keys. Also added a "--merge_operator=" flag
so that the tester can easily benchmark different merge operators. Currently supports
the PutOperator and UInt64Add operator. Support for stringappend or list append may come later.

Test Plan:
	1. make db_bench
	2. Test the PutOperator (simulating Put) as follows:
./db_bench --benchmarks=fillrandom,readrandom,updaterandom,readrandom,mergerandom,readrandom --merge_operator=put
--threads=2

3. Test the UInt64AddOperator (simulating numeric addition) similarly:
./db_bench --value_size=8 --benchmarks=fillrandom,readrandom,updaterandom,readrandom,mergerandom,readrandom
--merge_operator=uint64add --threads=2

Reviewers: haobo, dhruba, zshao, MarkCallaghan

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11535
2013-08-15 17:13:07 -07:00
Kai Liu f3dea8c13c Commit the correct fix for Jenkin failure
Summary:

My last commit is not the correct one. Fix it in this diff.

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:
2013-08-15 14:57:44 -07:00
Kai Liu 159c19ac7b Fix Jenkin build failure
Summary:

Previously I changed the line `source ./fbcode.gcc471.sh` to `source fbcode.gcc471.sh`. It works in my devbox but failed in some jenkin servers. I revert the previous code to make sure it works well under all circumstances.

Test Plan:

Test in the jenkin server as well as dev box.

Reviewers:

CC:

Task ID: #

Blame Rev:
2013-08-15 14:49:31 -07:00
Kai Liu 457dcc605a Clean up the Makefile and the build scripts
Summary: As Aaron suggested, there are quite some problems with our Makefile and scripts. So in this diff I did some cleanup for them and revise some part of the scripts/makefile to help people better understand some mysterious parts.

Test Plan:
Ran make in several modes;
Ran the updated scripts.

Reviewers: dhruba, emayanke, akushner

Differential Revision: https://reviews.facebook.net/D12285
2013-08-15 12:59:45 -07:00
Tyler Harter 85d83a150b Update crashtests to match D12267
Summary: I changed the db_stress configs, but forgot to update the scripts using the old configs.

Test Plan: 'make blackbox_crash_test' and 'make whitebox_crash_test' start running normally now (I haven't run them til the end, though).

Reviewers: vamsi

Reviewed By: vamsi

CC: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D12303
2013-08-15 10:14:32 -07:00
Xing Jin 0a5afd1afc Minor fix to current codes
Summary:
Minor fix to current codes, including: coding style, output format,
comments. No major logic change. There are only 2 real changes, please see my inline comments.

Test Plan: make all check

Reviewers: haobo, dhruba, emayanke

Differential Revision: https://reviews.facebook.net/D12297
2013-08-14 23:03:57 -07:00
Tyler Harter 7612d496ff Add prefix scans to db_stress (and bug fix in prefix scan)
Summary: Added support for prefix scans.

Test Plan: ./db_stress --max_key=4096 --ops_per_thread=10000

Reviewers: dhruba, vamsi

Reviewed By: vamsi

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12267
2013-08-14 16:58:36 -07:00
Jim Paton 0307c5fe3a Implement log blobs
Summary:
This patch adds the ability for the user to add sequences of arbitrary data (blobs) to write batches. These blobs are saved to the log along with everything else in the write batch. You can add multiple blobs per WriteBatch and the ordering of blobs, puts, merges, and deletes are preserved.

Blobs are not saves to SST files. RocksDB ignores blobs in every way except for writing them to the log.

Before committing this patch, I need to add some test code. But I'm submitting it now so people can comment on the API.

Test Plan: make -j32 check

Reviewers: dhruba, haobo, vamsi

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12195
2013-08-14 16:32:46 -07:00
Haobo Xu d9dd2a1926 [RocksDB] Expose thread local perf counter for low overhead, per call level performance statistics.
Summary:
As title. No locking/atomic is needed due to thread local. There is also no need to modify the existing client interface, in order to expose related counters.

perf_context_test shows a simple example of retrieving the number of user key comparison done for each put and get call. More counters could be added later.

Sample output
./perf_context_test 1000000
==== Test PerfContextTest.KeyComparisonCount
Inserting 1000000 key/value pairs
...
total user key comparison get: 43446523
total user key comparison put: 8017877
max user key comparison get: 88939
avg user key comparison get:43

Basically, the current skiplist does well on average, but could perform poorly in extreme cases.

Test Plan: run perf_context_test <total number of entries to put/get>

Reviewers: dhruba

Differential Revision: https://reviews.facebook.net/D12225
2013-08-14 15:24:06 -07:00
Tyler Harter a8f47a4006 Add options to dump.
Summary: added options to Dump() I missed in D12027.  I also ran a script to look for other missing options and found a couple which I added.  Should we also print anything for "PrepareForBulkLoad", "memtable_factory", and "statistics"?  Or should we leave those alone since it's not easy to print useful info for those?

Test Plan: run anything and look at LOG file to make sure these are printed now.

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12219
2013-08-14 09:06:10 -07:00
Mayank Agarwal f1bf169484 Counter for merge failure
Summary:
With Merge returning bool, it can keep failing silently(eg. While faling to fetch timestamp in TTL). We need to detect this through a rocksdb counter which can get bumped whenever Merge returns false. This will also be super-useful for the mcrocksdb-counter service where Merge may fail.
Added a counter NUMBER_MERGE_FAILURES and appropriately updated db/merge_helper.cc

I felt that it would be better to directly add counter-bumping in Merge as a default function of MergeOperator class but user should not be aware of this, so this approach seems better to me.

Test Plan: make all check

Reviewers: dnicholas, haobo, dhruba, vamsi

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12129
2013-08-13 14:25:42 -07:00
Tyler Harter f5f1842282 Prefix filters for scans (v4)
Summary: Similar to v2 (db and table code understands prefixes), but use ReadOptions as in v3.  Also, make the CreateFilter code faster and cleaner.

Test Plan: make db_test; export LEVELDB_TESTS=PrefixScan; ./db_test

Reviewers: dhruba

Reviewed By: dhruba

CC: haobo, emayanke

Differential Revision: https://reviews.facebook.net/D12027
2013-08-13 14:04:56 -07:00
sumeet 3b81df34bd Separate compaction filter for each compaction
Summary:
If we have same compaction filter for each compaction,
application cannot know about the different compaction processes.
Later on, we can put in more details in compaction filter for the
application to consume and use it according to its needs. For e.g. In
the universal compaction, we have a compaction process involving all the
files while others don't involve all the files. Applications may want to
collect some stats only when during full compaction.

Test Plan: run existing unit tests

Reviewers: haobo, dhruba

Reviewed By: dhruba

CC: xinyaohu, leveldb

Differential Revision: https://reviews.facebook.net/D12057
2013-08-13 10:56:20 -07:00
Kai Liu 9f6b8f0032 Add automatic coverage report scripts
Summary:
Ultimate goals of the coverage report are:

* Report the coverage for all files (done in this diff)
* Report the coverage for recently updated files (not fully finished)
* Report is available in html form (done in this diff, but need some extra work to integrate it in Jenkin)

Task link: https://our.intern.facebook.com/intern/tasks/?s=1154818042&t=2604914

Test Plan:
Ran: coverage/coverage_test.sh

The sample output can be found here: https://phabricator.fb.com/P2433892

Reviewers: dhruba, emayanke

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11943
2013-08-12 23:53:37 -07:00
Dhruba Borthakur 03bd4461ad Merge branch 'performance' of github.com:facebook/rocksdb into performance 2013-08-12 10:31:21 -07:00
Dhruba Borthakur f3967a5132 Merge remote-tracking branch 'origin' into performance 2013-08-12 09:58:50 -07:00
Dhruba Borthakur 93d77a27d2 Universal Compaction should keep DeleteMarkers unless it is the earliest file.
Summary:
The pre-existing code was purging a DeleteMarker if thay key did not
exist in deeper levels.  But in the Universal Compaction Style, all
files are in Level0. For compaction runs that did not include the
earliest file, we were erroneously purging the DeleteMarkers.

The fix is to purge DeleteMarkers only if the compaction includes
the earlist file.

Test Plan: DBTest.Randomized triggers this code path.

Differential Revision: https://reviews.facebook.net/D12081
2013-08-09 14:03:57 -07:00
Xing Jin 8ae905ed63 Fix unit tests for universal compaction (step 2)
Summary:
Continue fixing existing unit tests for universal compaction. I have
tried to apply universal compaction to all unit tests those haven't
called ChangeOptions(). I left a few which are either apparently not
applicable to universal compaction (because they check files/keys/values
at level 1 or above levels), or apparently not related to compaction
(e.g., open a file, open a db).

I also add a new unit test for universal compaction.

Good news is I didn't see any bugs during this round.

Test Plan: Ran "make all check" yesterday. Has rebased and is rerunning

Reviewers: haobo, dhruba

Differential Revision: https://reviews.facebook.net/D12135
2013-08-09 13:35:44 -07:00
Haobo Xu 3a3b1c3e6c [RocksDB] Improve manifest dump to print internal keys in hex for version edits.
Summary: Currently, VersionEdit::DebugString always display internal keys in the original ascii format. This could cause manifest dump to be truncated if internal keys contain special charactors (like null). Also added an option --input_key_hex for ldb idump to indicate that the passed in user keys are in hex.

Test Plan: run ldb manifest_dump

Reviewers: dhruba, emayanke

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12111
2013-08-08 16:19:01 -07:00
Haobo Xu 58a0ae06dc [RocksDB] Improve sst_dump to take user key range
Summary: The ability to dump internal keys associated with certain user keys, directly from sst files, is very useful for diagnosis. Will incorporate it directly into ldb later.

Test Plan: run it

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12075
2013-08-08 15:31:12 -07:00
Xing Jin 17b8f786a3 Fix unit tests/bugs for universal compaction (first step)
Summary:
This is the first step to fix unit tests and bugs for universal
compactiion. I added universal compaction option to ChangeOptions(), and
fixed all unit tests calling ChangeOptions(). Some of these tests
obviously assume more than 1 level and check file number/values in level
1 or above levels. I set kSkipUniversalCompaction for these tests.

The major bug I found is manual compaction with universal compaction never stops. I have put a fix for
it.

I have also set universal compaction as the default compaction and found
at least 20+ unit tests failing. I haven't looked into the details. The
next step is to check all unit tests without calling ChangeOptions().

Test Plan: make all check

Reviewers: dhruba, haobo

Differential Revision: https://reviews.facebook.net/D12051
2013-08-07 14:05:44 -07:00
Dhruba Borthakur f5fa26b6a9 Merge branch 'performance' of github.com:facebook/rocksdb into performance
Conflicts:
	db/builder.cc
	db/db_impl.cc
	db/version_set.cc
	include/leveldb/statistics.h
2013-08-07 11:58:06 -07:00
Mayank Agarwal 678d3a1633 Updating readme to 2.1
Summary:

Test Plan:

Reviewers:

CC:

Task ID: #

Blame Rev:
2013-08-06 14:43:16 -07:00
Deon Nicholas 68a4cdf3f7 Build fix with merge_test and ttl 2013-08-06 11:42:21 -07:00
Deon Nicholas e37eb21e92 minor change to fix build 2013-08-06 11:02:19 -07:00
Deon Nicholas c2d7826ced [RocksDB] [MergeOperator] The new Merge Interface! Uses merge sequences.
Summary:
Here are the major changes to the Merge Interface. It has been expanded
to handle cases where the MergeOperator is not associative. It does so by stacking
up merge operations while scanning through the key history (i.e.: during Get() or
Compaction), until a valid Put/Delete/end-of-history is encountered; it then
applies all of the merge operations in the correct sequence starting with the
base/sentinel value.

I have also introduced an "AssociativeMerge" function which allows the user to
take advantage of associative merge operations (such as in the case of counters).
The implementation will always attempt to merge the operations/operands themselves
together when they are encountered, and will resort to the "stacking" method if
and only if the "associative-merge" fails.

This implementation is conjectured to allow MergeOperator to handle the general
case, while still providing the user with the ability to take advantage of certain
efficiencies in their own merge-operator / data-structure.

NOTE: This is a preliminary diff. This must still go through a lot of review,
revision, and testing. Feedback welcome!

Test Plan:
  -This is a preliminary diff. I have only just begun testing/debugging it.
  -I will be testing this with the existing MergeOperator use-cases and unit-tests
(counters, string-append, and redis-lists)
  -I will be "desk-checking" and walking through the code with the help gdb.
  -I will find a way of stress-testing the new interface / implementation using
db_bench, db_test, merge_test, and/or db_stress.
  -I will ensure that my tests cover all cases: Get-Memtable,
Get-Immutable-Memtable, Get-from-Disk, Iterator-Range-Scan, Flush-Memtable-to-L0,
Compaction-L0-L1, Compaction-Ln-L(n+1), Put/Delete found, Put/Delete not-found,
end-of-history, end-of-file, etc.
  -A lot of feedback from the reviewers.

Reviewers: haobo, dhruba, zshao, emayanke

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11499
2013-08-05 20:14:32 -07:00
Mayank Agarwal 73f9518b21 Fix build
Summary: remove reference

Test Plan: make OPT=-g

Reviewers:

CC:

Task ID: #

Blame Rev:
2013-08-05 19:22:12 -07:00
Jim Paton 8e792e5896 Add soft_rate_limit stats
Summary: This diff adds histogram stats for soft_rate_limit stalls. It also renames the old rate_limit stats to hard_rate_limit.

Test Plan: make -j32 check

Reviewers: dhruba, haobo, MarkCallaghan

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12021
2013-08-05 18:45:23 -07:00
Mayank Agarwal 1d7b4765c3 Expose base db object from ttl wrapper
Summary: rocksdb replicaiton will need this when writing value+TS from master to slave 'as is'

Test Plan: make

Reviewers: dhruba, vamsi, haobo

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11919
2013-08-05 18:44:14 -07:00
Jim Paton 1036537c94 Add soft and hard rate limit support
Summary:
This diff adds support for both soft and hard rate limiting. The following changes are included:

1) Options.rate_limit is renamed to Options.hard_rate_limit.
2) Options.rate_limit_delay_milliseconds is renamed to Options.rate_limit_delay_max_milliseconds.
3) Options.soft_rate_limit is added.
4) If the maximum compaction score is > hard_rate_limit and rate_limit_delay_max_milliseconds == 0, then writes are delayed by 1 ms at a time until the max compaction score falls below hard_rate_limit.
5) If the max compaction score is > soft_rate_limit but <= hard_rate_limit, then writes are delayed by 0-1 ms depending on how close we are to hard_rate_limit.
6) Users can disable 4 by setting hard_rate_limit = 0. They can add a limit to the maximum amount of time waited by setting rate_limit_delay_max_milliseconds > 0. Thus, the old behavior can be preserved by setting soft_rate_limit = 0, which is the default.

Test Plan:
make -j32 check
./db_stress

Reviewers: dhruba, haobo, MarkCallaghan

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12003
2013-08-05 15:43:49 -07:00
Mayank Agarwal cacd812fb2 Support user's compaction filter in TTL logic
Summary: TTL uses compaction filter to purge key-values and required the user to not pass one. This diff makes it accommodating of user's compaciton filter. Added test to ttl_test

Test Plan: make; ./ttl_test

Reviewers: dhruba, haobo, vamsi

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11973
2013-08-05 11:28:01 -07:00
Mayank Agarwal 7c9093ab53 Changing Makefile to have rocksdb instead of leveldb in binary-names
Summary: did a find-replace

Test Plan: make

Reviewers: dhruba, haobo

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11979
2013-08-05 11:14:01 -07:00
Dhruba Borthakur 711a30cb30 Merge branch 'master' into performance
Conflicts:
	include/leveldb/options.h
	include/leveldb/statistics.h
	util/options.cc
2013-08-02 10:22:08 -07:00
Mayank Agarwal c42485f67c Merge operator for ttl
Summary: Implemented a TtlMergeOperator class which inherits from MergeOperator and is TTL aware. It strips out timestamp from existing_value and attaches timestamp to new_value, calling user-provided-Merge in between.

Test Plan: make all check

Reviewers: haobo, dhruba

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11775
2013-08-01 09:27:17 -07:00