Summary:
This branch extends existing property map which keeps values in doubles to keep values in strings so that it can be used to provide wider range of properties. The immediate need for that is to provide IO stall stats in an easy parseable way to MyRocks which is also part of this branch.
Closes https://github.com/facebook/rocksdb/pull/2794
Differential Revision: D5717676
Pulled By: Tema
fbshipit-source-id: e34ba5b79ba774697f7b97ce1138d8fd55471b8a
Summary:
Allow user to reduce number of levels in LSM by issue a full CompactRange() and put the result in a lower level, and then reopen DB with reduced options.num_levels. Previous this will fail on reopen on when recovery replaying the previous MANIFEST and found a historical file was on a higher level than the new options.num_levels. The workaround was after CompactRange(), reopen the DB with old num_levels, which will create a new MANIFEST, and then reopen the DB again with new num_levels.
This patch relax the check of levels during recovery. It allows DB to open if there was a historical file on level > options.num_levels, but was also deleted.
Closes https://github.com/facebook/rocksdb/pull/2740
Differential Revision: D5629354
Pulled By: yiwu-arbug
fbshipit-source-id: 545903f6b36b6083e8cbaf777176aef2f488021d
Summary:
Right now, if direct I/O is enabled, prefetching the last 512KB cannot be applied, except compaction inputs or readahead is enabled for iterators. This can create a lot of I/O for HDD cases. To solve the problem, the 512KB is prefetched in block based table if direct I/O is enabled. The prefetched buffer is passed in totegher with random access file reader, so that we try to read from the buffer before reading from the file. This can be extended in the future to support flexible user iterator readahead too.
Closes https://github.com/facebook/rocksdb/pull/2708
Differential Revision: D5593091
Pulled By: siying
fbshipit-source-id: ee36ff6d8af11c312a2622272b21957a7b5c81e7
Summary:
This reverts the previous commit 1d7048c598, which broke the build.
Did a `git revert 1d7048c`.
Closes https://github.com/facebook/rocksdb/pull/2627
Differential Revision: D5476473
Pulled By: sagar0
fbshipit-source-id: 4756ff5c0dfc88c17eceb00e02c36176de728d06
Summary: This uses `clang-tidy` to comment out unused parameters (in functions, methods and lambdas) in fbcode. Cases that the tool failed to handle are fixed manually.
Reviewed By: igorsugak
Differential Revision: D5454343
fbshipit-source-id: 5dee339b4334e25e963891b519a5aa81fbf627b2
Summary:
This PR adds support for encrypting data stored by RocksDB when written to disk.
It adds an `EncryptedEnv` override of the `Env` class with matching overrides for sequential&random access files.
The encryption itself is done through a configurable `EncryptionProvider`. This class creates is asked to create `BlockAccessCipherStream` for a file. This is where the actual encryption/decryption is being done.
Currently there is a Counter mode implementation of `BlockAccessCipherStream` with a `ROT13` block cipher (NOTE the `ROT13` is for demo purposes only!!).
The Counter operation mode uses an initial counter & random initialization vector (IV).
Both are created randomly for each file and stored in a 4K (default size) block that is prefixed to that file. The `EncryptedEnv` implementation is such that clients of the `Env` class do not see this prefix (nor data, nor in filesize).
The largest part of the prefix block is also encrypted, and there is room left for implementation specific settings/values/keys in there.
To test the encryption, the `DBTestBase` class has been extended to consider a new environment variable called `ENCRYPTED_ENV`. If set, the test will setup a encrypted instance of the `Env` class to use for all tests.
Typically you would run it like this:
```
ENCRYPTED_ENV=1 make check_some
```
There is also an added test that checks that some data inserted into the database is or is not "visible" on disk. With `ENCRYPTED_ENV` active it must not find plain text strings, with `ENCRYPTED_ENV` unset, it must find the plain text strings.
Closes https://github.com/facebook/rocksdb/pull/2424
Differential Revision: D5322178
Pulled By: sdwilsh
fbshipit-source-id: 253b0a9c2c498cc98f580df7f2623cbf7678a27f
Summary:
Allow users to rate limit background work based on read bytes, written bytes, or sum of read and written bytes. Support these by changing the RateLimiter API, so no additional options were needed.
Closes https://github.com/facebook/rocksdb/pull/2433
Differential Revision: D5216946
Pulled By: ajkr
fbshipit-source-id: aec57a8357dbb4bfde2003261094d786d94f724e
Summary:
If ReadOptions.low_pri=true and compaction is behind, the write will either return immediate or be slowed down based on ReadOptions.no_slowdown.
Closes https://github.com/facebook/rocksdb/pull/2369
Differential Revision: D5127619
Pulled By: siying
fbshipit-source-id: d30e1cff515890af0eff32dfb869d2e4c9545eb0
Summary:
Improve write buffer manager in several ways:
1. Size is tracked when arena block is allocated, rather than every allocation, so that it can better track actual memory usage and the tracking overhead is slightly lower.
2. We start to trigger memtable flush when 7/8 of the memory cap hits, instead of 100%, and make 100% much harder to hit.
3. Allow a cache object to be passed into buffer manager and the size allocated by memtable can be costed there. This can help users have one single memory cap across block cache and memtable.
Closes https://github.com/facebook/rocksdb/pull/2350
Differential Revision: D5110648
Pulled By: siying
fbshipit-source-id: b4238113094bf22574001e446b5d88523ba00017
Summary:
- `max_background_flushes` and `max_background_compactions` are still supported for backwards compatibility
- `base_background_compactions` is completely deprecated. Now we just throttle to one background compaction when there's no pressure.
- `max_background_jobs` is added to automatically partition the concurrent background jobs into flushes vs compactions. Currently it's very simple as we just allocate one-fourth of the jobs to flushes, and the remaining can be used for compactions.
- The test cases that set `base_background_compactions > 1` needed to be updated. I just grab the pressure token such that the desired number of compactions can be scheduled.
Closes https://github.com/facebook/rocksdb/pull/2205
Differential Revision: D4937461
Pulled By: ajkr
fbshipit-source-id: df52cbbd497e13bbc9a60560a5ac2a2526b3f1f9
Summary:
fix test failure of ReadAmpBitmap and ReadAmpBitmapLiveInCacheAfterDBClose.
test ReadAmpBitmapLiveInCacheAfterDBClose individually and make check
Closes https://github.com/facebook/rocksdb/pull/2271
Differential Revision: D5038133
Pulled By: lightmark
fbshipit-source-id: 803cd6f45ccfdd14a9d9473c8af311033e164be8
Summary:
- added a feature test in build_detect_platform to check whether sched_getcpu() is available. glibc offers it only on some platforms (e.g., linux but not mac); this way should be easier than maintaining a list of platforms on which it's available.
- refactored PhysicalCoreID() to be simpler / less repetitive. ordered the conditional compilation clauses from most-to-least preferred
Closes https://github.com/facebook/rocksdb/pull/2272
Differential Revision: D5038093
Pulled By: ajkr
fbshipit-source-id: 81d7db3cc620250de220bdeb3194b2b3d7673de7
Summary:
Consider BlockReadAmpBitmap with bytes_per_bit = 32. Suppose bytes [a, b) were used, while bytes [a-32, a)
and [b+1, b+33) weren't used; more formally, the union of ranges passed to BlockReadAmpBitmap::Mark() contains [a, b) and doesn't intersect with [a-32, a) and [b+1, b+33). Then bits [floor(a/32), ceil(b/32)] will be set, and so the number of useful bytes will be estimated as (ceil(b/32) - floor(a/32)) * 32, which is on average equal to b-a+31.
An extreme example: if we use 1 byte from each block, it'll be counted as 32 bytes from each block.
It's easy to remove this bias by slightly changing the semantics of the bitmap. Currently each bit represents a byte range [i*32, (i+1)*32).
This diff makes each bit represent a single byte: i*32 + X, where X is a random number in [0, 31] generated when bitmap is created. So, e.g., if you read a single byte at random, with probability 31/32 it won't be counted at all, and with probability 1/32 it will be counted as 32 bytes; so, on average it's counted as 1 byte.
*But there is one exception: the last bit will always set with the old way.*
(*) - assuming read_amp_bytes_per_bit = 32.
Closes https://github.com/facebook/rocksdb/pull/2259
Differential Revision: D5035652
Pulled By: lightmark
fbshipit-source-id: bd98b1b9b49fbe61f9e3781d07f624e3cbd92356
Summary:
Replacement of #2147
The change was squashed due to a lot of conflicts.
Closes https://github.com/facebook/rocksdb/pull/2194
Differential Revision: D4929799
Pulled By: siying
fbshipit-source-id: 5cd49c254737a1d5ac13f3c035f128e86524c581
Summary:
Replace Options::use_direct_writes with Options::use_direct_io_for_flush_and_compaction
Now if Options::use_direct_io_for_flush_and_compaction = true, we will enable direct io for both reads and writes for flush and compaction job. Whereas Options::use_direct_reads controls user reads like iterator and Get().
Closes https://github.com/facebook/rocksdb/pull/2117
Differential Revision: D4860912
Pulled By: lightmark
fbshipit-source-id: d93575a8a5e780cf7e40797287edc425ee648c19
Summary:
Moved MergeOperatorPinning tests from db_test2.cc to db_merge_operator_test.cc.
[This is the same code as PR #2104 , which has already been reviewed, but I am creating a new PR as I cannot import from #2104 onto phabricator anymore even after rebasing. I'll close and discard #2104.]
Closes https://github.com/facebook/rocksdb/pull/2125
Differential Revision: D4863312
Pulled By: sagar0
fbshipit-source-id: 0f71a7690aa09c1d03ee85ce2bc1d2d89e4f4399
Summary:
Previously, when DB write buffer size triggers, we always pick the CF with most data in its memtable to flush. This approach can minimize total flush happens. Change the behavior to always pick the oldest unflushed CF, which makes it the same behavior when max_total_wal_size hits. This approach will minimize size used by max_total_wal_size.
Closes https://github.com/facebook/rocksdb/pull/1987
Differential Revision: D4703214
Pulled By: siying
fbshipit-source-id: 9ff8b09
Summary:
This PR is to support a way to iterate over all the keys that are just in memtables.
Closes https://github.com/facebook/rocksdb/pull/1953
Differential Revision: D4663500
Pulled By: sagar0
fbshipit-source-id: 144e177
Summary:
we occasionally missing this call so the file size will be wrong
Closes https://github.com/facebook/rocksdb/pull/1894
Differential Revision: D4598446
Pulled By: lightmark
fbshipit-source-id: 42b6ef5
Summary:
introduce new methods into a public threadpool interface,
- allow submission of std::functions as they allow greater flexibility.
- add Joining methods to the implementation to join scheduled and submitted jobs with
an option to cancel jobs that did not start executing.
- Remove ugly `#ifdefs` between pthread and std implementation, make it uniform.
- introduce pimpl for a drop in replacement of the implementation
- Introduce rocksdb::port::Thread typedef which is a replacement for std::thread. On Posix Thread defaults as before std::thread.
- Implement WindowsThread that allocates memory in a more controllable manner than windows std::thread with a replaceable implementation.
- should be no functionality changes.
Closes https://github.com/facebook/rocksdb/pull/1823
Differential Revision: D4492902
Pulled By: siying
fbshipit-source-id: c74cb11
Summary:
In theory, Get() can get a wrong result, if it races in a special with with flush. The bug can be reproduced in DBTest2.GetRaceFlush. Fix this bug by getting snapshot after referencing the super version.
Closes https://github.com/facebook/rocksdb/pull/1816
Differential Revision: D4475958
Pulled By: siying
fbshipit-source-id: bd9e67a
Summary:
A current data race issue in Get() and Flush() can cause a Get() to return wrong results when a flush happened in the middle. Disable the test for now.
Closes https://github.com/facebook/rocksdb/pull/1813
Differential Revision: D4472310
Pulled By: siying
fbshipit-source-id: 5755ebd
Summary:
If users directly call OptimizeForPointLookup(), it is broken as the option isn't compatible with parallel memtable insert. Fix it by using memtable bloomo filter instead.
Closes https://github.com/facebook/rocksdb/pull/1791
Differential Revision: D4442836
Pulled By: siying
fbshipit-source-id: bf6c9cd
Summary:
Exposing persistent cache stats (counters) to the user via public API.
Closes https://github.com/facebook/rocksdb/pull/1485
Differential Revision: D4155274
Pulled By: siying
fbshipit-source-id: 30a9f50
Summary:
Currently the compaction stats are printed to stdout. We want to export the compaction stats in a map format so that the upper layer apps (e.g., MySQL) could present
the stats in any format required by the them.
Closes https://github.com/facebook/rocksdb/pull/1477
Differential Revision: D4149836
Pulled By: maysamyabandeh
fbshipit-source-id: b3df19f
Summary:
Issue scenario:
(1) We have 3 files in L1 and we issue a compaction that will compact them into 1 file in L2
(2) While compaction (1) is running, we flush a file into L0 and trigger another compaction that decide to move this file to L1 and then move it again to L2 (this file don't overlap with any other files)
(3) compaction (1) finishes and install the file it generated in L2, but this file overlap with the file we generated in (2) so we break the LSM consistency
Looks like this issue can be triggered by using non-exclusive manual compaction or AddFile()
Test Plan: unit tests
Reviewers: sdong
Reviewed By: sdong
Subscribers: hermanlee4, jkedgar, andrewkr, dhruba, yoshinorim
Differential Revision: https://reviews.facebook.net/D64947
Summary:
Mitigate regression bug of options.max_successive_merges hit during DB Recovery
For https://reviews.facebook.net/D62625
Test Plan: make all check
Reviewers: horuff, sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D62655
Summary: Currently the WAL file preallocation size is 1.1 * write_buffer_size. This, however, will be over-estimated if options.db_write_buffer_size or options.max_total_wal_size is set and is much smaller.
Test Plan: Add a unit test.
Reviewers: andrewkr, yiwu
Reviewed By: yiwu
Subscribers: leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D63957
Summary:
ZSTD 1.0.0 is coming. We can finally add a support of ZSTD without worrying about compatibility.
Still keep ZSTDNotFinal for compatibility reason.
Test Plan: Run all tests. Run db_bench with ZSTD version with RocksDB built with ZSTD 1.0 and older.
Reviewers: andrewkr, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: cyan, igor, IslamAbdelRahman, leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D63141
Summary: To reduce number of options, merge source_compaction_factor, max_grandparent_overlap_bytes and expanded_compaction_factor into max_compaction_bytes.
Test Plan: Add two new unit tests. Run all existing tests, including jtest.
Reviewers: yhchiang, igor, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D59829
Summary:
Add ReadOptions::read_amp_bytes_per_bit option which allow us to create a bitmap for every data block we read
the bitmap will contain (block_size / read_amp_bytes_per_bit) bits.
We will use this bitmap to mark which bytes have been used of the block so we can calculate the read amplification
Test Plan: added new tests
Reviewers: andrewkr, yhchiang, sdong
Reviewed By: sdong
Subscribers: yiwu, leveldb, march, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D58707
Summary:
After 1b8a2e8fdd, DB Pointer is passed to WriteBatchInternal::InsertInto() while DB recovery. This can cause deadlock if options.max_successive_merges hits. In that case DB::Get() will be called. Get() will try to acquire the DB mutex, which is already held by the DB::Open(), causing a deadlock condition.
This commit mitigates the problem by not passing the DB pointer unless 2PC is allowed.
Test Plan: Add a new test and run it.
Reviewers: IslamAbdelRahman, andrewkr, kradhakrishnan, horuff
Reviewed By: kradhakrishnan
Subscribers: leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D62625
Summary:
This diff update ForwardIterator to support pinning keys and values, which will allow DBIter to take advantage of that and eliminate memcpy when executing merge operators
This diff is stacked on D61305
Test Plan:
existing tests (updated them to test tailing iterator)
new test
Reviewers: andrewkr, yhchiang, sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D60009
Summary: In T8216281 we decided to disable prefetching the index and filter during opening table handlers during startup (max_open_files = -1).
Test Plan: Rely on `IndexAndFilterBlocksOfNewTableAddedToCache` to guarantee L0 indexes and filters are still cached and change `PinL0IndexAndFilterBlocksTest` to make sure other levels are not cached (maybe add one more test to test we don't cache other levels?)
Reviewers: sdong, andrewkr
Reviewed By: andrewkr
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D59913
Summary: Add markers to sync points. A marked sync point will only be active when it is on the same thread as the marker sync point.
Test Plan: Write a unit test to validate.
Reviewers: sdong, IslamAbdelRahman, andrewkr
Reviewed By: andrewkr
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D60375
Summary: Add option write_buffer_manager to help users control total memory spent on memtables across multiple DB instances.
Test Plan: Add a new unit test.
Reviewers: yhchiang, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: adela, benj, sumeet, muthu, leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D59925
Summary:
NotifyOnCompactionCompleted can unlock the mutex.
That mean that we can schedule a background compaction that will start before we ReleaseCompactionFiles().
Test Plan:
added unittest
existing unittest
Reviewers: yhchiang, sdong
Reviewed By: sdong
Subscribers: yoshinorim, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D58065
Summary:
Added a new abstraction to cache page to RocksDB designed for the read
cache use.
RocksDB current block cache is more of an object cache. For the persistent read cache
project, what we need is a page cache equivalent. This changes adds a cache
abstraction to RocksDB to cache pages called PersistentCache. PersistentCache can cache
uncompressed pages or raw pages (content as in filesystem). The user can
choose to operate PersistentCache either in COMPRESSED or UNCOMPRESSED mode.
Blame Rev:
Test Plan: Run unit tests
Reviewers: sdong
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D55707
Summary:
Add a new option that can be used to set a specific compression algorithm for bottommost level.
This option will only affect levels larger than base level.
I have also updated CompactionJobInfo to include the compression algorithm used in compaction
Test Plan:
added new unittest
existing unittests
Reviewers: andrewkr, yhchiang, sdong
Reviewed By: sdong
Subscribers: lightmark, andrewkr, dhruba, yoshinorim
Differential Revision: https://reviews.facebook.net/D57669
Summary:
This test relies on "rocksdb.num-files-at-levelN" property that isn't
implemented in rocksdb lite. So we will compile it only for non-lite builds.
Test Plan:
$ make -j40 check 'OPT=-g -DROCKSDB_LITE'
Reviewers: sdong, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D57387
Summary:
There was one narrowing conversion in D52287 that only showed up with
clang on osx.
Test Plan:
$ make clean && USE_CLANG=1 DISABLE_JEMALLOC=1 TEST_TMPDIR=/dev/shm/rocksdb OPT=-g make -j32 check
Reviewers: sdong, lightmark, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D57357
Summary:
This adds a new metablock containing a shared dictionary that is used
to compress all data blocks in the SST file. The size of the shared dictionary
is configurable in CompressionOptions and defaults to 0. It's currently only
used for zlib/lz4/lz4hc, but the block will be stored in the SST regardless of
the compression type if the user chooses a nonzero dictionary size.
During compaction, computes the dictionary by randomly sampling the first
output file in each subcompaction. It pre-computes the intervals to sample
by assuming the output file will have the maximum allowable length. In case
the file is smaller, some of the pre-computed sampling intervals can be beyond
end-of-file, in which case we skip over those samples and the dictionary will
be a bit smaller. After the dictionary is generated using the first file in a
subcompaction, it is loaded into the compression library before writing each
block in each subsequent file of that subcompaction.
On the read path, gets the dictionary from the metablock, if it exists. Then,
loads that dictionary into the compression library before reading each block.
Test Plan: new unit test
Reviewers: yhchiang, IslamAbdelRahman, cyan, sdong
Reviewed By: sdong
Subscribers: andrewkr, yoshinorim, kradhakrishnan, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D52287
Summary:
Solution is not to change db sequence number to start from 1 because 0 value is used in multiple other places.
Fix covers only compact_iterator::findEarliestVisibleSnapshot with updated logic to support snapshot's numbering starting from 0.
Test Plan:
run:
make all check
it should pass all tests
Reviewers: IslamAbdelRahman, sdong
Reviewed By: sdong
Subscribers: lgalanis, mgalushka, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D56601
Summary:
In the case where we can't find a filter block, there is not much benefit of doing the binary search and see whether the index key has the prefix. With the change, we blindly return true if we can't get the filter.
It also fixes missing row cases for reverse comparator with full bloom.
Test Plan: Add a test case that used to fail.
Reviewers: yhchiang, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: kradhakrishnan, yiwu, hermanlee4, yoshinorim, leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D56697
Summary:
Full block checking should be a good enough indication of prefix existance. No need to further check data block.
This also fixes wrong results when using prefix bloom and reverse bitwise comparator.
Test Plan: Will add a unit test.
Reviewers: yhchiang, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: hermanlee4, yoshinorim, yiwu, kradhakrishnan, leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D56625
Summary:
When a block based table file is opened, if prefetch_index_and_filter is true, it will prefetch the index and filter blocks, putting them into the block cache.
What this feature adds: when a L0 block based table file is opened, if pin_l0_filter_and_index_blocks_in_cache is true in the options (and prefetch_index_and_filter is true), then the filter and index blocks aren't released back to the block cache at the end of BlockBasedTableReader::Open(). Instead the table reader takes ownership of them, hence pinning them, ie. the LRU cache will never push them out. Meanwhile in the table reader, further accesses will not hit the block cache, thus avoiding lock contention.
Test Plan:
'export TEST_TMPDIR=/dev/shm/ && DISABLE_JEMALLOC=1 OPT=-g make all valgrind_check -j32' is OK.
I didn't run the Java tests, I don't have Java set up on my devserver.
Reviewers: sdong
Reviewed By: sdong
Subscribers: andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D56133
Summary:
I ran into this assert when stress testing transactions. It's pretty easy to repro.
Changing VersionSet::last_sequence_ to start at 1 seems pretty straightforward. We would just need to change the 4 callers of SetLastSequence(), including recovery code. I'd make this change myself, but I do not have enough time to test changes to recovery code-paths this week. But checking in this test case (disabled) for future fixing.
Test Plan: n/a
Reviewers: yhchiang, kradhakrishnan, andrewkr, anthony, IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: andrewkr, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D55311
Summary:
In block based table reader, wow we put index reader to block cache, which can be retrieved after DB restart. However, index reader may reference internal comparator, which can be destroyed after DB restarts, causing problems.
Fix it by making cache key identical per table reader.
Test Plan: Add a new test which failed with out the commit but now pass.
Reviewers: IslamAbdelRahman
Reviewed By: IslamAbdelRahman
Subscribers: maro, yhchiang, kradhakrishnan, leveldb, andrewkr, dhruba
Differential Revision: https://reviews.facebook.net/D55287
Summary: I realized I again is wrong about the naming convention. Let me change it to the correct one.
Test Plan: Run unit tests.
Reviewers: IslamAbdelRahman, kradhakrishnan, yhchiang, andrewkr
Reviewed By: andrewkr
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D55041
Summary: We want to provide a way to detect whether an iterator is stale and needs to be recreated. Add a iterator property to return version number.
Test Plan: Add two unit tests for it.
Reviewers: IslamAbdelRahman, yhchiang, anthony, kradhakrishnan, andrewkr
Reviewed By: andrewkr
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D54921
