Summary:
- Summary
Add timestamp into the DeadlockInfo to store the timestamp when deadlock detected on the rocksdb side.
- Testplan:
`make check -j64`
Closes https://github.com/facebook/rocksdb/pull/4060
Differential Revision: D8655380
Pulled By: chouxi
fbshipit-source-id: f58e1aa5e09eb1d1eed0a181d4e2304aaf01efe8
Summary:
This is implemented by extending ReadCallback with another function `MaxUnpreparedSequenceNumber` which returns the largest visible sequence number for the current transaction, if there is uncommitted data written to DB. Otherwise, it returns zero, indicating no uncommitted data.
There are the places where reads had to be modified.
- Get and Seek/Next was just updated to seek to max(snapshot_seq, MaxUnpreparedSequenceNumber()) instead, and iterate until a key was visible.
- Prev did not need need updates since it did not use the Seek to sequence number optimization. Assuming that locks were held when writing unprepared keys, and ValidateSnapshot runs, there should only be committed keys and unprepared keys of the current transaction, all of which are visible. Prev will simply iterate to get the last visible key.
- Reseeking to skip keys optimization was also disabled for write unprepared, since it's possible to hit the max_skip condition even while reseeking. There needs to be some way to resolve infinite looping in this case.
Closes https://github.com/facebook/rocksdb/pull/3955
Differential Revision: D8286688
Pulled By: lth
fbshipit-source-id: 25e42f47fdeb5f7accea0f4fd350ef35198caafe
Summary:
As titled.
I have not extended the Compatibility tests because the new WAL markers are still unimplemented.
Closes https://github.com/facebook/rocksdb/pull/3941
Differential Revision: D8238394
Pulled By: lth
fbshipit-source-id: 980e3d44837bbf2cfa64047f9738f559dfac4b1d
Summary:
In order to make valgrind check test to pass in a day, remove some tests that run prohibitively slow under valgrind.
Closes https://github.com/facebook/rocksdb/pull/3924
Differential Revision: D8210184
Pulled By: siying
fbshipit-source-id: 5b06fb08f3cf57571d422d05a0dbddc9f9376f7a
Summary:
The patch clarifies the ownership of the root db after TransactionDB::Open. If it is a success the ownership if with the TransactionDB, and the root db will be deleted when the destructor of the base class, StackableDB, is called. If it is failure, the temporarily created root db will also be deleted properly.
The patch also includes lots of useful formatting changes.
Closes https://github.com/facebook/rocksdb/pull/3714 upon which this patch is built.
Closes https://github.com/facebook/rocksdb/pull/3806
Differential Revision: D7878010
Pulled By: maysamyabandeh
fbshipit-source-id: f54f3942e29434143ae5a2423ceec9c7072cd4c2
Summary:
This patch record min log number to keep to the manifest while flushing SST files to ignore them and any WAL older than them during recovery. This is to avoid scenarios when we have a gap between the WAL files are fed to the recovery procedure. The gap could happen by for example out-of-order WAL deletion. Such gap could cause problems in 2PC recovery where the prepared and commit entry are placed into two separate WAL and gap in the WALs could result into not processing the WAL with the commit entry and hence breaking the 2PC recovery logic.
Before the commit, for 2PC case, we determined which log number to keep in FindObsoleteFiles(). We looked at the earliest logs with outstanding prepare entries, or prepare entries whose respective commit or abort are in memtable. With the commit, the same calculation is done while we apply the SST flush. Just before installing the flush file, we precompute the earliest log file to keep after the flush finishes using the same logic (but skipping the memtables just flushed), record this information to the manifest entry for this new flushed SST file. This pre-computed value is also remembered in memory, and will later be used to determine whether a log file can be deleted. This value is unlikely to change until next flush because the commit entry will stay in memtable. (In WritePrepared, we could have removed the older log files as soon as all prepared entries are committed. It's not yet done anyway. Even if we do it, the only thing we loss with this new approach is earlier log deletion between two flushes, which does not guarantee to happen anyway because the obsolete file clean-up function is only executed after flush or compaction)
This min log number to keep is stored in the manifest using the safely-ignore customized field of AddFile entry, in order to guarantee that the DB generated using newer release can be opened by previous releases no older than 4.2.
Closes https://github.com/facebook/rocksdb/pull/3765
Differential Revision: D7747618
Pulled By: siying
fbshipit-source-id: d00c92105b4f83852e9754a1b70d6b64cb590729
Summary:
Rollback was disabled in stress test since there was a concurrency issue in WritePrepared rollback algorithm. The issue is fixed by caching the column family handles in WritePrepared to skip getting them from the db when needed for rollback.
Tested by running transaction stress test under tsan.
Closes https://github.com/facebook/rocksdb/pull/3785
Differential Revision: D7793727
Pulled By: maysamyabandeh
fbshipit-source-id: d81ab6fda0e53186ca69944cfe0712ce4869451e
Summary:
The tsan flavor of SeqAdvanceConcurrentTest times out in our test infra. The patch splits it into 10 tests.
On my vm before:
[ OK ] WritePreparedTransactionTest/WritePreparedTransactionTest.SeqAdvanceConcurrentTest/0 (5194 ms)
after:
[ OK ] OneWriteQueue/SeqAdvanceConcurrentTest.SeqAdvanceConcurrentTest/0 (1906 ms)
Closes https://github.com/facebook/rocksdb/pull/3799
Differential Revision: D7854515
Pulled By: maysamyabandeh
fbshipit-source-id: 4fbac42a1f974326cbc237f8cb9d6232d379c431
Summary:
Currently WritePrepared rolls back a transaction with prepare sequence number prepare_seq by i) write a single rollback batch with rollback_seq, ii) add <rollback_seq, rollback_seq> to commit cache, iii) remove prepare_seq from PrepareHeap.
This is correct assuming that there is no snapshot taken when a transaction is rolled back. This is the case the way MySQL does rollback which is after recovery. Otherwise if max_evicted_seq advances the prepare_seq, the live snapshot might assume data as committed since it does not find them in CommitCache.
The change is to simply add <prepare_seq. rollback_seq> to commit cache before removing prepare_seq from PrepareHeap. In this way if max_evicted_seq advances prpeare_seq, the existing mechanism that we have to check evicted entries against live snapshots will make sure that the live snapshot will not see the data of rolled back transaction.
Closes https://github.com/facebook/rocksdb/pull/3745
Differential Revision: D7696193
Pulled By: maysamyabandeh
fbshipit-source-id: c9a2d46341ddc03554dded1303520a1cab74ef9c
Summary:
The WriteBatch::Iterate will try with a larger sequence number if the memtable reports a duplicate. This status is specified with TryAgain status. So far the assumption was that the last entry in the batch will never return TryAgain, which is correct when WAL is created via WritePrepared since it always appends a batch separator if a natural one does not exist. However when reading a WAL generated by WriteCommitted this batch separator might not exist. Although WritePrepared is not supposed to be able to read the WAL generated by WriteCommitted we should avoid confusing scenarios in which the behavior becomes unpredictable. The path fixes that by allowing TryAgain even for the last entry of the write batch.
Closes https://github.com/facebook/rocksdb/pull/3747
Differential Revision: D7708391
Pulled By: maysamyabandeh
fbshipit-source-id: bfaddaa9b14a4cdaff6977f6f63c789a6ab1ee0d
Summary:
this PR fixes a few failed contbuild:
1. ASAN memory leak in Block::NewIterator (table/block.cc:429). the proper destruction of first_level_iter_ and second_level_iter_ of two_level_iterator.cc is missing from the code after the refactoring in https://github.com/facebook/rocksdb/pull/3406
2. various unused param errors introduced by https://github.com/facebook/rocksdb/pull/3662
3. updated comment for `ForceReleaseCachedEntry` to emphasize the use of `force_erase` flag.
Closes https://github.com/facebook/rocksdb/pull/3718
Reviewed By: maysamyabandeh
Differential Revision: D7621192
Pulled By: miasantreble
fbshipit-source-id: 476c94264083a0730ded957c29de7807e4f5b146
Summary:
This PR comments out the rest of the unused arguments which allow us to turn on the -Wunused-parameter flag. This is the second part of a codemod relating to https://github.com/facebook/rocksdb/pull/3557.
Closes https://github.com/facebook/rocksdb/pull/3662
Differential Revision: D7426121
Pulled By: Dayvedde
fbshipit-source-id: 223994923b42bd4953eb016a0129e47560f7e352
Summary:
This is a hack as temporary fix of MyRocks with rollbacking the merge operands. The way MyRocks uses merge operands is without protection of locks, which violates the assumption behind the rollback algorithm. They are ok with not being rolled back as it would just create a gap in the autoincrement column. The hack add an option to disable the rollback of merge operands by default and only enables it to let the unit test pass.
Closes https://github.com/facebook/rocksdb/pull/3711
Differential Revision: D7597177
Pulled By: maysamyabandeh
fbshipit-source-id: 544be0f666c7e7abb7f651ec8b23124e05056728
Summary:
We introduced smallest_prep optimization in this commit b225de7e10, which enables storing the smallest uncommitted sequence number along with the snapshot. This enables the readers that read from the snapshot to skip further checks and safely assumed the data is committed if its sequence number is less than smallest uncommitted when the snapshot was taken. The problem was that smallest uncommitted and the snapshot must be taken atomically, and the lack of atomicity had led to readers using a smallest uncommitted after the snapshot was taken and hence mistakenly skipping some data.
This patch fixes the problem by i) separating the process of removing of prepare entries from the AddCommitted function, ii) removing the prepare entires AFTER the committed sequence number is published, iii) getting smallest uncommitted (from the prepare list) BEFORE taking a snapshot. This guarantees that the smallest uncommitted that is accompanied with a snapshot is less than or equal of such number if it was obtained atomically.
Tested by running MySQLStyleTransactionTest/MySQLStyleTransactionTest.TransactionStressTest that was failing sporadically.
Closes https://github.com/facebook/rocksdb/pull/3703
Differential Revision: D7581934
Pulled By: maysamyabandeh
fbshipit-source-id: dc9d6f4fb477eba75d4d5927326905b548a96a32
Summary:
Adding some stats that would be helpful to monitor if the DB has gone to unlikely stats that would hurt the performance. These are mostly when we end up needing to acquire a mutex.
Closes https://github.com/facebook/rocksdb/pull/3683
Differential Revision: D7529393
Pulled By: maysamyabandeh
fbshipit-source-id: f7d36279a8f39bd84d8ddbf64b5c97f670c5d6d9
Summary:
This change models Optimistic Tx db after Pessimistic TX db. The motivation for this change is to make the ptr polymorphic so it can be held by the same raw or smart ptr.
Currently, due to the inheritance of the Opt Tx db not being rooted in the manner of Pess Tx from a single DB root it is more difficult to write clean code and have clear ownership of the database in cases when options dictate instantiate of plan DB, Pess Tx DB or Opt tx db.
Closes https://github.com/facebook/rocksdb/pull/3566
Differential Revision: D7184502
Pulled By: yiwu-arbug
fbshipit-source-id: 31d06efafd79497bb0c230e971857dba3bd962c3
Summary:
The is an optimization to reduce lookup in the CommitCache when querying IsInSnapshot. The optimization takes the smallest uncommitted data at the time that the snapshot was taken and if the sequence number of the read data is lower than that number it assumes the data as committed.
To implement this optimization two changes are required: i) The AddPrepared function must be called sequentially to avoid out of order insertion in the PrepareHeap (otherwise the top of the heap does not indicate the smallest prepare in future too), ii) non-2PC transactions also call AddPrepared if they do not commit in one step.
Closes https://github.com/facebook/rocksdb/pull/3649
Differential Revision: D7388630
Pulled By: maysamyabandeh
fbshipit-source-id: b79506238c17467d590763582960d4d90181c600
Summary:
Currently if the CommitTimeWriteBatch is set to be used only as a state that is required only for recovery , the user cannot see that in DB until it is restarted. This while the state is already inserted into the DB after the memtable flush. It would be useful for debugging if make this state visible to the user after the flush by committing it. The patch does it by a invoking a callback that does the commit on the recoverable state.
Closes https://github.com/facebook/rocksdb/pull/3661
Differential Revision: D7424577
Pulled By: maysamyabandeh
fbshipit-source-id: 137f9408662f0853938b33fa440f27f04c1bbf5c
Summary:
Current commit cache size is 2^21. This was due to a type. With 2^23 commit entries we can have transactions as long as 64s without incurring the cost of having them evicted from the commit cache before their commit. Here is the math:
2^23 / 2 (one out of two seq numbers are for commit) / 2^16 TPS = 2^6 = 64s
Closes https://github.com/facebook/rocksdb/pull/3657
Differential Revision: D7411211
Pulled By: maysamyabandeh
fbshipit-source-id: e7cacf40579f3acf940643d8a1cfe5dd201caa35
Summary:
Currently AddPrepared is performed only on the first sub-batch if there are duplicate keys in the write batch. This could cause a problem if the transaction takes too long to commit and the seq number of the first sub-patch moved to old_prepared_ but not the seq of the later ones. The patch fixes this by calling AddPrepared for all sub-patches.
Closes https://github.com/facebook/rocksdb/pull/3651
Differential Revision: D7388635
Pulled By: maysamyabandeh
fbshipit-source-id: 0ccd80c150d9bc42fe955e49ddb9d7ca353067b4
Summary:
This commit fixes a race condition on calling SetLastPublishedSequence. The function must be called only from the 2nd write queue when two_write_queues is enabled. However there was a bug that would also call it from the main write queue if CommitTimeWriteBatch is provided to the commit request and yet use_only_the_last_commit_time_batch_for_recovery optimization is not enabled. To fix that we penalize the commit request in such cases by doing an additional write solely to publish the seq number from the 2nd queue.
Closes https://github.com/facebook/rocksdb/pull/3641
Differential Revision: D7361508
Pulled By: maysamyabandeh
fbshipit-source-id: bf8f7a27e5cccf5425dccbce25eb0032e8e5a4d7
Summary:
This patch addressed several issues.
Portability including db_test std::thread -> port::Thread Cc: @
and %z to ROCKSDB portable macro. Cc: maysamyabandeh
Implement Env::AreFilesSame
Make the implementation of file unique number more robust
Get rid of C-runtime and go directly to Windows API when dealing
with file primitives.
Implement GetSectorSize() and aling unbuffered read on the value if
available.
Adjust Windows Logger for the new interface, implement CloseImpl() Cc: anand1976
Fix test running script issue where $status var was of incorrect scope
so the failures were swallowed and not reported.
DestroyDB() creates a logger and opens a LOG file in the directory
being cleaned up. This holds a lock on the folder and the cleanup is
prevented. This fails one of the checkpoin tests. We observe the same in production.
We close the log file in this change.
Fix DBTest2.ReadAmpBitmapLiveInCacheAfterDBClose failure where the test
attempts to open a directory with NewRandomAccessFile which does not
work on Windows.
Fix DBTest.SoftLimit as it is dependent on thread timing. CC: yiwu-arbug
Closes https://github.com/facebook/rocksdb/pull/3552
Differential Revision: D7156304
Pulled By: siying
fbshipit-source-id: 43db0a757f1dfceffeb2b7988043156639173f5b
Summary:
Move DuplicateDetector and SetComparator to its own header file in util. It would also address a complaint in the unity test.
Closes https://github.com/facebook/rocksdb/pull/3567
Differential Revision: D7163268
Pulled By: maysamyabandeh
fbshipit-source-id: 6ddf82773473646dbbc1284ae601a78c4907c778
Summary:
Fix the following bugs:
- During recovery a duplicate key was inserted twice into the write batch of the recovery transaction,
once when the memtable returns false (because it was duplicates) and once for the 2nd attempt. This would result into different SubBatch count measured when the recovered transactions is committing.
- If a cf is flushed during recovery the memtable is not available to assist in detecting the duplicate key. This could result into not advancing the sequence number when iterating over duplicate keys of a flushed cf and hence inserting the next key with the wrong sequence number.
- SubBacthCounter would reset the comparator to default comparator after the first duplicate key. The 2nd duplicate key hence would have gone through a wrong comparator and not being detected.
Closes https://github.com/facebook/rocksdb/pull/3562
Differential Revision: D7149440
Pulled By: maysamyabandeh
fbshipit-source-id: 91ec317b165f363f5d11ff8b8c47c81cebb8ed77
Summary:
The zeroed entries were not removed from prepared_section_completed_ map. This patch adds a unit test to show the problem and fixes that by refactoring the code. The new code is more efficient since i) it uses two separate mutex to avoid contention between commit and prepare threads, ii) it uses a sorted vector for maintaining uniq log entires with prepare which avoids a very large heap with many duplicate entries.
Closes https://github.com/facebook/rocksdb/pull/3545
Differential Revision: D7106071
Pulled By: maysamyabandeh
fbshipit-source-id: b3ae17cb6cd37ef10b6b35e0086c15c758768a48
Summary:
Make use of the index in WriteBatchWithIndex to also count the number of sub-batches. This eliminates the need to separately scan the batch to count the number of sub-batches once a duplicate key is detected.
Closes https://github.com/facebook/rocksdb/pull/3529
Differential Revision: D7049947
Pulled By: maysamyabandeh
fbshipit-source-id: 81cbf12c4e662541c772c7265a8f91631e25c7cd
Summary:
Under a certain sequence of accessing PreparedHeap, there was a bug that would not successfully empty the heap. This would result in performance issues when the heap content is moved to old_prepared_ after max_evicted_seq_ advances the orphan prepared sequence numbers. The patch fixed the bug and add more unit tests. It also does more logging when the unlikely scenarios are faced
Closes https://github.com/facebook/rocksdb/pull/3526
Differential Revision: D7038486
Pulled By: maysamyabandeh
fbshipit-source-id: f1e40bea558f67b03d2a29131fcb8734c65fce97
Summary:
In case it is found that a key is already marked as locked in a
stripe's map of locked keys, it is not necessary to look it up
again using `std::unordered_map<std::string, ...>::at(size_t)`.
Instead, we can use the already found position using the iterator
produced by the previous `find` operation. Reusing the iterator
will avoid having to hash the key again and do additional "random"
memory lookups in the map of keys (though the data will very
likely sit available in caches here already due to the previous
find operation)
Closes https://github.com/facebook/rocksdb/pull/3505
Differential Revision: D7036446
Pulled By: sagar0
fbshipit-source-id: cced51547b2bd2d49394f6bc8c5896f09fa80f68
Summary:
These are optimization that we applied to improve sysbech's update_noindex performance.
1. Make use of LIKELY compiler hint
2. Move std::atomic so the subclass
3. Make use of skip_prepared in non-2pc transactions.
Closes https://github.com/facebook/rocksdb/pull/3512
Differential Revision: D7000075
Pulled By: maysamyabandeh
fbshipit-source-id: 1ab8292584df1f6305a4992973fb1b7933632181
Summary:
- removed a few unneeded variables
- fused some variable declarations and their assignments
- fixed right-trimming code in string_util.cc to not underflow
- simplifed an assertion
- move non-nullptr check assertion before dereferencing of that pointer
- pass an std::string function parameter by const reference instead of by value (avoiding potential copy)
Closes https://github.com/facebook/rocksdb/pull/3507
Differential Revision: D7004679
Pulled By: sagar0
fbshipit-source-id: 52944952d9b56dfcac3bea3cd7878e315bb563c4
Summary:
TransactionDB::Write can receive some optimization hints from the user. One is to skip the concurrency control mechanism. WritePreparedTxnDB is currently ignoring such hints. This patch optimizes WritePreparedTxnDB::Write for skip_concurrency_control and skip_duplicate_key_check hints.
Closes https://github.com/facebook/rocksdb/pull/3496
Differential Revision: D6971784
Pulled By: maysamyabandeh
fbshipit-source-id: cbab10ad538fa2b8bcb47e37c77724afe6e30f03
Summary:
WritePreparedTransactionTest has the UBSAN error because the wrong order of its parent class construction. Fix it.
Closes https://github.com/facebook/rocksdb/pull/3478
Differential Revision: D6928975
Pulled By: siying
fbshipit-source-id: 13edfd5cb9cf73f1ac5ae3b6f53061d32783733d
Summary:
Compared to DB::Write, TransactionDB::Write has the additional overhead of creating and initializing an internal transaction object, as well as the overhead of locking/unlocking the keys. This patch extends the TransactionDB::Write with an skip_cc option to allow the users to indicate that the write batch do not conflict with others and the concurrency control and its overhead can be skipped. TransactionDB::Write by default calls DB::Write when skip_cc is set, which works for WriteCommitted WritePolicy. Any other flavor of TransactionDB that is not compatible with this default behavior (such as WritePreparedTxnDB) can extend ::Write and implement their own approach for taking into account the skip_cc optimization.
Closes https://github.com/facebook/rocksdb/pull/3457
Differential Revision: D6877318
Pulled By: maysamyabandeh
fbshipit-source-id: 56f4e21db87ff71492db4e376fb7c2b03dfeab6b
Summary:
Deletes the transaction object at the end of the test.
Verified by:
- COMPILE_WITH_ASAN=1 make -j32 transaction_test
- ./transaction_test --gtest_filter="DBA**Duplicate*"
Closes https://github.com/facebook/rocksdb/pull/3470
Differential Revision: D6916473
Pulled By: maysamyabandeh
fbshipit-source-id: 8303df25408635d5d3ac2b25f309a3d15957c937
Summary:
This patch takes advantage of memtable being able to detect duplicate <key,seq> and returning TryAgain to handle duplicate keys in WritePrepared Txns. Through WriteBatchWithIndex's index it detects existence of at least a duplicate key in the write batch. If duplicate key was reported, it then pays the cost of counting the number of sub-patches by iterating over the write batch and pass it to DBImpl::Write. DB will make use of the provided batch_count to assign proper sequence numbers before sending them to the WAL. When later inserting the batch to the memtable, it increases the seq each time memtbale reports a duplicate (a sub-patch in our counting) and tries again.
Closes https://github.com/facebook/rocksdb/pull/3455
Differential Revision: D6873699
Pulled By: maysamyabandeh
fbshipit-source-id: db8487526c3a5dc1ddda0ea49f0f979b26ae648d
Summary:
Without this patch, ubsan_check is currently failing with this error:
```
utilities/transactions/write_prepared_transaction_test.cc:369:63: runtime error: member call on address 0x0000051649f8 which does not point to an object of type 'WithParamInterface'
0x0000051649f8: note: object has invalid vptr
```
Tested by `COMPILE_WITH_UBSAN=1 make -j32 transaction_test` and running `./write_prepared_transaction_test --gtest_filter=TwoWriteQueues/SnapshotConcurrentAccessTest.SnapshotConcurrentAccessTest1/0`
Closes https://github.com/facebook/rocksdb/pull/3444
Differential Revision: D6850087
Pulled By: maysamyabandeh
fbshipit-source-id: 5b254da8504b8757f7aec8a820ad464154da1a1d
Summary:
SnapshotConcurrentAccessTest sometimes times out when running on the test infra. This patch splits the test into smaller sub-tests to avoid the timeout. It also benefits from lower run-time of each sub-test and increases the coverage of the test. The overall run-time of each final sub-test is at most half of the original test so we should no longer see a timeout.
Closes https://github.com/facebook/rocksdb/pull/3435
Differential Revision: D6839427
Pulled By: maysamyabandeh
fbshipit-source-id: d53fdb157109e2438ca7fe447d0cf4b71f304bd8
Summary:
This patch addresses a couple of minor TODOs for WritePrepared Txn such as double checking some assert statements at runtime as well, skip extra AddPrepared in non-2pc transactions, and safety check for infinite loops.
Closes https://github.com/facebook/rocksdb/pull/3302
Differential Revision: D6617002
Pulled By: maysamyabandeh
fbshipit-source-id: ef6673c139cb49f64c0879508d2f573b78609aca
Summary:
DestroyDB that is used in tests loops over the files returned by ::GetChildren and delete them one by one. Such files might be already deleted in the file system (during DeleteObsoleteFileImpl for example) but will get actually deleted with a delay sometimes before ::DeleteFile is called on the file name. We have some test failures where FaultInjectionTestEnv::DeleteFile fails on assert(s.ok()) during DestroyDB. This patch removes the assert statement to fix that.
Closes https://github.com/facebook/rocksdb/pull/3324
Differential Revision: D6659545
Pulled By: maysamyabandeh
fbshipit-source-id: 4c9552fbcd494dcf3e61d475c11fc965c4388b2c
Summary:
A proper implementation of Iterator::Refresh() for WritePreparedTxnDB would require release and acquire another snapshot. Since MyRocks don't make use of Iterator::Refresh(), we just simply mark it as not supported.
Closes https://github.com/facebook/rocksdb/pull/3290
Differential Revision: D6599931
Pulled By: yiwu-arbug
fbshipit-source-id: 4e1632d967316431424f6e458254ecf9a97567cf
Summary:
Currently non-2pc writes do the 2nd dummy write to actually commit the transaction. This was necessary to ensure that publishing the commit sequence number will be done only from one queue (the queue that does not write to memtable). This is however not necessary when we have only one write queue, which is actually the setup that would be used by non-2pc writes. This patch eliminates the 2nd write when two_write_queues are disabled by updating the commit map in the 1st write.
Closes https://github.com/facebook/rocksdb/pull/3277
Differential Revision: D6575392
Pulled By: maysamyabandeh
fbshipit-source-id: 8ab458f7ca506905962f9166026b2ec81e749c46
chouxi