Summary:
- Change directory name from "db_test" to "checkpoint_test". Previously it used the same directory as `db_test`
- Systematically cleanup snapshot and snapshot staging directories before each test. Previously a failed test run caused subsequent runs to fail, particularly when the first failure caused "snapshot.tmp" to not be cleaned up.
Closes https://github.com/facebook/rocksdb/pull/3351
Differential Revision: D6691015
Pulled By: ajkr
fbshipit-source-id: 4fc2ac2e21ff2617ea0e96297c5132b5f2eefd79
Summary:
Most popular versions of GCC can't identify platform on ARM if "-march=native" is specified. Remove it to unblock most people.
Closes https://github.com/facebook/rocksdb/pull/3346
Differential Revision: D6690544
Pulled By: siying
fbshipit-source-id: bbaba9fe2645b6b37144b36ea75beeff88992b49
Summary:
I experienced weird segfault because of this mismatch of type in log formatting. Fix it.
Closes https://github.com/facebook/rocksdb/pull/3345
Differential Revision: D6687224
Pulled By: siying
fbshipit-source-id: c51fb1c008b7ebc3efdc353a4adad3e8f5b3e9de
Summary:
got confused while reading `FindObsoleteFiles` due to thinking it's a local variable, so renamed it properly
Closes https://github.com/facebook/rocksdb/pull/3342
Differential Revision: D6684797
Pulled By: ajkr
fbshipit-source-id: a4df0aae1cccce99d4dd4d164aadc85b17707132
Summary:
The macro was added by mistake in #2372
Closes https://github.com/facebook/rocksdb/pull/3343
Differential Revision: D6681356
Pulled By: yiwu-arbug
fbshipit-source-id: 4180172fb0eaef4189c07f219241e0c261c03461
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:
Previously on a blob db read, we are making a read of the blob value, and then make another read to get CRC checksum. I'm combining the two read into one.
readrandom db_bench with 1G database with base db size of 13M, value size 1k:
`./db_bench --db=/home/yiwu/tmp/db_bench --use_blob_db --value_size=1024 --num=1000000 --benchmarks=readrandom --use_existing_db --cache_size=32000000`
master: throughput 234MB/s, get micros p50 5.984 p95 9.998 p99 20.817 p100 787
this PR: throughput 261MB/s, get micros p50 5.157 p95 9.928 p99 20.724 p100 190
Closes https://github.com/facebook/rocksdb/pull/3301
Differential Revision: D6615950
Pulled By: yiwu-arbug
fbshipit-source-id: 052410c6d8539ec0cc305d53793bbc8f3616baa3
Summary:
With the ZSTD dictionary generator support added in #3057
`PORTABLE=1 ROCKSDB_NO_FBCODE=1 make rocksdbjavastatic` fails as it can't find zdict.h. Specifically due to:
e3a06f12d2/util/compression.h (L39)
In java static builds zstd code gets directly downloaded from https://github.com/facebook/zstd , and in there zdict.h is under dictBuilder directory. So, I modified libzstd.a target to use `make install` to collect all the header files into a single location and used that as the zstd's include path.
Closes https://github.com/facebook/rocksdb/pull/3260
Differential Revision: D6669850
Pulled By: sagar0
fbshipit-source-id: f8a7562a670e5aed4c4fb6034a921697590d7285
Summary:
Make dependacies switches compatible with other OS builds
TODO: Make find_package work for Windows.
Closes https://github.com/facebook/rocksdb/pull/3322
Differential Revision: D6667637
Pulled By: sagar0
fbshipit-source-id: 5afcd7bbfe69465310a4fbc8e589f01e506b95f5
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:
added support for C and asm files as required for e612e31740.
Closes https://github.com/facebook/rocksdb/pull/3299
Differential Revision: D6612479
Pulled By: ajkr
fbshipit-source-id: 6263ed7c1602f249460421825c76b5721f396163
Summary:
BlockTest.BlockReadAmpBitmap is too slow and times out in some environments. Speed it up by:
(1) improve the way the verification is done. With this it is 5 times faster
(2) run fewer tests for large blocks. This cut it down by another 10 times.
Now it can finish in similar time as other tests.
Closes https://github.com/facebook/rocksdb/pull/3313
Differential Revision: D6643711
Pulled By: siying
fbshipit-source-id: c2397d666eab5421a78ca87e1e45491e0f832a6d
Summary:
FILE_FLAG_WRITE_THROUGH is for disabling device on-board cache in windows API, which should be disabled if user doesn't need system cache.
There was a perf issue related with this, we found during memtable flush, the high percentile latency jumps significantly. During profiling, we found those high latency (P99.9) read requests got queue-jumped by write requests from memtable flush and takes 80ms or even more time to wait, even when SSD overall IO throughput is relatively low.
After enabling FILE_FLAG_WRITE_THROUGH, we rerun the test found high percentile latency drops a lot without observable impact on writes.
Scenario 1: 40MB/s + 40MB/s R/W compaction throughput
 Original | FILE_FLAG_WRITE_THROUGH | Percentage reduction
---------------------------------------------------------------
P99.9 | 56.897 ms | 35.593 ms | -37.4%
P99 | 3.905 ms | 3.896 ms | -2.8%
Scenario 2: 14MB/s + 14MB/s R/W compaction throughput, cohosted with 100+ other rocksdb instances have manually triggered memtable flush operations (memtable is tiny), creating a lot of randomized the small file writes operations during test.
Original | FILE_FLAG_WRITE_THROUGH | Percentage reduction
---------------------------------------------------------------
P99.9 | 86.227 ms | 50.436 ms | -41.5%
P99 | 8.415 ms | 3.356 ms | -60.1%
Closes https://github.com/facebook/rocksdb/pull/3225
Differential Revision: D6624174
Pulled By: miasantreble
fbshipit-source-id: 321b86aee9d74470840c70e5d0d4fa9880660a91
Summary:
Fixes the following ASAN error:
```
==2108042==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7fc50ae9b868 at pc 0x7fc5112aff55 bp 0x7fff9eb9dc10 sp 0x7fff9eb9dc08
=== How to use this, how to get the raw stack trace, and more: fburl.com/ASAN ===
READ of size 8 at 0x7fc50ae9b868 thread T0
SCARINESS: 23 (8-byte-read-stack-use-after-scope)
#0 rocksdb/dbformat.h:164 rocksdb::InternalKeyComparator::user_comparator() const
#1 librocksdb_src_rocksdb_lib.so+0x1429a7d rocksdb::RangeDelAggregator::InitRep(std::vector<...> const&)
#2 librocksdb_src_rocksdb_lib.so+0x142ceae rocksdb::RangeDelAggregator::AddTombstones(std::unique_ptr<...>)
#3 librocksdb_src_rocksdb_lib.so+0x1382d88 rocksdb::ForwardIterator::RebuildIterators(bool)
#4 librocksdb_src_rocksdb_lib.so+0x1382362 rocksdb::ForwardIterator::ForwardIterator(rocksdb::DBImpl*, rocksdb::ReadOptions const&, rocksdb::ColumnFamilyData*, rocksdb::SuperVersion*)
#5 librocksdb_src_rocksdb_lib.so+0x11f433f rocksdb::DBImpl::NewIterator(rocksdb::ReadOptions const&, rocksdb::ColumnFamilyHandle*)
#6 rocksdb/src/include/rocksdb/db.h:382 rocksdb::DB::NewIterator(rocksdb::ReadOptions const&)
#7 rocksdb/db_range_del_test.cc:807 rocksdb::DBRangeDelTest_TailingIteratorRangeTombstoneUnsupported_Test::TestBody()
#18 rocksdb/db_range_del_test.cc:1006 main
Address 0x7fc50ae9b868 is located in stack of thread T0 at offset 104 in frame
#0 librocksdb_src_rocksdb_lib.so+0x13825af rocksdb::ForwardIterator::RebuildIterators(bool)
```
Closes https://github.com/facebook/rocksdb/pull/3300
Differential Revision: D6612989
Pulled By: ajkr
fbshipit-source-id: e7ea2ed914c1b80a8a29d71d92440a6bd9cbcc80
Summary:
Blog post to introduce the next generation of transaction engine at RocksDB.
Closes https://github.com/facebook/rocksdb/pull/3296
Differential Revision: D6612932
Pulled By: maysamyabandeh
fbshipit-source-id: 5bfa91ce84e937f5e4346bbda5a4725d0a7fd131
Summary:
When there is a background error PreprocessWrite returns without marking the logs synced. If we keep need_log_sync to true, it would try to sync them at the end, which would break the logic. The patch would unset need_log_sync if the logs end up not being marked for sync in PreprocessWrite.
Closes https://github.com/facebook/rocksdb/pull/3293
Differential Revision: D6602347
Pulled By: maysamyabandeh
fbshipit-source-id: 37ee04209e8dcfd78de891654ce50d0954abeb38
Summary:
This fixes the following warnings when compiled with GCC7:
util/transaction_test_util.cc: In static member function ‘static rocksdb::Status rocksdb::RandomTransactionInserter::DBGet(rocksdb::DB*, rocksdb::Transaction*, rocksdb::ReadOptions&, uint16_t, uint64_t, bool, uint64_t*, std::__cxx11::string*, bool*)’:
util/transaction_test_util.cc:75:8: error: ‘snprintf’ output may be truncated before the last format character [-Werror=format-truncation=]
Status RandomTransactionInserter::DBGet(
^~~~~~~~~~~~~~~~~~~~~~~~~
util/transaction_test_util.cc:84:11: note: ‘snprintf’ output between 5 and 6 bytes into a destination of size 5
snprintf(prefix_buf, sizeof(prefix_buf), "%.4u", set_i + 1);
~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
util/transaction_test_util.cc: In static member function ‘static rocksdb::Status rocksdb::RandomTransactionInserter::Verify(rocksdb::DB*, uint16_t, uint64_t, bool, rocksdb::Random64*)’:
util/transaction_test_util.cc:245:8: error: ‘snprintf’ output may be truncated before the last format character [-Werror=format-truncation=]
Status RandomTransactionInserter::Verify(DB* db, uint16_t num_sets,
^~~~~~~~~~~~~~~~~~~~~~~~~
util/transaction_test_util.cc:268:13: note: ‘snprintf’ output between 5 and 6 bytes into a destination of size 5
snprintf(prefix_buf, sizeof(prefix_buf), "%.4u", set_i + 1);
~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Closes https://github.com/facebook/rocksdb/pull/3295
Differential Revision: D6609411
Pulled By: maysamyabandeh
fbshipit-source-id: 33f0add471056eb59db2f8bd4366e6dfbb1a187d
Summary:
**# Summary**
RocksDB uses SSE crc32 intrinsics to calculate the crc32 values but it does it in single way fashion (not pipelined on single CPU core). Intel's whitepaper () published an algorithm that uses 3-way pipelining for the crc32 intrinsics, then use pclmulqdq intrinsic to combine the values. Because pclmulqdq has overhead on its own, this algorithm will show perf gains on buffers larger than 216 bytes, which makes RocksDB a perfect user, since most of the buffers RocksDB call crc32c on is over 4KB. Initial db_bench show tremendous CPU gain.
This change uses the 3-way SSE algorithm by default. The old SSE algorithm is now behind a compiler tag NO_THREEWAY_CRC32C. If user compiles the code with NO_THREEWAY_CRC32C=1 then the old SSE Crc32c algorithm would be used. If the server does not have SSE4.2 at the run time the slow way (Non SSE) will be used.
**# Performance Test Results**
We ran the FillRandom and ReadRandom benchmarks in db_bench. ReadRandom is the point of interest here since it calculates the CRC32 for the in-mem buffers. We did 3 runs for each algorithm.
Before this change the CRC32 value computation takes about 11.5% of total CPU cost, and with the new 3-way algorithm it reduced to around 4.5%. The overall throughput also improved from 25.53MB/s to 27.63MB/s.
1) ReadRandom in db_bench overall metrics
PER RUN
Algorithm | run | micros/op | ops/sec |Throughput (MB/s)
3-way | 1 | 4.143 | 241387 | 26.7
3-way | 2 | 3.775 | 264872 | 29.3
3-way | 3 | 4.116 | 242929 | 26.9
FastCrc32c|1 | 4.037 | 247727 | 27.4
FastCrc32c|2 | 4.648 | 215166 | 23.8
FastCrc32c|3 | 4.352 | 229799 | 25.4
AVG
Algorithm | Average of micros/op | Average of ops/sec | Average of Throughput (MB/s)
3-way | 4.01 | 249,729 | 27.63
FastCrc32c | 4.35 | 230,897 | 25.53
2) Crc32c computation CPU cost (inclusive samples percentage)
PER RUN
Implementation | run | TotalSamples | Crc32c percentage
3-way  | 1  | 4,572,250,000 | 4.37%
3-way  | 2  | 3,779,250,000 | 4.62%
3-way  | 3  | 4,129,500,000 | 4.48%
FastCrc32c   | 1  | 4,663,500,000 | 11.24%
FastCrc32c   | 2  | 4,047,500,000 | 12.34%
FastCrc32c   | 3  | 4,366,750,000 | 11.68%
**# Test Plan**
make -j64 corruption_test && ./corruption_test
By default it uses 3-way SSE algorithm
NO_THREEWAY_CRC32C=1 make -j64 corruption_test && ./corruption_test
make clean && DEBUG_LEVEL=0 make -j64 db_bench
make clean && DEBUG_LEVEL=0 NO_THREEWAY_CRC32C=1 make -j64 db_bench
Closes https://github.com/facebook/rocksdb/pull/3173
Differential Revision: D6330882
Pulled By: yingsu00
fbshipit-source-id: 8ec3d89719533b63b536a736663ca6f0dd4482e9
Summary:
We dump blob db options on blob db open, but it was removed by mistake in #3246. Adding it back.
Closes https://github.com/facebook/rocksdb/pull/3298
Differential Revision: D6607177
Pulled By: yiwu-arbug
fbshipit-source-id: 2a4aacbfa52fd8f1878dc9e1fbb95fe48faf80c0
Summary:
Previously, if blob_db_options.bytes_per_sync, there is a background job to call fsync() for every bytes_per_sync bytes written to a blob file. With the change we simply pass bytes_per_sync as env_options_ to blob files so that sync_file_range() will be used instead.
Closes https://github.com/facebook/rocksdb/pull/3297
Differential Revision: D6606994
Pulled By: yiwu-arbug
fbshipit-source-id: 452424be52e32ba92f5ea603b564e9b88929af47
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:
Wrote the blog post.
Closes https://github.com/facebook/rocksdb/pull/3289
Differential Revision: D6599031
Pulled By: ajkr
fbshipit-source-id: 77ee553196f225f20c56112d2c015b6fa14f1b83
Summary:
The TSAN version of tests could take quite long. Make the buck tests parallel to avoid timeouts.
Closes https://github.com/facebook/rocksdb/pull/3280
Differential Revision: D6581594
Pulled By: maysamyabandeh
fbshipit-source-id: 3f8476d8c69f0183e394fa8a2089dd8d4e90c90c
Summary:
ScopedArenaIterator should be defined after range_del_agg so that it destructs the assigned iterator, which depends on range_del_agg, before it range_del_agg is already destructed.
Closes https://github.com/facebook/rocksdb/pull/3281
Differential Revision: D6592332
Pulled By: maysamyabandeh
fbshipit-source-id: 89a15d8ed13d0fc856b0c47dce3d91778738dbac
Summary:
* Include `unistd.h` for `sleep(3)`
* Include `sys/time.h` for `gettimeofday(3)`
* Include `utils/random.h` for `Random64`
Error messages:
utilities/persistent_cache/hash_table_bench.cc: In constructor ‘rocksdb::HashTableBenchmark::HashTableBenchmark(rocksdb::HashTableImpl<long unsigned int, std::__cxx11::basic_string<char> >*, size_t, size_t, size_t, size_t)’:
utilities/persistent_cache/hash_table_bench.cc:76:28: error: ‘sleep’ was not declared in this scope
/* sleep override */ sleep(1);
^~~~~
utilities/persistent_cache/hash_table_bench.cc:76:28: note: suggested alternative: ‘strsep’
/* sleep override */ sleep(1);
^~~~~
strsep
utilities/persistent_cache/hash_table_bench.cc: In member function ‘void rocksdb::HashTableBenchmark::RunRead()’:
utilities/persistent_cache/hash_table_bench.cc:107:5: error: ‘Random64’ was not declared in this scope
Random64 rgen(time(nullptr));
^~~~~~~~
utilities/persistent_cache/hash_table_bench.cc:107:5: note: suggested alternative: ‘random_r’
Random64 rgen(time(nullptr));
^~~~~~~~
random_r
utilities/persistent_cache/hash_table_bench.cc:110:18: error: ‘rgen’ was not declared in this scope
size_t k = rgen.Next() % max_prepop_key;
^~~~
utilities/persistent_cache/hash_table_bench.cc: In static member function ‘static uint64_t rocksdb::HashTableBenchmark::NowInMillSec()’:
utilities/persistent_cache/hash_table_bench.cc:153:5: error: ‘gettimeofday’ was not declared in this scope
gettimeofday(&tv, /*tz=*/nullptr);
^~~~~~~~~~~~
make[2]: *** [CMakeFiles/hash_table_bench.dir/build.make:63: CMakeFiles/hash_table_bench.dir/utilities/persistent_cache/hash_table_bench.cc.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:3346: CMakeFiles/hash_table_bench.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
Closes https://github.com/facebook/rocksdb/pull/3283
Differential Revision: D6594850
Pulled By: ajkr
fbshipit-source-id: fd83957338c210cdfd253763347aafd39476824f
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
Summary:
Add a new histogram stat called rocksdb.db.flush.micros for memtable
flush
Closes https://github.com/facebook/rocksdb/pull/3269
Differential Revision: D6559496
Pulled By: anand1976
fbshipit-source-id: f5c771ba2568630458751795e8c37a493ff9b14d
Summary:
We added a new verification that ensures a value that snapshot reads when is released is the same as when it was created. This test however fails when the cf is dropped in between. The patch skips the tests if that was the case.
Closes https://github.com/facebook/rocksdb/pull/3279
Differential Revision: D6581584
Pulled By: maysamyabandeh
fbshipit-source-id: afe37d371c0f91818d2e279b3949b810e112e8eb
Summary:
Previously we store sequence number range of each blob files, and use the sequence number range to check if the file can be possibly visible by a snapshot. But it adds complexity to the code, since the sequence number is only available after a write. (The current implementation get sequence number by calling GetLatestSequenceNumber(), which is wrong.) With the patch, we are not storing sequence number range, and check if snapshot_sequence < obsolete_sequence to decide if the file is visible by a snapshot (previously we check if first_sequence <= snapshot_sequence < obsolete_sequence).
Closes https://github.com/facebook/rocksdb/pull/3274
Differential Revision: D6571497
Pulled By: yiwu-arbug
fbshipit-source-id: ca06479dc1fcd8782f6525b62b7762cd47d61909
Summary:
- check most times after calling snprintf that the buffer didn't fill up. Previously we'd proceed and use `buf_size - len` as the length in subsequent calls, which underflowed as those are unsigned size_t.
- replace some memcpys with snprintf for consistency
Closes https://github.com/facebook/rocksdb/pull/3255
Differential Revision: D6541464
Pulled By: ajkr
fbshipit-source-id: 8610ea6a24f38e0a37c6d17bc65b7c712da6d932
Summary:
added `ThreadType::BOTTOM_PRIORITY` which is used in the `ThreadStatus` object to indicate the thread is used for bottom-pri compactions. Previously there was a bug where we mislabeled such threads as `ThreadType::LOW_PRIORITY`.
Closes https://github.com/facebook/rocksdb/pull/3270
Differential Revision: D6559428
Pulled By: ajkr
fbshipit-source-id: 96b1a50a9c19492b1a5fd1b77cf7061a6f9f1d1c
Summary:
There were a few places where MSVC's implicit truncation warnings were getting triggered, which was causing the MSVC build to fail due to warnings being treated as errors. This resolves the issues by making the truncations in some places explicit, and by making it so there are no truncations of literals.
Fixes#3239
Supersedes #3259
Closes https://github.com/facebook/rocksdb/pull/3273
Reviewed By: yiwu-arbug
Differential Revision: D6569204
Pulled By: Orvid
fbshipit-source-id: c188cf1cf98d9acb6d94b71875041cc81f8ff088
Summary:
NUMBER_BLOCK_DECOMPRESSED and NUMBER_BLOCK_COMPRESSED are not reported unless the stats level contain detailed timers, which is wrong. They are normal counters. Fix it.
Closes https://github.com/facebook/rocksdb/pull/3263
Differential Revision: D6552519
Pulled By: siying
fbshipit-source-id: 40899ccea7b2856bb39752616657c0bfd432f6f9
Summary:
Add "--use_txn" option to use transactional API in db_stress, default being WRITE_PREPARED policy, which is the main intention of modifying db_stress. It also extend the existing snapshots to verify that before releasing a snapshot a read from it returns the same value as before.
Closes https://github.com/facebook/rocksdb/pull/3243
Differential Revision: D6556912
Pulled By: maysamyabandeh
fbshipit-source-id: 1ae31465be362d44bd06e635e2e9e49a1da11268
Summary:
Currently WriteImplWALOnly simply returns when disableWAL is set. This is an incorrect behavior since it does not allocated the sequence number, which is a side-effect of writing to the WAL. This patch fixes the issue.
Closes https://github.com/facebook/rocksdb/pull/3262
Differential Revision: D6550974
Pulled By: maysamyabandeh
fbshipit-source-id: 745a83ae8f04e7ca6c8ffb247d6ef16c287c52e7
Summary:
DeleteScheduler::MarkAsTrash() don't handle existing .trash files correctly
This cause rocksdb to not being able to delete existing .trash files on restart
Closes https://github.com/facebook/rocksdb/pull/3261
Differential Revision: D6548003
Pulled By: IslamAbdelRahman
fbshipit-source-id: c3800639412e587a690062c63076a5a08881e0e6
Summary:
Some call sites of BlockFetcher create temporary ReadOptions and pass to BlockFetcher. The temporary object will be gone after BlockFetcher construction but BlockFetcher keep its reference, causing stack-use-after-scope. Fixing it.
Closes https://github.com/facebook/rocksdb/pull/3258
Differential Revision: D6547152
Pulled By: yiwu-arbug
fbshipit-source-id: 6b49e9dd46bb72307f5d8f88ea15faacff35b9bc
Summary:
Add snapshot_checker check whenever we need to check sequence against snapshots and decide what to do with an input key. The changes are related to one of:
* compaction filter
* single delete
* delete at bottom level
* merge
Closes https://github.com/facebook/rocksdb/pull/3251
Differential Revision: D6537850
Pulled By: yiwu-arbug
fbshipit-source-id: 3faba40ed5e37779f4a0cb7ae78af9546659c7f2
