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

Test Plan: TBD

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D56601

Cosmetic changes and comment update

Summary: In DBTest.HardLimit, multiple flushes may merge into one, based on thread scheduling. Avoid it by waiting each flush to finish before generating the next one.

Test Plan: Run test in parallel several times and see it doesn't fail any more.

Reviewers: yhchiang, kradhakrishnan, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: yiwu, leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D56853

Summary: DBTestUniversalCompaction, IncreaseUniversalCompactionNumLevels fails one in about 30 runs when running in parallel. We wait for compaction after each flush to make the compaction behavior deterministic.

Test Plan: Run the test 1000 times in parallel and it still passes.

Reviewers: yhchiang, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: kradhakrishnan, yiwu, leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D56841

Summary: It is useful to print out IO stats in flush jobs too. Extend options.compaction_measure_io_stats to flush jobs and raname it.

Test Plan: Try db_bench and see the stats are printed out.

Reviewers: yhchiang

Reviewed By: yhchiang

Subscribers: kradhakrishnan, yiwu, IslamAbdelRahman, leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D56769

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: The reason for this test flakiness is that we try to verify that number of files in L0 is 3 after flushing the 3rd file although we may have a compaction running in the background that may finish before we do the check and the 3 L0 files are converted to 1 L1 file

Test Plan: Run a modified version of the test that sleep before doing the check

Reviewers: sdong, andrewkr, kradhakrishnan, yhchiang

Reviewed By: yhchiang

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D56643

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:
In some case, it is possible to have two concesutive SST files might sharing
same boundary keys.  However, in the assertion in Compaction::ShouldStopBefore,
it exclude such possibility.

This patch fix this issue by relaxing the assertion to allow the equal case.

Test Plan: rocksdb tests

Reviewers: IslamAbdelRahman, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D55875

Summary: Fixed a bug in RocksDB Statistics where flush is considered as compaction

Test Plan: unit test

Reviewers: sdong, IslamAbdelRahman, rven, kradhakrishnan, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D56271

Summary: The code assumes that if use_mmap_reads is on then use_os_buffer is also on.  This make sense as by using memory mapped files for reading you are expecting the OS to cache what it needs.  Add code to make sure the user does not turn off use_os_buffer when they turn on use_mmap_reads

Test Plan: New test: DBTest.MMapAndBufferOptions

Reviewers: sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D56397

Summary:
Added the column family name to the properties block. This property
is omitted only if the property is unavailable, such as when RepairDB()
writes SST files.

In a next diff, I will change RepairDB to use this new property for
deciding to which column family an existing SST file belongs. If this
property is missing, it will add it to the "unknown" column family (same
as its existing behavior).

Test Plan:
New unit test:

  $ ./db_table_properties_test --gtest_filter=DBTablePropertiesTest.GetColumnFamilyNameProperty

Reviewers: IslamAbdelRahman, yhchiang, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D55605

Summary: We use object `v` in the error message, which is not initialized if the edit is column family manipulation. This doesn't provide much useful info, so this diff is removing it. Instead, it dumps actual VersionEdit contents.

Test Plan: compiles. would be great to get tests in version_set_test.cc that cover cases where a file write fails

Reviewers: sdong, yhchiang, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D56349

Summary:
There is a hardcoded constraint in our statistics collection that prevents reading properties from more than 20 SST files. This means our statistics will be very inaccurate for databases with > 20 files since additional files are just ignored. The purpose of constraining the number of files used is to bound the I/O performed during statistics collection, since these statistics need to be recomputed every time the database reopened.

However, this constraint doesn't take into account the case where option "max_open_files" is -1. In that case, all the file metadata has already been read, so MaybeInitializeFileMetaData() won't incur any I/O cost. so this diff gets rid of the 20-file constraint in case max_open_files == -1.

Test Plan:
write into unit test db/db_properties_test.cc - "ValidateSampleNumber".
We generate 20 files with 2 rows and 10 files with 1 row.
If max_open_files !=-1, the `rocksdb.estimate-num-keys` should be (10*1 + 10*2)/20 * 30 = 45. Otherwise, it should be the ground truth, 50.
{F1089153}

Reviewers: andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D56253

Summary:
This patch is similar to D52563, When we iterate over a DB with merge operands we keep creating std::queue to store the operands, optimize this by reusing merge_operands_ data member

Before the patch

```
./db_bench --benchmarks="mergerandom,readseq,readseq,readseq,readseq" --db="/dev/shm/bench_merge_memcpy_on_the_fly/" --merge_operator="put" --merge_keys=10000 --num=10000

DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
mergerandom  :       3.757 micros/op 266141 ops/sec;   29.4 MB/s ( updates:10000)
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.413 micros/op 2423538 ops/sec;  268.1 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.451 micros/op 2219071 ops/sec;  245.5 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.420 micros/op 2382039 ops/sec;  263.5 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.408 micros/op 2452017 ops/sec;  271.3 MB/s

DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
mergerandom  :       3.947 micros/op 253376 ops/sec;   28.0 MB/s ( updates:10000)
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.441 micros/op 2266473 ops/sec;  250.7 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.471 micros/op 2122033 ops/sec;  234.8 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.440 micros/op 2271407 ops/sec;  251.3 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.429 micros/op 2331471 ops/sec;  257.9 MB/s
```

with the patch

```
./db_bench --benchmarks="mergerandom,readseq,readseq,readseq,readseq" --db="/dev/shm/bench_merge_memcpy_on_the_fly/" --merge_operator="put" --merge_keys=10000 --num=10000

DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
mergerandom  :       4.080 micros/op 245092 ops/sec;   27.1 MB/s ( updates:10000)
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.308 micros/op 3241843 ops/sec;  358.6 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.312 micros/op 3200408 ops/sec;  354.0 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.332 micros/op 3013962 ops/sec;  333.4 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.300 micros/op 3328017 ops/sec;  368.2 MB/s

DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
mergerandom  :       3.973 micros/op 251705 ops/sec;   27.8 MB/s ( updates:10000)
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.320 micros/op 3123752 ops/sec;  345.6 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.335 micros/op 2986641 ops/sec;  330.4 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.339 micros/op 2950047 ops/sec;  326.4 MB/s
DB path: [/dev/shm/bench_merge_memcpy_on_the_fly/]
readseq      :       0.319 micros/op 3131565 ops/sec;  346.4 MB/s
```

Test Plan: make check -j64

Reviewers: yhchiang, andrewkr, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D56031

Summary:
  - Put key offset and key size in WriteBatchIndexEntry
  - Use vector for comparators in WriteBatchEntryComparator

I use a slightly modified version of @yoshinorim code to benchmark
https://gist.github.com/IslamAbdelRahman/b120f4fba8d6ff7d58d2

For Put I create a transaction that put a 1000000 keys and measure the time spent without commit.
For GetForUpdate I read the keys that I added in the Put transaction.

Original time:

```
 rm -rf /dev/shm/rocksdb-example/
 ./txn_bench put 1000000
 1000000 OK Ops | took      3.679 seconds
 ./txn_bench get_for_update 1000000
 1000000 OK Ops | took      3.940 seconds
```

New Time

```
  rm -rf /dev/shm/rocksdb-example/
 ./txn_bench put 1000000
 1000000 OK Ops | took      2.727 seconds
 ./txn_bench get_for_update 1000000
 1000000 OK Ops | took      3.880 seconds
```

It looks like there is no significant improvement in GetForUpdate() but we can see ~30% improvement in Put()

Test Plan: unittests

Reviewers: yhchiang, anthony, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba, yoshinorim

Differential Revision: https://reviews.facebook.net/D55539

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: Change some RocksDB default options to make it more friendly to server workloads.

Test Plan: Run all existing tests

Reviewers: yhchiang, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: sumeet, muthu, benj, MarkCallaghan, igor, leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55941

kHeader was moved from write_batch.cc to header file because
it is being used wherever the number "12" was being used to
check for record size

record.size() should not be less than 12.

This "magic number" seems to be the WriteBatch header (8 byte sequence
and 4 byte count).   Replaced all the places where "12" was used
by WriteBatchInternal::kHeader.

Summary: We were not measuring the time spent in merge_operator when called from Version::Get()

Test Plan: added a unittest

Reviewers: sdong, yhchiang

Reviewed By: yhchiang

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55905

Summary: Correct a typo in a comment

Test Plan: No code change.

Reviewers: sdong, kradhakrishnan, IslamAbdelRahman

Reviewed By: kradhakrishnan, IslamAbdelRahman

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D55803

Summary:
When subcompaction is used, all subcompactions share the same Compaction
pointer in CompactionJob while each subcompaction all keeps their mutable
stats in SubcompactionState.  However, there're still some mutable part
that is currently store in the shared Compaction pointer.

This patch makes two changes:

1. Make the shared Compaction pointer const so that it can never be modified
   during the compaction.
2. Move necessary states from Compaction to SubcompactionState.
3. Make functions of Compaction const if the function does not modify
   its internal state.

Test Plan: rocksdb and MyRocks test

Reviewers: sdong, kradhakrishnan, andrewkr, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: andrewkr, dhruba, yoshinorim, gunnarku, leveldb

Differential Revision: https://reviews.facebook.net/D55923

This reverts commit 522de4f5.

It has bug of index block cleaning up.

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:
Basic test cases:

- Manifest is lost or corrupt
- Manifest refers to too many or too few SST files
- SST file is corrupt
- Unflushed data is present when RepairDB is called

Depends on D55065 for its CreateFile() function in file_utils

Test Plan: Ran the tests.

Reviewers: IslamAbdelRahman, yhchiang, yoshinorim, sdong

Reviewed By: sdong

Subscribers: leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55485

Test Plan: make -j40 check OPT=-g, on both /tmp and /dev/shm

Reviewers: sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55701

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.
When the table reader is destroyed, it releases the pinned blocks (if there were any). This has to happen before the cache is destroyed, so I had to introduce a TableReader::Close(), to guarantee the order of destruction.

Test Plan:
Added two unit tests for this. Existing unit tests run fine (default is pin_l0_filter_and_index_blocks_in_cache=false).

DISABLE_JEMALLOC=1 OPT=-g make all valgrind_check -j32
  Mac: OK.
  Linux: with D55287 patched in it's OK.

Reviewers: sdong

Reviewed By: sdong

Subscribers: andrewkr, leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D54801

Summary:
DBBlockCacheTest.TestWithCompressedBlockCache is depending on compression using snappy, so this test fail when snappy is not available
block this test when we don't have snappy

https://ci-builds.fb.com/view/rocksdb/job/rocksdb_no_compression/833/console

Test Plan: run the test when compression libraries are not avaliable

Reviewers: sdong, yiwu

Reviewed By: yiwu

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55413

Summary:
The pre-existing code is trying to clamp between 65,536 and 0,
resulting in clamping to 65,536, resulting in very small buffers,
resulting in ShouldFlushNow() being true quite easily,
resulting in assertion failing and database performance
being "not what it should be".

https://github.com/facebook/rocksdb/issues/1018

Test Plan: make check

Reviewers: sdong, andrewkr, IslamAbdelRahman, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55455

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:
This patch bump the counters in the frequent code path DBIter::Next() / DBIter::Prev() in a local data members and send them to Statistics when the iterator is destroyed
A better solution will be to have thread_local implementation for Statistics

New performance
```
readseq      :       0.035 micros/op 28597881 ops/sec; 3163.7 MB/s
     1,851,568,819      stalled-cycles-frontend   #   31.29% frontend cycles idle    [49.86%]
       884,929,823      stalled-cycles-backend    #   14.95% backend  cycles idle    [50.21%]
readreverse  :       0.071 micros/op 14077393 ops/sec; 1557.3 MB/s
     3,239,575,993      stalled-cycles-frontend   #   27.36% frontend cycles idle    [49.96%]
     1,558,253,983      stalled-cycles-backend    #   13.16% backend  cycles idle    [50.14%]

```

Existing performance

```
readreverse  :       0.174 micros/op 5732342 ops/sec;  634.1 MB/s
    20,570,209,389      stalled-cycles-frontend   #   70.71% frontend cycles idle    [50.01%]
    18,422,816,837      stalled-cycles-backend    #   63.33% backend  cycles idle    [50.04%]

readseq      :       0.119 micros/op 8400537 ops/sec;  929.3 MB/s
    15,634,225,844      stalled-cycles-frontend   #   79.07% frontend cycles idle    [49.96%]
    14,227,427,453      stalled-cycles-backend    #   71.95% backend  cycles idle    [50.09%]
```

Test Plan: unit tests

Reviewers: yhchiang, sdong, igor

Reviewed By: sdong

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55107

fix: handle_fatal_signal (sig=6) in std::vector<std::string, std::allocator<std::string> >::_M_range_check | c++/4.8.2/bits/stl_vector.h:794 #174

Summary:
Fix for https://github.com/facebook/mysql-5.6/issues/174

When there is no old files to purge, vector.at(i) function was crashing

if (old_info_log_file_count != 0 &&
      old_info_log_file_count >= db_options_.keep_log_file_num) {
    std::sort(old_info_log_files.begin(), old_info_log_files.end());
    size_t end = old_info_log_file_count - db_options_.keep_log_file_num;
    for (unsigned int i = 0; i <= end; i++) {
      std::string& to_delete = old_info_log_files.at(i);

Added check to old_info_log_file_count be non zero.

Test Plan: run existing tests

Reviewers: gunnarku, vasilep, sdong, yhchiang

Reviewed By: yhchiang

Subscribers: andrewkr, webscalesql-eng, dhruba

Differential Revision: https://reviews.facebook.net/D55245