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

Latest versions of Jemalloc library do not require je_init()/je_unint()

  calls. #ifdef in the source code and make this a default build option.

Summary: For compactions benchmarks (both level and universal) we'll use `--max_write_buffer_number=4`. For all the other benchmarks which don't customize the value of `--max_background_flushes` we'll continue using `--max_write_buffer_number=8`.

Test Plan:
To validate basic correctness and command-line options:

```
cd ~/rocksdb
NKEYS=10000000 ./tools/run_flash_bench.sh
```

Reviewers: MarkCallaghan

Reviewed By: MarkCallaghan

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55497

Summary:
This fixes a similar issue as D54711: "CURRENT" file can mutate between
GetLiveFiles() and copy to the tmp directory, in which case it would reference
the wrong manifest filename. To fix this, I forge the "CURRENT" file such that
it simply contains the filename for the manifest returned by GetLiveFiles().

- Changed CreateCheckpoint() to forge current file
- Added CreateFile() utility function
- Added test case that rolls manifest during checkpoint creation

Test Plan:
  $ ./checkpoint_test

Reviewers: sdong, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D55065

Fixes warnings and ensure correct int behavior on 32-bit platforms.

Improve documentation of the allow_os_buffer parameter.

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

Fix FB internal CI build failure

Histogram Concurrency Improvement and Time-Windowing Support

Fix AppVeyor build error

Summary:
Using gcc 5.2.1 to compile RocksDB on Ubuntu 15.10 results in a warning about unused variable. Warning is treated as an error and all of it results in a build break. Fix the issue and make sure that everything compiles with that particular configuration.

P.S. Lint complains about a non-ASCII character used in the source code ("Wagner-Fischer"). Fix this as well.

Test Plan:
  # Everything compiler cleanly on the system which exhibited the problem.
  # `make clean && make -j 16` on CentOS.
  # `make clean && USE_CLANG=1 make -j 16` on CentOS.

Reviewers: sdong, igor

Reviewed By: igor

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55503

Summary: Set of updates to the subcompaction benchmark script which are based on our internal discussions. The intent behind the changes is to make sure that the scripts will correctly reflect how we're doing the actual benchmarking.

Test Plan: Tested by exercising the full set of compaction benchmarks and validating the execution and consistency of results.

Reviewers: MarkCallaghan, sdong, yhchiang

Reviewed By: yhchiang

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55461

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

Added quasardb to the USERS.md file

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: as titled

Test Plan: N/A

Reviewers: sdong, kradhakrishnan, anthony, yhchiang, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55323

Summary: This will make it easier for admins and devs to use RepairDB.

Test Plan:
Tried deleting the manifest and verified it recovers:

  $ ldb --create_if_missing --db=/tmp/test_db put ok ok
  $ rm -f /tmp/test_db/MANIFEST-000001
  $ ./ldb --db=/tmp/test_db repair
  $ ldb --db=/tmp/test_db get ok
  ok

Reviewers: yhchiang, sdong, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55359

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

Summary: Refactored db_bench transaction stress tests so that they can be called from unit tests as well.

Test Plan: run new unit test as well as db_bench

Reviewers: yhchiang, IslamAbdelRahman, sdong

Reviewed By: IslamAbdelRahman

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D55203

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

Summary:
- Keep track of obsolete manifests in VersionSet
- Updated FindObsoleteFiles() to put obsolete manifests in the JobContext for later use by PurgeObsoleteFiles()
- Added test case that verifies a stale manifest is deleted by a non-full purge

Test Plan:
  $ ./backupable_db_test --gtest_filter=BackupableDBTest.ChangeManifestDuringBackupCreation

Reviewers: IslamAbdelRahman, yoshinorim, sdong

Reviewed By: sdong

Subscribers: andrewkr, leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D55269

Summary:
Cache to have an option to fail Cache::Insert() when full. Update call sites to check status and handle error.

I totally have no idea what's correct behavior of all the call sites when they encounter error. Please let me know if you see something wrong or more unit test is needed.

Test Plan: make check -j32, see tests pass.

Reviewers: anthony, yhchiang, andrewkr, IslamAbdelRahman, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D54705

added --no_value option to ldb scan to dump key only

Summary:
This is a follow-up patch of https://reviews.facebook.net/D54891.
As the information about files being compacted will also be used
when making compaction decision, it is necessary to update the compaction
score when a compaction plan has been made but not yet execute.

This patch adds a missing call to update the compaction score in
CompactFiles().

Test Plan: compact_files_test

Reviewers: sdong, IslamAbdelRahman, kradhakrishnan, yiwu, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D55227

Summary:
ReleaseCompactionFiles must be called when DB mutex is held,
but the documentation is mission.

Test Plan: no code change

Reviewers: anthony, IslamAbdelRahman, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D54987

Summary: Extend optimization in D53835 to optimistic transactions for completeness.

Test Plan: added test

Reviewers: sdong, IslamAbdelRahman, horuff, jkedgar

Reviewed By: horuff

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D55059

Summary: Add db_test2 to .gitignore

Test Plan: make sure db_test2 dont show in "git status"

Reviewers: sdong, yhchiang, andrewkr, anthony

Reviewed By: anthony

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D55191

Summary: Previously, reusing a transaction (by passing it as an argument to BeginTransaction) would not clear the transaction's snapshot.  This is not a clear, well-definited behavior.

Test Plan: improved test

Reviewers: sdong, IslamAbdelRahman, horuff, jkedgar

Reviewed By: jkedgar

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D55053

Summary:
Update dependencies and fix broken clang symlink

version changes
```
zstd 0.4.7 => 0.5.1
jemalloc 4.0.3 => master
```

Test Plan:
make check -j64
USE_CLANG=1 make check -j64
ROCKSDB_FBCODE_BUILD_WITH_481=1 make check -j64

Reviewers: sdong, yhchiang, anthony, andrewkr

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D55179

Change Property name from "rocksdb.current_version_number" to "rocksdb.current-super-version-number"

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