Summary:
There is an undocumented behavior about a certain combination of options and operations.
- inplace_update_support = true, and
- call `SeekForPrev()`, `SeekToLast()`, and/or `Prev()` on unflushed data.

We should stop the backward iteration and report an error of `Status::NotSupported`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7618

Test Plan: make check

Reviewed By: pdillinger

Differential Revision: D24769619

Pulled By: riversand963

fbshipit-source-id: 81d199fa55ed4739ab10e719cc345a992238ccbb

Summary:
During seek, prefix compare should not include timestamp.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7644

Test Plan: added unittest

Reviewed By: riversand963

Differential Revision: D24772066

Pulled By: jay-zhuang

fbshipit-source-id: 3982655a8bf8da256a738e8497b73b3d9bdac92e

Summary:
The field in BlockBasedTableOptions is 4 bytes:
  // Default: 0 (disabled)
  uint32_t read_amp_bytes_per_bit = 0;

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7651

Reviewed By: ltamasi

Differential Revision: D24844994

Pulled By: riversand963

fbshipit-source-id: e2695e55532256ef8996dd6939cad06987a80293

Summary:
crash tests donot run in DEBUG_MODE=0 on tmpfs when
use_direct_reads/use_direct_io_for_flush_and_compaction is set randomly because
direct I/O is not supported on tmpfs and tests exit.

Fix: Sanitize direct I/O read options in DEBUG_LEVEL=0 so that crash
tests can run in tmpfs. When mmap_reads is set, direct I/O reads options are
unset so we can sanitize direct I/O reads options in case of tmpfs as well.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7643

Test Plan:
1. export DEBUG_LEVEL=0; export TEST_TMPDIR="/dev/shm";
           export CRASH_TEST_EXT_ARGS="--use_direct_reads=1 --mmap_read=0";
           make crash_test -j64
           2. In DEBUG_LEVEL=1 mode:  make crash_test -j64

Reviewed By: jay-zhuang

Differential Revision: D24766550

Pulled By: akankshamahajan15

fbshipit-source-id: 021720b2343c12c72004f84b26147625d3991d9e

Summary:
https://github.com/facebook/rocksdb/issues/7556 introduced support for compaction iterator to perform timestamp-aware garbage collection.
However, there was a bug. The comparison between `ikey_.user_key` and `current_user_key_` should happen
before `key_ = current_key_.SetInternalKey(key_, &ikey_);` (line 336 of compaction_iterator.cc).
Otherwise, after this line, `current_key_` is always the same as `ikey_.user_key`.

This PR also re-arranged the order of some data members because some of them are state variables of `CompactionIterator` while others are inputs from callers.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7645

Test Plan: make check

Reviewed By: ltamasi

Differential Revision: D24845028

Pulled By: riversand963

fbshipit-source-id: c7e79914832701462b86867e8463cd463b6c0c25

Summary:
After replaying the WALs, the memtables are flushed synchronously to L0 instead of being flushed in background. Currently, we only track WAL obsoletion events in the code path of background flush jobs. This PR tracks these events in RecoverLogFiles.

After this change, we can enable `track_and_verify_wal_in_manifest` in `db_stress`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7649

Test Plan: `python tools/db_crashtest.py whitebox`

Reviewed By: riversand963

Differential Revision: D24824501

Pulled By: cheng-chang

fbshipit-source-id: 207129f7b845c50b333680ce6818a68a2fad54b9

Summary:
Consider the following sequence of events:

1. Db flushed an SST with file number N, appended to MANIFEST, and tried to sync the MANIFEST.
2. Syncing MANIFEST failed and db crashed.
3. Db tried to recover with this MANIFEST. In the meantime, no entry about the newly-flushed SST was found in the MANIFEST. Therefore, RocksDB replayed WAL and tried to flush to an SST file reusing the same file number N. This failed because file system does not support overwrite. Then Db deleted this file.
4. Db crashed again.
5. Db tried to recover. When db read the MANIFEST, there was an entry referencing N.sst. This could happen probably because the append in step 1 finally reached the MANIFEST and became visible. Since N.sst had been deleted in step 3, recovery failed.

It is possible that N.sst created in step 1 is valid. Although step 3 would still fail since the MANIFEST was not synced properly in step 1 and 2, deleting N.sst would make it impossible for the db to recover even if the remaining part of MANIFEST was appended and visible after step 5.

After this PR, in step 3, immediately after recovering from MANIFEST, a new MANIFEST is created, then we find that N.sst is not referenced in the MANIFEST, so we delete it, and we'll not reuse N as file number. Then in step 5, since the new MANIFEST does not contain N.sst, the recovery failure situation in step 5 won't happen.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7621

Test Plan:
1. some tests are updated, because these tests assume that new MANIFEST is created after WAL recovery.
2. a new unit test is added in db_basic_test to simulate step 3.

Reviewed By: riversand963

Differential Revision: D24668144

Pulled By: cheng-chang

fbshipit-source-id: 90d7487fbad2bc3714f5ede46ea949895b15ae3b

Summary:
* Fully optimized StandardHasher, in terms of efficiently generating Start, CoeffRow, and ResultRow from a stock hash value, with sufficient independence between them to have no measurably degraded behavior. (Degraded behavior would be an FP rate higher than explainable by 2^-b and, if using a 32-bit stock hash function, expected stock hash collisions.) Details in code comments.
* Our standard 64-bit and 32-bit hash functions do not exhibit sufficient independence on sequential seeds (for one Ribbon construction attempt to have independent probability from the next). I have worked around this in the Ribbon code by "pre-mixing" "ordinal seeds," sequentially tried and appropriate for storage in persisted metadata, into "raw seeds," ready for application and appropriate for in-memory storage. This way the pre-mixing step (though fast) is only applied on loading or configuring the structure, not on each query or banding add.
* Fix a subtle flaw in which backtracking not clearing ResultRow data could lead to elevated FP rate on keys that were backtracked on and should (for generality) exhibit the same FP rate as novel keys.
* Added a basic test for PhsfQuery and construction algorithms (map or "retrieval structure" rather than set or filter), and made a few trivial related fixes.
* Better random configuration generation in unit tests
* Some other minor cleanup / clarification / etc.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7635

Test Plan: unit tests included

Reviewed By: jay-zhuang

Differential Revision: D24738978

Pulled By: pdillinger

fbshipit-source-id: f9d03599d9e2ca3e30e9d3e7d81cd936b56f76f0

Summary:
When a WAL is synced, an edit is written to MANIFEST.
After flushing memtables, the obsoleted WALs are piggybacked to MANIFEST while writing the new L0 files to MANIFEST.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7601

Test Plan:
`track_and_verify_wals_in_manifest` is enabled by default for all tests extending `DBBasicTest`, and in db_stress_test.
Unit test `wal_edit_test`, `version_edit_test`, and `version_set_test` are also updated.
Watch all tests to pass.

Reviewed By: ltamasi

Differential Revision: D24553957

Pulled By: cheng-chang

fbshipit-source-id: 66a569ff1bdced38e22900bd240b73113906e040

Summary:
The test often times out in internal test infra.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7640

Test Plan: watch test to pass internally

Reviewed By: anand1976

Differential Revision: D24764928

Pulled By: cheng-chang

fbshipit-source-id: 587f2afc97f52909837943fd938a86ca94544b2c

Summary:
In this test, after flushing memtable, it will read directly from the sst files, so `env_do_fsync` was `true` to ensure that the flushed sst files can be read afterwards. Considering that the test does not last long, the data should be available in os buffer even without fsync, so this PR tries to disable fsync to reduce test time.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7639

Test Plan: watch the test to pass in internal infra

Reviewed By: anand1976

Differential Revision: D24764689

Pulled By: cheng-chang

fbshipit-source-id: ef827611a3eaca04201e4280ae801d6c8e60c138

Summary:
The tests often times out in internal infra, skipping fsync should reduce test time.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7641

Test Plan: watch existing tests to pass

Reviewed By: anand1976

Differential Revision: D24765098

Pulled By: cheng-chang

fbshipit-source-id: c62bf8110361aee901918d632cf4772435d05e8d

Summary:
Tries to fix by skipping fsync.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7638

Test Plan: watch the tests to pass

Reviewed By: jay-zhuang

Differential Revision: D24764355

Pulled By: cheng-chang

fbshipit-source-id: 9c21b177709025ca1943066d94da89324ed47655

Summary:
This test often times out in internal test infra.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7637

Test Plan: watch test to pass

Reviewed By: ajkr

Differential Revision: D24763939

Pulled By: cheng-chang

fbshipit-source-id: 6564ee2ef637e9faf6688d4b6a5d74a72a51c5e8

Summary:
The original test nests a lot of `try` blocks. This PR flattens these blocks into independent blocks, so that each `try` block closes the DB before opening the next DB instance.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7608

Test Plan: watch the existing java tests to pass

Reviewed By: zhichao-cao

Differential Revision: D24611621

Pulled By: cheng-chang

fbshipit-source-id: d486c5d37ac25d4b860d739ef2cdd58e6064d42d

Summary:
`llvm-mirror/clang` is archived. Get the `clang-format-diff.py` file from the active source.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7609

Reviewed By: ajkr

Differential Revision: D24711608

Pulled By: pdillinger

fbshipit-source-id: b115d8765ff23fbb8190290a170de21565daba84

Summary:
In `BuildTable()`, we call `builder->Finish()` before evaluating `builder->NeedCompact()`.
However, we call `builder->NeedCompact()` before `builder->Finish()` in compaction job. This can be wrong because the table properties collectors may rely on the success of `Finish()` to provide correct result for `NeedCompact()`.

Test plan (on devserver):
make check

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7627

Reviewed By: ajkr

Differential Revision: D24728741

Pulled By: riversand963

fbshipit-source-id: 5a0dce244e14eb1106c4f87021e6bebca82b486e

Summary:
Existing API `VerifyChecksum()` allows application to verify sst files' block checksums.
Since whole file, user-specified checksum is tracked in MANIFEST, we can expose a new
API to verify sst files' file checksums.

```
// Compute table file checksums if applicable and compare with MANIFEST.
// Returns OK if no file has mismatching whole-file checksum.
Status DB::VerifyFileChecksums(const ReadOptions& /*read_options*/);
```

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7578

Test Plan: make check

Reviewed By: pdillinger

Differential Revision: D24436783

Pulled By: riversand963

fbshipit-source-id: 52b51519b842f2b3c4e3351998a97c86cbec85b3

Summary:
Add "max_write_buffer_size_to_maintain" to crash test

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7634

Test Plan: make crash_test -j64

Reviewed By: zhichao-cao

Differential Revision: D24710401

Pulled By: akankshamahajan15

fbshipit-source-id: 89e0412aaa56b2ef5a75603971b82f4b0b494ab7

Summary:
The core algorithms for InterleavedSolutionStorage and the
implementation SerializableInterleavedSolution make Ribbon fast for
filter queries. Example output from new unit test:

    Simple      outside query, hot, incl hashing, ns/key: 117.796
    Interleaved outside query, hot, incl hashing, ns/key: 42.2655
    Bloom       outside query, hot, incl hashing, ns/key: 24.0071

Also includes misc cleanup of previous Ribbon code and comments.

Some TODOs and FIXMEs remain for futher work / investigation.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7598

Test Plan: unit tests included (integration work and tests coming later)

Reviewed By: jay-zhuang

Differential Revision: D24559209

Pulled By: pdillinger

fbshipit-source-id: fea483cd354ba782aea3e806f2bc96e183d59441

Summary:
Recent test report shows that some tests have been skipped.

For DBWALTest that inherits from DBTestBase, the following will always be
true, since `env_` is an instance of `SpecialEnv`, not `Env::Default()`. Thus the test
will always be skipped.

```
if (options.env != Env::Default()) {
  ROCKSDB_GTEST_SKIP("Test requires default environment");
  return;
}
```

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7628

Test Plan:
./db_wal_test --gtest_filter=DBWALTest.TruncateLastLogAfterRecoverWithoutFlush
MEM_ENV=1 ./db_wal_test --gtest_filter=DBWALTest.TruncateLastLogAfterRecoverWithoutFlush
make check

Reviewed By: jay-zhuang

Differential Revision: D24693006

Pulled By: riversand963

fbshipit-source-id: 7f2a772492a0f11bff17bbf5e9f493e9e9a1c125

Summary:
The filter query key should not contain timestamp. The timestamp is
stripped for Get(), but not MultiGet().

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7589

Reviewed By: riversand963

Differential Revision: D24494661

Pulled By: jay-zhuang

fbshipit-source-id: fc5ff40f9d683a89a760c6ff0ab3aed05a70c317

Summary:
Test report shows that this test has been skipped recently due to
a condition that will never meet. `env_` is not equal to
`Env::Default()` for DBTest2 that inherits from DBTestBase.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7629

Test Plan:
make check
./db_test2 --gtest_filter=DBTest2.PinnableSliceAndMmapReads

Reviewed By: jay-zhuang

Differential Revision: D24693317

Pulled By: riversand963

fbshipit-source-id: b1bbd5c1e05a6fa57c1de0d74462b69e3c2d5215

Summary:
In dictionary compression's initial implementation, in order to save CPU overhead, we only enabled it
for bottom level under the assumption that the vast majority of data is
stored there. At that time, there was no
such thing as `ColumnFamilyOptions::bottommost_compression_opts`, so we just
hardcoded disabling dictionary compression in flush and compactions to
non-bottommost level. Now, we have users who generate all their files
through flush and are considering using dictionary compression.

To support such a use case, this PR expands the scope of `ColumnFamilyOptions::compression_opts` to
additionally include flushed files and files generated by compaction to
a non-bottommost level. Users can still get the old behavior by moving
their dictionary settings to `ColumnFamilyOptions::bottommost_compression_opts`
and explicitly enabling both that and `ColumnFamilyOptions::bottommost_compression`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7619

Reviewed By: ltamasi

Differential Revision: D24665610

Pulled By: ajkr

fbshipit-source-id: 656b90bce1033fe21c71e09af931ef5bde3e464c

Summary:
The recently reverted behavior changes were released to at least one
place internally, so we should mention the reverts in release notes.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7617

Reviewed By: akankshamahajan15

Differential Revision: D24654343

Pulled By: ajkr

fbshipit-source-id: eb64b2797d8508cd95a2dc2698122c1be29ce817

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/7615

Reviewed By: riversand963

Differential Revision: D24637054

Pulled By: ajkr

fbshipit-source-id: 7da20d44289eaa2387af4edf8c3c48057425cc1c

Summary:
Add 6.14 to check_format_compatible.sh

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7613

Test Plan: ./tools/check_format_compatible.sh

Reviewed By: riversand963

Differential Revision: D24628535

Pulled By: akankshamahajan15

fbshipit-source-id: a8bf1d5505a1fcc8a5bedc5ff4fdf33a22c3f2e6

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/7612

Reviewed By: zhichao-cao

Differential Revision: D24627054

Pulled By: riversand963

fbshipit-source-id: 451b4da742e3e84c7442bc7cc4959d39089b89d0

Summary:
This is a PR generated **semi-automatically** by an internal tool to remove unused includes and `using` statements.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7604

Test Plan: make check

Reviewed By: ajkr

Differential Revision: D24579392

Pulled By: riversand963

fbshipit-source-id: c4bfa6c6b08da1de186690d37eb73d8fff45aecd

Summary:
update GetColumnFamilyMetaData() to getColumnFamilyMetaData()

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7606

Reviewed By: zhichao-cao

Differential Revision: D24610298

Pulled By: cheng-chang

fbshipit-source-id: d24f9b65478da1456f50747637dc95688af874de

Summary:
CreateFileChecksumGenerator may uses requested_checksum_func_name in generator context to decide which generator will be used. GenerateOneFileChecksum has not being updated to use it, which will always get the generator when the name is empty. Fix it.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7586

Test Plan: make check

Reviewed By: riversand963

Differential Revision: D24491989

Pulled By: zhichao-cao

fbshipit-source-id: d9fdfdd431240f0a9a2e781ddbd48a7d6c609aad

Summary:
Fix a few typos and avoid a potential nullptr dereference.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7592

Reviewed By: zhichao-cao

Differential Revision: D24582111

Pulled By: riversand963

fbshipit-source-id: 51e9260e8cad1fcdedd310c889f0faeec6efd937

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/7593

Reviewed By: zhichao-cao

Differential Revision: D24576218

Pulled By: riversand963

fbshipit-source-id: a3d77191362ca696ae9df643f97f4ab5b7ecff12

Summary:
Because `Close()` have called in `Destroy()`

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7594

Reviewed By: zhichao-cao

Differential Revision: D24576407

Pulled By: riversand963

fbshipit-source-id: eba70d73375fd47dd78ca64c6a1fab3628448276

Summary:
Fixes Issue https://github.com/facebook/rocksdb/issues/7497

When allow_data_in_errors db_options is set, log error key details in `ParseInternalKey()`

Have fixed most of the calls. Have few TODOs still pending - because have to make more deeper changes to pass in the allow_data_in_errors flag. Will do those in a separate PR later.

Tests:
- make check
- some of the existing tests that exercise the "internal key too small" condition are: dbformat_test, cuckoo_table_builder_test
- some of the existing tests that exercise the corrupted key path are: corruption_test, merge_helper_test, compaction_iterator_test

Example of new status returns:
- Key too small - `Corrupted Key: Internal Key too small. Size=5`
- Corrupt key with allow_data_in_errors option set to false: `Corrupted Key: '<redacted>' seq:3, type:3`
- Corrupt key with allow_data_in_errors option set to true: `Corrupted Key: '61' seq:3, type:3`

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7515

Reviewed By: ajkr

Differential Revision: D24240264

Pulled By: ramvadiv

fbshipit-source-id: bc48f5d4475ac19d7713e16df37505b31aac42e7

Summary:
A user who extended `Logger` recently pointed out it is unusual to
require they implement the two-argument `Logv()` overload when they've
already implemented the three-argument `Logv()` overload. I agree with
that and think we can fix it by only calling the two-argument overload
from the default implementation of the three-argument overload. Then
when the three-argument overload is overridden, RocksDB would not
rely on the two-argument overload. Only `Logger::LogHeader()` needed
adjustment to achieve this.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7605

Reviewed By: riversand963

Differential Revision: D24584749

Pulled By: ajkr

fbshipit-source-id: 9aabe040ac761c4c0dbebc4be046967403ecaf21

Summary:
My previous change to use lib2to3 to migrate clang-format-diff.py
for Python 2 only works if there's nothing to reformat. Instead, give
instructions to download to REPO_ROOT.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7603

Test Plan: Try the instructions on a fresh CentOS 8 devserver

Reviewed By: riversand963

Differential Revision: D24569608

Pulled By: pdillinger

fbshipit-source-id: 1410ba163e016b226e883dec93fae3df9ed0eab2

Summary:
This PR does a few things:

1.  The MockFileSystem class was split out from the MockEnv.  This change would theoretically allow a MockFileSystem to be used by other Environments as well (if we created a means of constructing one).  The MockFileSystem implements a FileSystem in its entirety and does not rely on any Wrapper implementation.

2.  Make the RocksDB test suite work when MOCK_ENV=1 and ENCRYPTED_ENV=1 are set.  To accomplish this, a few things were needed:
- The tests that tried to use the "wrong" environment (Env::Default() instead of env_) were updated
- The MockFileSystem was changed to support the features it was missing or mishandled (such as recursively deleting files in a directory or supporting renaming of a directory).

3.  Updated the test framework to have a ROCKSDB_GTEST_SKIP macro.  This can be used to flag tests that are skipped.  Currently, this defaults to doing nothing (marks the test as SUCCESS) but will mark the tests as SKIPPED when RocksDB is upgraded to a version of gtest that supports this (gtest-1.10).

I have run a full "make check" with MEM_ENV, ENCRYPTED_ENV,  both, and neither under both MacOS and RedHat.  A few tests were disabled/skipped for the MEM/ENCRYPTED cases.  The error_handler_fs_test fails/hangs for MEM_ENV (presumably a timing problem) and I will introduce another PR/issue to track that problem.  (I will also push a change to disable those tests soon).  There is one more test in DBTest2 that also fails which I need to investigate or skip before this PR is merged.

Theoretically, this PR should also allow the test suite to run against an Env loaded from the registry, though I do not have one to try it with currently.

Finally, once this is accepted, it would be nice if there was a CircleCI job to run these tests on a checkin so this effort does not become stale.  I do not know how to do that, so if someone could write that job, it would be appreciated :)

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7566

Reviewed By: zhichao-cao

Differential Revision: D24408980

Pulled By: jay-zhuang

fbshipit-source-id: 911b1554a4d0da06fd51feca0c090a4abdcb4a5f

Summary:
Currently, the following interleaving of events can lead to SuperVersion containing both immutable memtables as well as the resulting L0. This can cause Get to return incorrect result if there are merge operands. This may also affect other operations such as single deletes.

```
  time  main_thr  bg_flush_thr  bg_compact_thr  compact_thr  set_opts_thr
0  |                                                         WriteManifest:0
1  |                                           issue compact
2  |                                 wait
3  |   Merge(counter)
4  |   issue flush
5  |                   wait
6  |                                                         WriteManifest:1
7  |                                 wake up
8  |                                 write manifest
9  |                  wake up
10 |  Get(counter)
11 |                  remove imm
   V
```

The reason behind is that: one bg flush thread's installing new `Version` can be batched and performed by another thread that is the "leader" MANIFEST writer. This bg thread removes the memtables from current super version only after `LogAndApply` returns. After the leader MANIFEST writer signals (releasing mutex) this bg flush thread, it is possible that another thread sees this cf with both memtables (whose data have been flushed to the newest L0) and the L0 before this bg flush thread removes the memtables.

To address this issue, each bg flush thread can pass a callback function to `LogAndApply`. The callback is responsible for removing the memtables. Therefore, the leader MANIFEST writer can call this callback and remove the memtables before releasing the mutex.

Test plan (devserver)
```
$make merge_test
$./merge_test --gtest_filter=MergeTest.MergeWithCompactionAndFlush
$make check
```

Pull Request resolved: https://github.com/facebook/rocksdb/pull/6069

Reviewed By: cheng-chang

Differential Revision: D18790894

Pulled By: riversand963

fbshipit-source-id: e41bd600c0448b4f4b2deb3f7677f95e3076b4ed

Summary:
Similarly to how https://github.com/facebook/rocksdb/issues/7345
integrated blob file writing into the flush process,
the patch adds support for writing blob files to the compaction logic.
Namely, if `enable_blob_files` is set, large values encountered during
compaction are extracted to blob files and replaced with blob indexes.
The resulting blob files are then logged to the MANIFEST as part of the
compaction job's `VersionEdit` and added to the `Version` alongside any
table files written by the compaction. Any errors during blob file building fail
the compaction job.

There will be a separate follow-up patch to perform blob garbage collection
during compactions.

In addition, the patch continues to chip away at the mess around computing
various compaction related statistics by eliminating some code duplication
and by making the `num_output_files` and `bytes_written` stats more consistent
for flushes, compactions, and recovery.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7573

Test Plan: `make check`

Reviewed By: riversand963

Differential Revision: D24404696

Pulled By: ltamasi

fbshipit-source-id: 21216af3a172ad3ce8f85d11cd30923784ae426c