Summary:
This fixes a compilation failure on Linux when the system libc is not
glibc. jemalloc's configure script incorrectly assumes that glibc is
always used on Linux systems, producing glibc-style signatures; when
the system libc is e.g. musl, the following error is observed:

```
  [  0%] Building CXX object CMakeFiles/rocksdb.dir/db/db_impl.cc.o
  In file included from /go/src/github.com/cockroachdb/cockroach/c-deps/rocksdb.src/table/block.h:19:0,
                   from /go/src/github.com/cockroachdb/cockroach/c-deps/rocksdb.src/db/db_impl.cc:77:
  /x-tools/x86_64-unknown-linux-musl/x86_64-unknown-linux-musl/sysroot/usr/include/malloc.h:19:8: error: declaration of 'size_t malloc_usable_size(void*)' has a different exception specifier
   size_t malloc_usable_size(void *);
          ^~~~~~~~~~~~~~~~~~
  In file included from /go/src/github.com/cockroachdb/cockroach/c-deps/rocksdb.src/db/db_impl.cc:20:0:
  /go/native/x86_64-unknown-linux-musl/jemalloc/include/jemalloc/jemalloc.h:78:33: note: from previous declaration 'size_t malloc_usable_size(void*) throw ()'
   #  define je_malloc_usable_size malloc_usable_size
                                   ^
  /go/native/x86_64-unknown-linux-musl/jemalloc/include/jemalloc/jemalloc.h:239:41: note: in expansion of macro 'je_malloc_usable_size'
   JEMALLOC_EXPORT size_t JEMALLOC_NOTHROW je_malloc_usable_size(
                                           ^~~~~~~~~~~~~~~~~~~~~
  CMakeFiles/rocksdb.dir/build.make:350: recipe for target 'CMakeFiles/rocksdb.dir/db/db_impl.cc.o' failed
```

This works around the issue by rearranging the sources such that
jemalloc's headers are never in the same scope as the system's malloc
header. The jemalloc issue has been reported as well, see:
https://github.com/jemalloc/jemalloc/issues/778.

cc tschottdorf
Closes https://github.com/facebook/rocksdb/pull/2188

Differential Revision: D5163048

Pulled By: siying

fbshipit-source-id: c553125458892def175c1be5682b0330d80b2a0d

Summary:
Blob db rely on base db returning sequence number through write batch after DB::Write(). However after recent changes to the write path, DB::Writ()e no longer return sequence number in some cases. Fixing it by have WriteBatchInternal::InsertInto() always encode sequence number into write batch.

Stacking on #2375.
Closes https://github.com/facebook/rocksdb/pull/2385

Differential Revision: D5148358

Pulled By: yiwu-arbug

fbshipit-source-id: 8bda0aa07b9334ed03ed381548b39d167dc20c33

Summary:
Re-enable blob_db_test with some update:
* Commented out delay at the end of GC tests. Will update the logic later with sync point to properly trigger GC.
* Added some helper functions.

Also update make files to include blob_dump tool.
Closes https://github.com/facebook/rocksdb/pull/2375

Differential Revision: D5133793

Pulled By: yiwu-arbug

fbshipit-source-id: 95470b26d0c1f9592ba4b7637e027fdd263f425c

Reviewed By: meyering

Differential Revision: D5094332

fbshipit-source-id: 3df2f693def8ca418bc9febe3e20ccf051f2e19d

Summary:
update targets file for release
Closes https://github.com/facebook/rocksdb/pull/2358

Differential Revision: D5115705

Pulled By: lightmark

fbshipit-source-id: 96a3c7e15b5807b5d0f5a9bb73850b92754b5794

Summary:
We've had a couple CockroachDB users fail to build RocksDB on exotic platforms, so I figured I'd try my hand at solving these issues upstream. The problems stem from a) `USE_SSE=1` being too aggressive about turning on SSE4.2, even on toolchains that don't support SSE4.2 and b) RocksDB attempting to detect support for thread-local storage based on OS, even though it can vary by compiler on the same OS.

See the individual commit messages for details. Regarding SSE support, this PR should change virtually nothing for non-CMake based builds. `make`, `PORTABLE=1 make`, `USE_SSE=1 make`, and `PORTABLE=1 USE_SSE=1 make` function exactly as before, except that SSE support will be automatically disabled when a simple SSE4.2-using test program fails to compile, as it does on OpenBSD. (OpenBSD's ports GCC supports SSE4.2, but its binutils do not, so `__SSE_4_2__` is defined but an SSE4.2-using program will fail to assemble.) A warning is emitted in this case. The CMake build is modified to support the same set of options, except that `USE_SSE` is spelled `FORCE_SSE42` because `USE_SSE` is rather useless now that we can automatically detect SSE support, and I figure changing options in the CMake build is less disruptive than changing the non-CMake build.

I've tested these changes on all the platforms I can get my hands on (macOS, Windows MSVC, Windows MinGW, and OpenBSD) and it all works splendidly. Let me know if there's anything you object to—I obviously don't mean to break any of your build pipelines in the process of fixing ours downstream.
Closes https://github.com/facebook/rocksdb/pull/2199

Differential Revision: D5054042

Pulled By: yiwu-arbug

fbshipit-source-id: 938e1fc665c049c02ae15698e1409155b8e72171

Summary:
snprintf is in <stdio.h> and not in namespace std.
Closes https://github.com/facebook/rocksdb/pull/2287

Reviewed By: anirbanr-fb

Differential Revision: D5054752

Pulled By: yiwu-arbug

fbshipit-source-id: 356807ec38f3c7d95951cdb41f31a3d3ae0714d4

Summary:
- Introduced an include/ file dedicated to db-related debug functions to avoid making db.h more complex
- Added debugging function, `GetAllKeyVersions()`, to return a listing of internal data for a range of user keys. The new `struct KeyVersion` exposes data similar to internal key without exposing any internal type.
- Migrated the "ldb idump" subcommand to use this function
- The API takes an inclusive-exclusive range to match behavior of "ldb idump". This will be quite annoying for users who want to query a single user key's versions :(.
Closes https://github.com/facebook/rocksdb/pull/2232

Differential Revision: D4976007

Pulled By: ajkr

fbshipit-source-id: cab375da53a7595d6575af2b7e3b776aa3ad793e

Summary:
address siying's comment in #2272.
Closes https://github.com/facebook/rocksdb/pull/2274

Differential Revision: D5039489

Pulled By: ajkr

fbshipit-source-id: 3e2d957d3469c13d0e33ededa59320c4c3f24ef6

Summary:
The final pull request for Blob Storage.
Closes https://github.com/facebook/rocksdb/pull/2269

Differential Revision: D5033189

Pulled By: yiwu-arbug

fbshipit-source-id: 6356b683ccd58cbf38a1dc55e2ea400feecd5d06

Summary:
- added a feature test in build_detect_platform to check whether sched_getcpu() is available. glibc offers it only on some platforms (e.g., linux but not mac); this way should be easier than maintaining a list of platforms on which it's available.
- refactored PhysicalCoreID() to be simpler / less repetitive. ordered the conditional compilation clauses from most-to-least preferred
Closes https://github.com/facebook/rocksdb/pull/2272

Differential Revision: D5038093

Pulled By: ajkr

fbshipit-source-id: 81d7db3cc620250de220bdeb3194b2b3d7673de7

Summary:
I'm going to add more DB tests for statistics as currently we have very few. I started a file dedicated to this purpose and moved the existing stats-specific tests there.
Closes https://github.com/facebook/rocksdb/pull/2211

Differential Revision: D4951558

Pulled By: ajkr

fbshipit-source-id: 05d11c35079c40ecabdfd2cf5556ccb761f694a4

Summary:
These code paths forked when checkpoint was introduced by copy/pasting the core backup logic. Over time they diverged and bug fixes were sometimes applied to one but not the other (like fix to include all relevant WALs for 2PC), or it required extra effort to fix both (like fix to forge CURRENT file). This diff reunites the code paths by extracting the core logic into a function, CreateCustomCheckpoint(), that is customizable via callbacks to implement both checkpoint and backup.

Related changes:

- flush_before_backup is now forcibly enabled when 2PC is enabled
- Extracted CheckpointImpl class definition into a header file. This is so the function, CreateCustomCheckpoint(), can be called by internal rocksdb code but not exposed to users.
- Implemented more functions in DummyDB/DummyLogFile (in backupable_db_test.cc) that are used by CreateCustomCheckpoint().
Closes https://github.com/facebook/rocksdb/pull/1932

Differential Revision: D4622986

Pulled By: ajkr

fbshipit-source-id: 157723884236ee3999a682673b64f7457a7a0d87

Summary:
Add buckifier script and TARGETS file to github repo
Closes https://github.com/facebook/rocksdb/pull/2083

Differential Revision: D4825822

Pulled By: IslamAbdelRahman

fbshipit-source-id: 205f4a7