Summary:
This patch completes the second part of the task: "Add blob support to the dump and dump_live_files command"
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9896
Reviewed By: ltamasi
Differential Revision: D35852667
Pulled By: jowlyzhang
fbshipit-source-id: a006456c881f468a92da689e895134762e9574e1
Summary:
This patch is the first part of adding blob dump support. It only adds blob dump support to the dump command. A follow up patch will add blob dump support to the dump_live_files command.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9881
Reviewed By: ltamasi
Differential Revision: D35796731
Pulled By: jowlyzhang
fbshipit-source-id: 2cc5973b222d505a331ac7b969edcf992b47c5ee
Summary:
This PR does not affect write-committed.
Add a member, `rollback_deletion_type_callback` to TransactionDBOptions
so that a write-prepared transaction, when rolling back, can call this
callback to decide if a `Delete` or `SingleDelete` should be used to
cancel a prior `Put` written to the database during prepare phase.
The purpose of this PR is to prevent mixing `Delete` and `SingleDelete`
for the same key, causing undefined behaviors. Without this PR, the
following can happen:
```
// The application always issues SingleDelete when deleting keys.
txn1->Put('a');
txn1->Prepare(); // writes to memtable and potentially gets flushed/compacted to Lmax
txn1->Rollback(); // inserts DELETE('a')
txn2->Put('a');
txn2->Commit(); // writes to memtable and potentially gets flushed/compacted
```
In the database, we may have
```
L0: [PUT('a', s=100)]
L1: [DELETE('a', s=90)]
Lmax: [PUT('a', s=0)]
```
If a compaction compacts L0 and L1, then we have
```
L1: [PUT('a', s=100)]
Lmax: [PUT('a', s=0)]
```
If a future transaction issues a SingleDelete, we have
```
L0: [SD('a', s=110)]
L1: [PUT('a', s=100)]
Lmax: [PUT('a', s=0)]
```
Then, a compaction including L0, L1 and Lmax leads to
```
Lmax: [PUT('a', s=0)]
```
which is incorrect.
Similar bugs reported and addressed in
https://github.com/cockroachdb/pebble/issues/1255. Based on our team's
current priority, we have decided to take this approach for now. We may
come back and revisit in the future.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9873
Test Plan: make check
Reviewed By: ltamasi
Differential Revision: D35762170
Pulled By: riversand963
fbshipit-source-id: b28d56eefc786b53c9844b9ef4a7807acdd82c8d
Summary:
... by filling out remaining testing hole: handling of
db_pathsi+cf_paths. (Note that while GetLiveFilesStorageInfo works
with db_paths / cf_paths, Checkpoint and BackupEngine do not and
are marked appropriately.)
Also improved comments for "live files" APIs, and grouped them
together in db.h.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9868
Test Plan: Adding to existing unit tests
Reviewed By: jay-zhuang
Differential Revision: D35752254
Pulled By: pdillinger
fbshipit-source-id: c70eb67748fad61826e2f554b674638700abefb2
Summary:
This patch completes the first part of the task: "Extend all three commands so they can decode and print blob references if a new option --decode_blob_index is specified"
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9870
Reviewed By: ltamasi
Differential Revision: D35753932
Pulled By: jowlyzhang
fbshipit-source-id: 9d2bbba0eef2ed86b982767eba9de1b4881f35c9
Summary:
We don't really have a mechanism for internal-only release
notes, so adding this to the standard release notes. For picking into
7.2 release.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9872
Test Plan: release note only
Reviewed By: jay-zhuang
Differential Revision: D35761307
Pulled By: pdillinger
fbshipit-source-id: 5d1932767fff48456323df948604dbb956ac27b2
Summary:
This allows to set with true the field `strict_capacity_limit` from C
API and other languages that wrap that.
Signed-off-by: Federico Guerinoni <guerinoni.federico@gmail.com>
Closes: https://github.com/facebook/rocksdb/issues/9707
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9855
Reviewed By: ajkr
Differential Revision: D35724150
Pulled By: jay-zhuang
fbshipit-source-id: d8514797e9d90b1cd88329018f9ac4776722aa0f
Summary:
`InitializeOptionsGeneral()` was overwriting many options that were already configured by OPTIONS file, potentially with the flag default values. This PR changes that function to only overwrite options in limited scenarios, as described at the top of its definition. Block cache is still a violation.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9862
Test Plan: ran under various scenarios (multi-DB, single DB, OPTIONS file, flags) and verified options are set as expected
Reviewed By: jay-zhuang
Differential Revision: D35736960
Pulled By: ajkr
fbshipit-source-id: 75b77740af37e6f5741618f8a8f5685df2417d03
Summary:
* Add valgrind test to nightly CircleCI (in case it can catch something that
ASAN/UBSAN does not)
* Add clang13+asan+ubsan+folly test to nightly CircleCI, for broader testing
* Consolidate many copies of ASAN_OPTIONS= while also allowing it to be
inherited from parent environment rather than always overridden.
* Move UBSAN exclusion from Makefile into options_settable_test.cc
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9859
Test Plan: CI
Reviewed By: jay-zhuang
Differential Revision: D35730903
Pulled By: pdillinger
fbshipit-source-id: 6f5464034e8115f9a07f6f7aec1de9219ec2837c
Summary:
Context:
As mentioned in https://github.com/facebook/rocksdb/issues/9701, we have the following in LITE=1 make static_lib for v7.0.2
```
CC file/sequence_file_reader.o
CC file/sst_file_manager_impl.o
CC file/writable_file_writer.o
In file included from file/writable_file_writer.cc:10:
./file/writable_file_writer.h:163:15: error: private field 'temperature_' is not used [-Werror,-Wunused-private-field]
Temperature temperature_;
^
1 error generated.
make: *** [file/writable_file_writer.o] Error 1
```
as titled
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9854
Test Plan:
- Local `LITE=1 make static_lib` reveals the same error and error is gone after this fix
- CI
Reviewed By: ajkr, jay-zhuang
Differential Revision: D35706585
Pulled By: hx235
fbshipit-source-id: 7743310298231ad6866304ffa2225c8abdc91d9a
Summary:
Since they operate at distinct abstraction layers, I thought it
was prudent to combine with EncryptedEnv CI test for each PR, for efficiency
in testing. Also added supported compressions to sst_dump --help output
so that CI job can verify no compiled-in compression support.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9850
Test Plan: CI, some manual stuff
Reviewed By: riversand963
Differential Revision: D35682346
Pulled By: pdillinger
fbshipit-source-id: be9879c1533fed304ee32c89fd9ba4b07c2b90cc
Summary:
Add a merge operator that allows users to register specific aggregation function so that they can does aggregation based per key using different aggregation types.
See comments of function CreateAggMergeOperator() for actual usage.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9780
Test Plan: Add a unit test to coverage various cases.
Reviewed By: ltamasi
Differential Revision: D35267444
fbshipit-source-id: 5b02f31c4f3e17e96dd4025cdc49fca8c2868628
Summary:
In `FileMetaData`, we keep track of the lowest-numbered blob file
referenced by the SST file in question for the purposes of BlobDB's
garbage collection in the `oldest_blob_file_number` field, which is
updated in `UpdateBoundaries`. However, with the current code,
`BlobIndex` decoding errors (or invalid blob file numbers) are swallowed
in this method. The patch changes this by propagating these errors
and failing the corresponding flush/compaction. (Note that since blob
references are generated by the BlobDB code and also parsed by
`CompactionIterator`, in reality this can only happen in the case of
memory corruption.)
This change necessitated updating some unit tests that involved
fake/corrupt `BlobIndex` objects. Some of these just used a dummy string like
`"blob_index"` as a placeholder; these were replaced with real `BlobIndex`es.
Some were relying on the earlier behavior to simulate corruption; these
were replaced with `SyncPoint`-based test code that corrupts a valid
blob reference at read time.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9851
Test Plan: `make check`
Reviewed By: riversand963
Differential Revision: D35683671
Pulled By: ltamasi
fbshipit-source-id: f7387af9945c48e4d5c4cd864f1ba425c7ad51f6
Summary:
This new options allows application to specify that files must be
ingested to bottommost level, otherwise the ingestion will fail instead
of silently ingesting to a non-bottommost level.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9849
Test Plan: make check
Reviewed By: ajkr
Differential Revision: D35680307
Pulled By: riversand963
fbshipit-source-id: 01cf54ef6c76198f7654dc06b5544631dea1be1e
Summary:
It's to support Meta's internal environment platform010. Gcc still doesn't work but USE_CLANG=1 should work.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9843
Test Plan: Try to make and ROCKSDB_FBCODE_BUILD_WITH_PLATFORM010=1 USE_CLANG=1 make
Reviewed By: pdillinger
Differential Revision: D35652507
fbshipit-source-id: a4a14b2fa4a2d6ca6fbf1b65060e81c39f079363
Summary:
The P95 and P99 metrics are flaky, similar to DBGet ones which removed
in https://github.com/facebook/rocksdb/issues/9742 .
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9844
Test Plan: `$ ./buckifier/buckify_rocksdb.py`
Reviewed By: ajkr
Differential Revision: D35655531
Pulled By: jay-zhuang
fbshipit-source-id: c1409f0fba4e23d461a65f988c27ac5e2ae85d13
Summary:
This change only add decode blob index support to dump_live_files command, which is part of a task to add blob support to a few commands.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9842
Reviewed By: ltamasi
Differential Revision: D35650167
Pulled By: jowlyzhang
fbshipit-source-id: a78151b98bc38ac6f52c6e01ca6927a3429ddd14
Summary:
Make `DB::GetUpdatesSince` return early if told to scan WALs generated by transactions
with write-prepared or write-unprepared policies (`seq_per_batch` is true), as indicated by
API comment.
Also add checks to `TransactionLogIterator` to clarify some conditions.
No API change.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9459
Test Plan:
make check
Closing https://github.com/facebook/rocksdb/issues/1565
Reviewed By: akankshamahajan15
Differential Revision: D33821243
Pulled By: riversand963
fbshipit-source-id: c8b155d020ce0980e2d3b3b1da40b96e65b48d79
Summary:
**This PR does not affect the functionality of `DB` and write-committed transactions.**
`CompactionIterator` uses `KeyCommitted(seq)` to determine if a key in the database is committed.
As the name 'write-committed' implies, if write-committed policy is used, a key exists in the database only if
it is committed. In fact, the implementation of `KeyCommitted()` is as follows:
```
inline bool KeyCommitted(SequenceNumber seq) {
// For non-txn-db and write-committed, snapshot_checker_ is always nullptr.
return snapshot_checker_ == nullptr ||
snapshot_checker_->CheckInSnapshot(seq, kMaxSequence) == SnapshotCheckerResult::kInSnapshot;
}
```
With that being said, we focus on write-prepared/write-unprepared transactions.
A few notes:
- A key can exist in the db even if it's uncommitted. Therefore, we rely on `snapshot_checker_` to determine data visibility. We also require that all writes go through transaction API instead of the raw `WriteBatch` + `Write`, thus at most one uncommitted version of one user key can exist in the database.
- `CompactionIterator` outputs a key as long as the key is uncommitted.
Due to the above reasons, it is possible that `CompactionIterator` decides to output an uncommitted key without
doing further checks on the key (`NextFromInput()`). By the time the key is being prepared for output, the key becomes
committed because the `snapshot_checker_(seq, kMaxSequence)` becomes true in the implementation of `KeyCommitted()`.
Then `CompactionIterator` will try to zero its sequence number and hit assertion error if the key is a tombstone.
To fix this issue, we should make the `CompactionIterator` see a consistent view of the input keys. Note that
for write-prepared/write-unprepared, the background flush/compaction jobs already take a "job snapshot" before starting
processing keys. The job snapshot is released only after the entire flush/compaction finishes. We can use this snapshot
to determine whether a key is committed or not with minor change to `KeyCommitted()`.
```
inline bool KeyCommitted(SequenceNumber sequence) {
// For non-txn-db and write-committed, snapshot_checker_ is always nullptr.
return snapshot_checker_ == nullptr ||
snapshot_checker_->CheckInSnapshot(sequence, job_snapshot_) ==
SnapshotCheckerResult::kInSnapshot;
}
```
As a result, whether a key is committed or not will remain a constant throughout compaction, causing no trouble
for `CompactionIterator`s assertions.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9830
Test Plan: make check
Reviewed By: ltamasi
Differential Revision: D35561162
Pulled By: riversand963
fbshipit-source-id: 0e00d200c195240341cfe6d34cbc86798b315b9f
Summary:
The minimum libzstd version that has `ZSTD_compressStream2` is
1.4.0 so only define ZSTD_STREAMING in that case.
Fixes building on Ubuntu 18.04 which has libzstd 1.3.3 as its
repository version.
Fixes https://github.com/facebook/rocksdb/issues/9795
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9841
Test Plan:
Build and test on Ubuntu 18.04 with:
apt-get install libsnappy-dev zlib1g-dev libbz2-dev liblz4-dev \
libzstd-dev libgflags-dev g++ make curl
Reviewed By: ajkr
Differential Revision: D35648738
Pulled By: jay-zhuang
fbshipit-source-id: 2a9e969bcc17a7dc10172f3817283409de885811
Summary:
This gives users the ability to examine the map populated by `GetMapProperty()` with property `kBlockCacheEntryStats`. It also sets us up for a possible future where cache reservations are configured according to `CacheEntryRole`s rather than flags coupled to roles.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9838
Test Plan:
- migrated test DBBlockCacheTest.CacheEntryRoleStats to use this API. That test verifies some of the contents are as expected
- added a DBPropertiesTest to verify the public map keys are present, and nothing else
Reviewed By: hx235
Differential Revision: D35629493
Pulled By: ajkr
fbshipit-source-id: 5c4356b8560e85d1f881fd32c44c15960b02fc68
Summary:
This information has been already available as part of the `rocksdb.blob-stats`
string property. The patch adds a dedicated integer property to make it easier
to surface this information in monitoring systems.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9835
Test Plan: `make check`
Reviewed By: riversand963
Differential Revision: D35619495
Pulled By: ltamasi
fbshipit-source-id: 03fb0b228aa27d3859a1e3783bcb7eca095607f8
Summary:
Add the ability to cancel remote compaction on the remote side by
setting `OpenAndCompactOptions.canceled` to true.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9725
Test Plan: added unittest
Reviewed By: ajkr
Differential Revision: D35018800
Pulled By: jay-zhuang
fbshipit-source-id: be3652f9645e0347df429e42a5614d5a9b3a1ec4
Summary:
We only run CI for VS2017 and VS2019 now, so the claim that users can build with "VS13" is stale.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9823
Reviewed By: riversand963
Differential Revision: D35511401
fbshipit-source-id: e3ae2643e26ab46753fea439599d2ed98abba439
Summary:
Henceforth, the version number in version.h shall reflect the
*next* version number to be tagged (to the best of our knowledge) rather
than the *previous* (unpatched) version.
The primary advantage is being able to distinguish (in source code `#if`s
or human running tools) the development version from the last released
version.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9834
Test Plan: CI
Reviewed By: ajkr
Differential Revision: D35617373
Pulled By: pdillinger
fbshipit-source-id: f3286089d17b82409e6af08e5aa9c1affefe2862
Summary:
Especially after updating to C++17, I don't see a compelling case for
*requiring* any folly components in RocksDB. I was able to purge the existing
hard dependencies, and it can be quite difficult to strip out non-trivial components
from folly for use in RocksDB. (The prospect of doing that on F14 has changed
my mind on the best approach here.)
But this change creates an optional integration where we can plug in
components from folly at compile time, starting here with F14FastMap to replace
std::unordered_map when possible (probably no public APIs for example). I have
replaced the biggest CPU users of std::unordered_map with compile-time
pluggable UnorderedMap which will use F14FastMap when USE_FOLLY is set.
USE_FOLLY is always set in the Meta-internal buck build, and a simulation of
that is in the Makefile for public CI testing. A full folly build is not needed, but
checking out the full folly repo is much simpler for getting the dependency,
and anything else we might want to optionally integrate in the future.
Some picky details:
* I don't think the distributed mutex stuff is actually used, so it was easy to remove.
* I implemented an alternative to `folly::constexpr_log2` (which is much easier
in C++17 than C++11) so that I could pull out the hard dependencies on
`ConstexprMath.h`
* I had to add noexcept move constructors/operators to some types to make
F14's complainUnlessNothrowMoveAndDestroy check happy, and I added a
macro to make that easier in some common cases.
* Updated Meta-internal buck build to use folly F14Map (always)
No updates to HISTORY.md nor INSTALL.md as this is not (yet?) considered a
production integration for open source users.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9546
Test Plan:
CircleCI tests updated so that a couple of them use folly.
Most internal unit & stress/crash tests updated to use Meta-internal latest folly.
(Note: they should probably use buck but they currently use Makefile.)
Example performance improvement: when filter partitions are pinned in cache,
they are tracked by PartitionedFilterBlockReader::filter_map_ and we can build
a test that exercises that heavily. Build DB with
```
TEST_TMPDIR=/dev/shm/rocksdb ./db_bench -benchmarks=fillrandom -num=10000000 -disable_wal=1 -write_buffer_size=30000000 -bloom_bits=16 -compaction_style=2 -fifo_compaction_max_table_files_size_mb=10000 -fifo_compaction_allow_compaction=0 -partition_index_and_filters
```
and test with (simultaneous runs with & without folly, ~20 times each to see
convergence)
```
TEST_TMPDIR=/dev/shm/rocksdb ./db_bench_folly -readonly -use_existing_db -benchmarks=readrandom -num=10000000 -bloom_bits=16 -compaction_style=2 -fifo_compaction_max_table_files_size_mb=10000 -fifo_compaction_allow_compaction=0 -partition_index_and_filters -duration=40 -pin_l0_filter_and_index_blocks_in_cache
```
Average ops/s no folly: 26229.2
Average ops/s with folly: 26853.3 (+2.4%)
Reviewed By: ajkr
Differential Revision: D34181736
Pulled By: pdillinger
fbshipit-source-id: ffa6ad5104c2880321d8a1aa7187e00ab0d02e94
Summary:
So the user is able to set event listener on the compactor
side.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9821
Test Plan: unittest added
Reviewed By: ajkr
Differential Revision: D35485388
Pulled By: jay-zhuang
fbshipit-source-id: 669d8a3aaee012b75b940470306756c03ffa09b2
Summary:
By default, rocksdb release compiles with `-fno-rtti`. This causes issues when linking with other code that requires RTTI. Documentation indicate that setting the environment variable `USE_RTTI=1` when compiling rocksdb can override this behavior so that `-fno-rtti` is not used (http://rocksdb.org/blog/2017/09/28/rocksdb-5-8-released.html). However, this environment flag had no effect due to a bug in how `CMakeLists.txt` refers to `USE_RTTI`. This PR fixes this issue.
Now, running `USE_RTTI=1 cmake <......>` is correctly recognized by cmake, and causes `ROCKSDB_USE_RTTI `to be defined and `-fno-rtti` not to be issued for release builds. Behavior when USE_RTTI=0 or USE_RTTI is not provided is unchanged.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9760
Reviewed By: jay-zhuang
Differential Revision: D35334552
Pulled By: mrambacher
fbshipit-source-id: e405fcac4e14b246642e52bc7e73b04bf143e5b6
Summary:
1) In case of non-TransactionDB and avoid_flush_during_recovery = true, RocksDB won't
flush the data from WAL to L0 for all column families if possible. As a
result, not all column families can increase their log_numbers, and
min_log_number_to_keep won't change.
2) For transaction DB (.allow_2pc), even with the flush, there may be old WAL files that it must not delete because they can contain data of uncommitted transactions and min_log_number_to_keep won't change.
If we persist a new MANIFEST with
advanced log_numbers for some column families, then during a second
crash after persisting the MANIFEST, RocksDB will see some column
families' log_numbers larger than the corrupted wal, and the "column family inconsistency" error will be hit, causing recovery to fail.
As a solution,
1. the corrupted WALs whose numbers are larger than the
corrupted wal and smaller than the new WAL will be moved to archive folder.
2. Currently, RocksDB DB::Open() may creates and writes to two new MANIFEST files even before recovery succeeds. This PR buffers the edits in a structure and writes to a new MANIFEST after recovery is successful
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9634
Test Plan:
1. Added new unit tests
2. make crast_test -j
Reviewed By: riversand963
Differential Revision: D34463666
Pulled By: akankshamahajan15
fbshipit-source-id: e233d3af0ed4e2028ca0cf051e5a334a0fdc9d19
Summary:
Currently async prefetching is enabled for implicit internal auto readahead in FilePrefetchBuffer if `ReadOptions.async_io` is set. This PR enables async prefetching for `ReadOptions.readahead_size` when `ReadOptions.async_io` is set true.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9827
Test Plan: Update unit test
Reviewed By: anand1976
Differential Revision: D35552129
Pulled By: akankshamahajan15
fbshipit-source-id: d9f9a96672852a591375a21eef15355cf3289f5c
Summary:
Added a Plugin class to the ObjectRegistry. Enabled compile-time and program-time addition of plugins to the Registry.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7949
Reviewed By: mrambacher
Differential Revision: D33517674
Pulled By: pdillinger
fbshipit-source-id: c3e3270aab76a489bfa9e85d78cdfca951912557
Summary:
Options `preserve_deletes` and `iter_start_seqnum` have been removed since 7.0.
This PR removes dead code related to these two removed options.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9825
Test Plan: make check
Reviewed By: akankshamahajan15
Differential Revision: D35517950
Pulled By: riversand963
fbshipit-source-id: 86282ce5ec4087acb94a06a42a1b6d55b1715482
Summary:
Since all plaftorms don't support io_uring. So updated the unit
test to take that into consideration when testing async reads in unit tests.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9819
Test Plan:
valgrind --error-exitcode=2 --leak-check=full ./prefetch_test
--gtest_filter=PrefetchTest2.ReadAsyncWithPosixFS
CircleCI jobs
Reviewed By: pdillinger
Differential Revision: D35469959
Pulled By: akankshamahajan15
fbshipit-source-id: b170459ec816487fc0a13b1d55dbbe4f754b2eba
Summary:
Currently RocksDB reset async_read_in_progress_ in callback
due to which underlying filesystem relying on Poll API won't be called
leading to stale memory access.
In order to fix it, async_read_in_progress_ will be reset after Poll API
is called to make sure underlying file_system waiting on Poll can clear
its state or take appropriate action.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9815
Test Plan: CircleCI tests
Reviewed By: anand1976
Differential Revision: D35451534
Pulled By: akankshamahajan15
fbshipit-source-id: b70ef6251a7aa9ed4876ba5e5100baa33d7d474c
Summary:
When sub compaction is decided for L0->L1 compaction, most of the cases, all L0 files will be involved in all sub compactions. However, it is not always the case. When files are generally (but not strictly) inserted in sequential order, there can be a subset of L0 files invovled. Yet RocksDB always open all those L0 files, and build an iterator, read many of the files' first of last block with expensive readahead. We trim some input files to reduce overhead a little bit.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9802
Test Plan: Add a unit test to cover this case and manually validate the behavior while running the test.
Reviewed By: ajkr
Differential Revision: D35371031
fbshipit-source-id: 701ed7375b5cbe41672e93b38fe8a1503dad08b6
