Summary:
Add the new Append and PositionedAppend API to env WritableFile. User is able to benefit from the write checksum handoff API when using the legacy Env classes. FileSystem already implemented the checksum handoff API.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8071
Test Plan: make check, added new unit test.
Reviewed By: anand1976
Differential Revision: D27177043
Pulled By: zhichao-cao
fbshipit-source-id: 430c8331fc81099fa6d00f4fff703b68b9e8080e
Summary:
Currently, a few ldb commands do not check the execution result of
database operations. This PR checks the execution results and tries to
improve the error reporting.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8072
Test Plan:
```
make check
```
and
```
ASSERT_STATUS_CHECKED=1 make -j20 ldb
python tools/ldb_test.py
```
Reviewed By: zhichao-cao
Differential Revision: D27152466
Pulled By: riversand963
fbshipit-source-id: b94220496a4b3591b61c1d350f665860a6579f30
Summary:
In previous codebase, if WAL is used, all the retryable IO Error will be treated as hard error. So write is stalled. In this PR, the retryable IO error from WAL sync is separated from SST file flush io error. If WAL Sync is ok and retryable IO Error only happens during SST flush, the error is mapped to soft error. So user can continue insert to Memtable and append to WAL.
Resolve the bug that if WAL sync fails, the memtable status does not roll back due to calling PickMemtable early than calling and checking SyncClosedLog.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8049
Test Plan: added new unit test, make check
Reviewed By: anand1976
Differential Revision: D26965529
Pulled By: zhichao-cao
fbshipit-source-id: f5fecb66602212523c92ee49d7edcb6065982410
Summary:
WriteController had a number of issues:
* It could introduce a delay of 1ms even if the write rate never exceeded the
configured delayed_write_rate.
* The DB-wide delayed_write_rate could be exceeded in a number of ways
with multiple column families:
* Wiping all pending delay "debts" when another column family joins
the delay with GetDelayToken().
* Resetting last_refill_time_ to (now + sleep amount) means each
column family can write with delayed_write_rate for large writes.
* Updating bytes_left_ for a partial refill without updating
last_refill_time_ would essentially give out random bonuses,
especially to medium-sized writes.
Now the code is much simpler, with these issues fixed. See comments in
the new code and new (replacement) tests.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8064
Test Plan: new tests, better than old tests
Reviewed By: mrambacher
Differential Revision: D27064936
Pulled By: pdillinger
fbshipit-source-id: 497c23fe6819340b8f3d440bd634d8a2bc47323f
Summary:
Add statistics and info log for error handler: counters for bg error, bg io error, bg retryable io error, auto resume, auto resume total retry, and auto resume sucess; Histogram for auto resume retry count in each recovery call.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8050
Test Plan: make check and add test to error_handler_fs_test
Reviewed By: anand1976
Differential Revision: D26990565
Pulled By: zhichao-cao
fbshipit-source-id: 49f71e8ea4e9db8b189943976404205b56ab883f
Summary:
Extend support to track blob files in SST File manager.
This PR notifies SstFileManager whenever a new blob file is created,
via OnAddFile and an obsolete blob file deleted via OnDeleteFile
and delete file via ScheduleFileDeletion.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8037
Test Plan: Add new unit tests
Reviewed By: ltamasi
Differential Revision: D26891237
Pulled By: akankshamahajan15
fbshipit-source-id: 04c69ccfda2a73782fd5c51982dae58dd11979b6
Summary:
support getUsage and getPinnedUsage in JavaAPI for Cache
also fix a typo in LRUCacheTest.java that the highPriPoolRatio is not valid(set 5, I guess it means 0.05)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7925
Reviewed By: mrambacher
Differential Revision: D26900241
Pulled By: ajkr
fbshipit-source-id: 735d1e40a16fa8919c89c7c7154ba7f81208ec33
Summary:
The new options are:
* compact0 - compact L0 into L1 using one thread
* compact1 - compact L1 into L2 using one thread
* flush - flush memtable
* waitforcompaction - wait for compaction to finish
These are useful for reproducible benchmarks to help get the LSM tree shape
into a deterministic state. I wrote about this at:
http://smalldatum.blogspot.com/2021/02/read-only-benchmarks-with-lsm-are.html
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8027
Reviewed By: riversand963
Differential Revision: D27053861
Pulled By: ajkr
fbshipit-source-id: 1646f35584a3db03740fbeb47d91c3f00fb35d6e
Summary:
Fixes 3 minor Javadoc copy-paste errors in the `RocksDB#newIterator()` and `Transaction#getIterator()` variants that take a column family handle but are talking about iterating over "the database" or "the default column family".
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8034
Reviewed By: jay-zhuang
Differential Revision: D26877667
Pulled By: mrambacher
fbshipit-source-id: 95dd95b667c496e389f221acc9a91b340e4b63bf
Summary:
These classes were wraps of Env that provided only extensions to the FileSystem functionality. Changed the classes to be FileSystems and the wraps to be of the CompositeEnvWrapper.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7968
Reviewed By: anand1976
Differential Revision: D26900253
Pulled By: mrambacher
fbshipit-source-id: 94001d8024a3c54a1c11adadca2bac66c3af2a77
Summary:
When timestamp is enabled, key comparison should take this into account.
In `BlockBasedTableReader::Get()`, `BlockBasedTableReader::MultiGet()`,
assume the target key is `key`, and the timestamp upper bound is `ts`.
The highest key in current block is (key, ts1), while the lowest key in next
block is (key, ts2).
If
```
ts1 > ts > ts2
```
then
```
(key, ts1) < (key, ts) < (key, ts2)
```
It can be shown that if `Compare()` is used, then we will mistakenly skip the next
block. Instead, we should use `CompareWithoutTimestamp()`.
The majority of this PR makes some existing tests in `db_with_timestamp_basic_test.cc`
parameterized so that different index types can be tested. A new unit test is
also added for more coverage.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8062
Test Plan: make check
Reviewed By: ltamasi
Differential Revision: D27057557
Pulled By: riversand963
fbshipit-source-id: c1062fa7c159ed600a1ad7e461531d52265021f1
Summary:
For performance purposes, the lower level routines were changed to use a SystemClock* instead of a std::shared_ptr<SystemClock>. The shared ptr has some performance degradation on certain hardware classes.
For most of the system, there is no risk of the pointer being deleted/invalid because the shared_ptr will be stored elsewhere. For example, the ImmutableDBOptions stores the Env which has a std::shared_ptr<SystemClock> in it. The SystemClock* within the ImmutableDBOptions is essentially a "short cut" to gain access to this constant resource.
There were a few classes (PeriodicWorkScheduler?) where the "short cut" property did not hold. In those cases, the shared pointer was preserved.
Using db_bench readrandom perf_level=3 on my EC2 box, this change performed as well or better than 6.17:
6.17: readrandom : 28.046 micros/op 854902 ops/sec; 61.3 MB/s (355999 of 355999 found)
6.18: readrandom : 32.615 micros/op 735306 ops/sec; 52.7 MB/s (290999 of 290999 found)
PR: readrandom : 27.500 micros/op 871909 ops/sec; 62.5 MB/s (367999 of 367999 found)
(Note that the times for 6.18 are prior to revert of the SystemClock).
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8033
Reviewed By: pdillinger
Differential Revision: D27014563
Pulled By: mrambacher
fbshipit-source-id: ad0459eba03182e454391b5926bf5cdd45657b67
Summary:
CompactionDeletionTriggerReopen was observed to be flaky recently:
https://app.circleci.com/pipelines/github/facebook/rocksdb/6030/workflows/787af4f3-b9f7-4645-8e8d-1fb0ebf05539/jobs/101451.
I went through it and the related tests and arrived at different
conclusions on what constraints we can expect on DB size. Some
constraints got looser and some got tighter. The particular constraint
that flaked got a lot looser so at least the flake linked above would have been prevented.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8036
Reviewed By: riversand963
Differential Revision: D26862566
Pulled By: ajkr
fbshipit-source-id: 3512b86b4fb41aeecae32e1c7382c03916d88d88
Summary:
`DBTest.GetLiveBlobFiles` and `ObsoleteFilesTest.BlobFiles` both modify the
current `Version` in their setup phase, implicitly assuming that no other
threads would touch the `Version` while this is happening. The periodic
stats dumper thread violates this assumption; the patch fixes this by
disabling it in the affected test cases. (Note: the data race is
harmless in the sense that it only affects test code.)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8055
Test Plan:
```
COMPILE_WITH_TSAN=1 make db_test -j24
gtest-parallel --repeat=10000 ./db_test --gtest_filter="*GetLiveBlobFiles"
COMPILE_WITH_TSAN=1 make obsolete_files_test -j24
gtest-parallel --repeat=10000 ./obsolete_files_test --gtest_filter="*BlobFiles"
```
Reviewed By: riversand963
Differential Revision: D27022715
Pulled By: ltamasi
fbshipit-source-id: b6cc77ed63d8bc1cbe0603522ff1a572182fc9ab
Summary:
This is for cases that do not meet the Facebook criteria for
SKIP (see new comments). Also made ROCKSDB_GTEST_{SKIP,BYPASS} print the
message because gtest doesn't ever seem to.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8048
Test Plan: manual inspection of ./ribbon_test output, CI
Reviewed By: mrambacher
Differential Revision: D26953688
Pulled By: pdillinger
fbshipit-source-id: c914eaffe7d419db6ab90a193d474531e23582e5
Summary:
a trial gtest upgrade discovered some parameterized tests missing instantiation. By some miracle, they still pass.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8051
Test Plan: thisisthetest
Reviewed By: mrambacher
Differential Revision: D27003684
Pulled By: pdillinger
fbshipit-source-id: cde1cab1551fb282f67d462d46574bd30bd5e61f
Summary:
This API can be used for things like determining how much space
can be freed up by deleting a particular backup, etc.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8042
Test Plan:
validation of the API added to many existing backup unit
tests
Reviewed By: mrambacher
Differential Revision: D26936577
Pulled By: pdillinger
fbshipit-source-id: f0bbd90f0917b9781a6837652fb4616d9247816a
Summary:
This PR
- adds a class `ManifestTailer` that inherits from `VersionEditHandlerPointInTime`. `ManifestTailer::Iterate()` can be called multiple times to tail the primary instance's MANIFEST and apply the changes to the secondary,
- updates the implementation of `ReactiveVersionSet::ReadAndApply` to use this class,
- removes unused code in version_set.cc,
- updates existing tests, e.g. removing deleted sync points from unit tests,
- adds a new test to address the bug in https://github.com/facebook/rocksdb/issues/7815.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7998
Test Plan:
make check
Existing and newly-added tests in version_set_test.cc and db_secondary_test.cc
Reviewed By: jay-zhuang
Differential Revision: D26926641
Pulled By: riversand963
fbshipit-source-id: 8d4dd15db0ba863c213f743e33b5a207e948c980
Summary:
The variable `byteCompressionType` is only assigned values of primitive type and is never 'null', but it is declared with the boxed type 'Byte'.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7981
Reviewed By: ajkr
Differential Revision: D26546600
Pulled By: jay-zhuang
fbshipit-source-id: 07b579cdfcfc2262a448ca3626e216416fd05892
Summary:
This PR adds support for custom file systems to ldb and sst_dump by adding command line options for specifying --fs_uri and --backup_fs uri (for ldb backup/restore commands). fs_uri is already supported in db_bench and db_stress, and there is already support in ldb and db stress for specifying customized envs.
The PR also fixes what looks like a bug in the ldb backup/restore commands. As it is right now, backups can only be made from and to the same environment/file system which does not seem to be the intended behavior. This PR makes it possible to do/restore backups between different envs/file systems.
Example:
`./ldb backup --fs_uri=zenfs://dev:nvme2n1 --backup_fs_uri=posix:// --backup_dir=/tmp/my_rocksdb_backup --db=rocksdbtest/dbbench
`
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8010
Reviewed By: jay-zhuang
Differential Revision: D26904654
Pulled By: ajkr
fbshipit-source-id: 9b695ed8b944fcc6b27c4daaa9f52e87ee2c1fb4
Summary:
Removed confusing, awkward, and undocumented internal API
ReadOneLine and replaced with very simple LineFileReader.
In refactoring backupable_db.cc, this has the side benefit of
removing the arbitrary cap on the size of backup metadata files.
Also added Status::MustCheck to make it easy to mark a Status as
"must check." Using this, I can ensure that after
LineFileReader::ReadLine returns false the caller checks GetStatus().
Also removed some excessive conditional compilation in status.h
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8026
Test Plan: added unit test, and running tests with ASSERT_STATUS_CHECKED
Reviewed By: mrambacher
Differential Revision: D26831687
Pulled By: pdillinger
fbshipit-source-id: ef749c265a7a26bb13cd44f6f0f97db2955f6f0f
Summary:
New comment for share_files_with_checksum:
// Only used if share_table_files is set to true. Setting to false is
// DEPRECATED and potentially dangerous because in that case BackupEngine
// can lose data if backing up databases with distinct or divergent
// history, for example if restoring from a backup other than the latest,
// writing to the DB, and creating another backup. Setting to true (default)
// prevents these issues by ensuring that different table files (SSTs) with
// the same number are treated as distinct. See
// share_files_with_checksum_naming and ShareFilesNaming.
I have also removed interim option kFlagMatchInterimNaming, which is no
longer needed and was never needed for correct+compatible operation
(just performance).
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8020
Test Plan:
tests updated. Backward+forward compatibility verified with
SHORT_TEST=1 check_format_compatible.sh. ldb uses default backup
options, and I manually verified shared_checksum in
/tmp/rocksdb_format_compatible_peterd/bak/current/ after run.
Reviewed By: ajkr
Differential Revision: D26786331
Pulled By: pdillinger
fbshipit-source-id: 36f968dfef1f5cacbd65154abe1d846151a55130
Summary:
Haven't seen any production issues with new Bloom filter and
it's now > 1 year old (added in 6.6.0).
Updated check_format_compatible.sh and HISTORY.md
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8017
Test Plan: tests updated (or prior bugs fixed)
Reviewed By: ajkr
Differential Revision: D26762197
Pulled By: pdillinger
fbshipit-source-id: 0e755c46b443087c1544da0fd545beb9c403d1c2
Summary:
## 1. Bug description:
When RocksDB Checkpoint, it may be stuck in `WaitUntilFlushWouldNotStallWrites` method.
## 2. Simple analysis of the reasons:
### 2.1 Configuration parameters:
```yaml
Compaction Style : Universal
max_write_buffer_number : 4
min_write_buffer_number_to_merge : 3
```
Checkpoint is usually very fast. When the Checkpoint is executed, `WaitUntilFlushWouldNotStallWrites` is called. If there are 2 Immutable MemTables, which are less than `min_write_buffer_number_to_merge`, they will not be flushed. But will enter this code.
```c++
// method: GetWriteStallConditionAndCause
if (mutable_cf_options.max_write_buffer_number> 3 &&
num_unflushed_memtables >=
mutable_cf_options.max_write_buffer_number-1) {
return {WriteStallCondition::kDelayed, WriteStallCause::kMemtableLimit};
}
```
code link: fbed72f03c/db/column_family.cc (L847)
Checkpoint thought there was a FlushJob, but it didn't. So will always wait.
### 2.2 solution:
Increase the restriction: the `number of Immutable MemTable` >= `min_write_buffer_number_to_merge will wait`.
If there are other better solutions, you can correct me.
### 2.3 Code that can reproduce the problem:
https://github.com/1996fanrui/fanrui-learning/blob/flink-1.12/module-java/src/main/java/com/dream/rocksdb/RocksDBCheckpointStuck.java
## 3. Interesting point
This bug will be triggered only when `the number of sorted runs >= level0_file_num_compaction_trigger`.
Because there is a break in WaitUntilFlushWouldNotStallWrites.
```c++
if (cfd->imm()->NumNotFlushed() <
cfd->ioptions()->min_write_buffer_number_to_merge &&
vstorage->l0_delay_trigger_count() <
mutable_cf_options.level0_file_num_compaction_trigger) {
break;
}
```
code link: fbed72f03c/db/db_impl/db_impl_compaction_flush.cc (L1974)
Universal may have `l0_delay_trigger_count() >= level0_file_num_compaction_trigger`, so this bug is triggered.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7921
Reviewed By: jay-zhuang
Differential Revision: D26900559
Pulled By: ajkr
fbshipit-source-id: 133c1252dad7393753f04a47590b68c7d8e670df
Summary:
On x86_64, this makes the struct 8 bytes smaller, so creating a PerfStepTimer on the stack will use slightly less stack space.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7931
Reviewed By: jay-zhuang
Differential Revision: D26529470
Pulled By: ajkr
fbshipit-source-id: bbe2e843167152ffa05a5946f1add6621c9849f7
Summary:
For some reason I still cannot figure out, the manual flush in this test
was sometimes producing a third tiny file. I saw it a bunch of times on
ppc64le, but even running a qemu system with that architecture (and
playing with various other options) could not repro. However we did get
an instrumented Travis run to confirm the problem is indeed a third tiny
file - https://travis-ci.org/github/facebook/rocksdb/jobs/761986592. We
can avoid it by filling memtables less full and using manual flush.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8044
Reviewed By: akankshamahajan15
Differential Revision: D26892635
Pulled By: ajkr
fbshipit-source-id: 775c04176931cf01d07cc78fb82cfe3a11beebcf
Summary:
I recently discovered the confusing, undocumented semantics of
Read() functions in the FileSystem and Env APIs. I have added
clarification to the best of my reverse-engineered understanding, and
made a note in HISTORY.md for implementors to check their
implementations, as a subtly non-adherent implementation could lead to
RocksDB quietly ignoring some portion of a file.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8029
Test Plan: no code changes
Reviewed By: anand1976
Differential Revision: D26831698
Pulled By: pdillinger
fbshipit-source-id: 208f97ff6037bc13bb2ef360b987c2640c79bd03
Summary:
The patch does the following:
1) Exposes the amount of data (number of bytes) read from blob files from
`BlobFileReader::GetBlob` / `Version::GetBlob`.
2) Tracks the total number and size of blobs read from blob files during a
compaction (due to garbage collection or compaction filter usage) in
`CompactionIterationStats` and propagates this data to
`InternalStats::CompactionStats` / `CompactionJobStats`.
3) Updates the formulae for write amplification calculations to include the
amount of data read from blob files.
4) Extends the compaction stats dump with a new column `Rblob(GB)` and
a new line containing the total number and size of blob files in the current
`Version` to complement the information about the shape and size of the LSM tree
that's already there.
5) Updates `CompactionJobStats` so that the number of files and amount of data
written by a compaction are broken down per file type (i.e. table/blob file).
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8022
Test Plan: Ran `make check` and `db_bench`.
Reviewed By: riversand963
Differential Revision: D26801199
Pulled By: ltamasi
fbshipit-source-id: 28a5f072048a702643b28cb5971b4099acabbfb2
Summary:
This PR adds SetBufferSize() to the WriteBufferManager object. This enables user code to adjust the global budget for write_buffers based upon other memory conditions such as growth in table reader memory as the dataset grows.
The buffer_size_ member variable is now atomic to match design of other changeable size_t members within WriteBufferManager.
This change is useful as is. However, this change is also essential if someone decides they wanted to enable db_write_buffer_size modifications through the DB::SetOptions() API, i.e. no waste taking this as is.
Any format / spacing changes are due to clang-format as required by check-in automation.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7961
Reviewed By: ajkr
Differential Revision: D26639075
Pulled By: akankshamahajan15
fbshipit-source-id: 0604348caf092d35f44e85715331dc920e5c1033
Summary:
When changing db iterator direction, we may perform a reseek.
Therefore, we should bump the NUMBER_OF_RESEEKS_IN_ITERATION counter.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8015
Test Plan: make check
Reviewed By: ltamasi
Differential Revision: D26755415
Pulled By: riversand963
fbshipit-source-id: 211f51f1a454bcda768fc46c0dce51edeb7f05fe
Summary:
* Adds backup/restore forward/backward compatibility testing
* Adds forward/backward compatibility testing to sst ingestion
* More structure sharing and comments for the lists of branches
comprising each group
* Less reliant on invariants between groups with de-duplication logic
* Restructured for n+1 branch checkout+build steps rather than something
like 3n. Should be much faster despite more checks.
And to make manual runs easier
* On success, restores working trees to original working branch (aborts
early if uncommitted changes) and deletes temporary branch & remote
* Adds SHORT_TEST=1 mode that uses only the oldest version for each
* Adds USE_SSH=1 to use ssh instead of https for github
group
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8012
Test Plan:
a number of manual tests, mostly with SHORT_TEST=1. Using one
version older for any of the groups (except I didn't check
db_backward_only_refs) fails. Changing default format_version to 5
(planned) without updating this script fails as it should, and passes
with appropriate update. Full local run passed (had to remove "2.7.fb.branch"
due to compiler issues, also before this change).
Reviewed By: riversand963
Differential Revision: D26735840
Pulled By: pdillinger
fbshipit-source-id: 1320c22de5674760657e385aa42df9fade8b6fff
Summary:
The patch breaks down the "bytes written" (as well as the "number of output files")
compaction statistics into two, so the values are logged separately for table files
and blob files in the info log, and are shown in separate columns (`Write(GB)` for table
files, `Wblob(GB)` for blob files) when the compaction statistics are dumped.
This will also come in handy for fixing the write amplification statistics, which currently
do not consider the amount of data read from blob files during compaction. (This will
be fixed by an upcoming patch.)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8013
Test Plan: Ran `make check` and `db_bench`.
Reviewed By: riversand963
Differential Revision: D26742156
Pulled By: ltamasi
fbshipit-source-id: 31d18ee8f90438b438ca7ed1ea8cbd92114442d5
Summary:
The checkpointing logic supports passing file level checksums
to the copy_file_cb callback function which is used by the backup code
for detecting corruption during file copies.
However, this is currently implemented only for table files.
This PR extends the checksum retrieval to blob files as well.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8003
Test Plan: Add new test units
Reviewed By: ltamasi
Differential Revision: D26680701
Pulled By: akankshamahajan15
fbshipit-source-id: 1bd1e2464df6e9aa31091d35b8c72786d94cd1c5
Summary:
This is likely a temp fix before we figure out a better way.
PerfStepTimer is used intensively in certain benchmarking/testings. https://github.com/facebook/rocksdb/issues/7858 stores a `shared_ptr` to system clock in PerfStepTimer which gets created each time a `PerfStepTimer` object is created. The atomic operations in `shared_ptr` may add overhead in CPU cycles. Therefore, we change it back to a raw `SystemClock*` for now.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8006
Test Plan: make check
Reviewed By: pdillinger
Differential Revision: D26703560
Pulled By: riversand963
fbshipit-source-id: 519d0769b28da2334bea7d86c848fcc26ee8a17f
Summary:
This change only affects non-schema-critical aspects of the production candidate Ribbon filter. Specifically, it refines choice of internal configuration parameters based on inputs. The changes are minor enough that the schema tests in bloom_test, some of which depend on this, are unaffected. There are also some minor optimizations and refactorings.
This would be a schema change for "smash" Ribbon, to fix some known issues with small filters, but "smash" Ribbon is not accessible in public APIs. Unit test CompactnessAndBacktrackAndFpRate updated to test small and medium-large filters. Run with --thoroughness=100 or so for much better detection power (not appropriate for continuous regression testing).
Homogenous Ribbon:
This change adds internally a Ribbon filter variant we call Homogeneous Ribbon, in collaboration with Stefan Walzer. The expected "result" value for every key is zero, instead of computed from a hash. Entropy for queries not to be false positives comes from free variables ("overhead") in the solution structure, which are populated pseudorandomly. Construction is slightly faster for not tracking result values, and never fails. Instead, FP rate can jump up whenever and whereever entries are packed too tightly. For small structures, we can choose overhead to make this FP rate jump unlikely, as seen in updated unit test CompactnessAndBacktrackAndFpRate.
Unlike standard Ribbon, Homogeneous Ribbon seems to scale to arbitrary number of keys when accepting an FP rate penalty for small pockets of high FP rate in the structure. For example, 64-bit ribbon with 8 solution columns and 10% allocated space overhead for slots seems to achieve about 10.5% space overhead vs. information-theoretic minimum based on its observed FP rate with expected pockets of degradation. (FP rate is close to 1/256.) If targeting a higher FP rate with fewer solution columns, Homogeneous Ribbon can be even more space efficient, because the penalty from degradation is relatively smaller. If targeting a lower FP rate, Homogeneous Ribbon is less space efficient, as more allocated overhead is needed to keep the FP rate impact of degradation relatively under control. The new OptimizeHomogAtScale tool in ribbon_test helps to find these optimal allocation overheads for different numbers of solution columns. And Ribbon widths, with 128-bit Ribbon apparently cutting space overheads in half vs. 64-bit.
Other misc item specifics:
* Ribbon APIs in util/ribbon_config.h now provide configuration data for not just 5% construction failure rate (95% success), but also 50% and 0.1%.
* Note that the Ribbon structure does not exhibit "threshold" behavior as standard Xor filter does, so there is a roughly fixed space penalty to cut construction failure rate in half. Thus, there isn't really an "almost sure" setting.
* Although we can extrapolate settings for large filters, we don't have a good formula for configuring smaller filters (< 2^17 slots or so), and efforts to summarize with a formula have failed. Thus, small data is hard-coded from updated FindOccupancy tool.
* Enhances ApproximateNumEntries for public API Ribbon using more precise data (new API GetNumToAdd), thus a more accurate but not perfect reversal of CalculateSpace. (bloom_test updated to expect the greater precision)
* Move EndianSwapValue from coding.h to coding_lean.h to keep Ribbon code easily transferable from RocksDB
* Add some missing 'const' to member functions
* Small optimization to 128-bit BitParity
* Small refactoring of BandingStorage in ribbon_alg.h to support Homogeneous Ribbon
* CompactnessAndBacktrackAndFpRate now has an "expand" test: on construction failure, a possible alternative to re-seeding hash functions is simply to increase the number of slots (allocated space overhead) and try again with essentially the same hash values. (Start locations will be different roundings of the same scaled hash values--because fastrange not mod.) This seems to be as effective or more effective than re-seeding, as long as we increase the number of slots (m) by roughly m += m/w where w is the Ribbon width. This way, there is effectively an expansion by one slot for each ribbon-width window in the banding. (This approach assumes that getting "bad data" from your hash function is as unlikely as it naturally should be, e.g. no adversary.)
* 32-bit and 16-bit Ribbon configurations are added to ribbon_test for understanding their behavior, e.g. with FindOccupancy. They are not considered useful at this time and not tested with CompactnessAndBacktrackAndFpRate.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7879
Test Plan: unit test updates included
Reviewed By: jay-zhuang
Differential Revision: D26371245
Pulled By: pdillinger
fbshipit-source-id: da6600d90a3785b99ad17a88b2a3027710b4ea3a
