Summary:
There are too many types of files under util/. Some test related files don't belong to there or just are just loosely related. Mo
ve them to a new directory test_util/, so that util/ is cleaner.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5377
Differential Revision: D15551366
Pulled By: siying
fbshipit-source-id: 0f5c8653832354ef8caa31749c0143815d719e2c
Summary:
util/ means for lower level libraries, so it's a good idea to move the files which requires knowledge to DB out. Create a file/ and move some files there.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5375
Differential Revision: D15550935
Pulled By: siying
fbshipit-source-id: 61a9715dcde5386eebfb43e93f847bba1ae0d3f2
Summary:
Part of compaction cpu goes to processing snapshot list, the larger the list the bigger the overhead. Although the lifetime of most of the snapshots is much shorter than the lifetime of compactions, the compaction conservatively operates on the list of snapshots that it initially obtained. This patch allows the snapshot list to be updated via a callback if the compaction is taking long. This should let the compaction to continue more efficiently with much smaller snapshot list.
For simplicity, to avoid the feature is disabled in two cases: i) When more than one sub-compaction are sharing the same snapshot list, ii) when Range Delete is used in which the range delete aggregator has its own copy of snapshot list.
This fixes the reverted https://github.com/facebook/rocksdb/pull/5099 issue with range deletes.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5278
Differential Revision: D15203291
Pulled By: maysamyabandeh
fbshipit-source-id: fa645611e606aa222c7ce53176dc5bb6f259c258
Summary:
Our daily stress tests are failing after this feature. Reverting temporarily until we figure the reason for test failures.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5269
Differential Revision: D15151285
Pulled By: maysamyabandeh
fbshipit-source-id: e4002b99690a97df30d4b4b58bf0f61e9591bc6e
Summary:
Part of compaction cpu goes to processing snapshot list, the larger the list the bigger the overhead. Although the lifetime of most of the snapshots is much shorter than the lifetime of compactions, the compaction conservatively operates on the list of snapshots that it initially obtained. This patch allows the snapshot list to be updated via a callback if the compaction is taking long. This should let the compaction to continue more efficiently with much smaller snapshot list.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5099
Differential Revision: D15086710
Pulled By: maysamyabandeh
fbshipit-source-id: 7649f56c3b6b2fb334962048150142a3bf9c1a12
Summary:
Introducing Periodic Compactions.
This feature allows all the files in a CF to be periodically compacted. It could help in catching any corruptions that could creep into the DB proactively as every file is constantly getting re-compacted. And also, of course, it helps to cleanup data older than certain threshold.
- Introduced a new option `periodic_compaction_time` to control how long a file can live without being compacted in a CF.
- This works across all levels.
- The files are put in the same level after going through the compaction. (Related files in the same level are picked up as `ExpandInputstoCleanCut` is used).
- Compaction filters, if any, are invoked as usual.
- A new table property, `file_creation_time`, is introduced to implement this feature. This property is set to the time at which the SST file was created (and that time is given by the underlying Env/OS).
This feature can be enabled on its own, or in conjunction with `ttl`. It is possible to set a different time threshold for the bottom level when used in conjunction with ttl. Since `ttl` works only on 0 to last but one levels, you could set `ttl` to, say, 1 day, and `periodic_compaction_time` to, say, 7 days. Since `ttl < periodic_compaction_time` all files in last but one levels keep getting picked up based on ttl, and almost never based on periodic_compaction_time. The files in the bottom level get picked up for compaction based on `periodic_compaction_time`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5166
Differential Revision: D14884441
Pulled By: sagar0
fbshipit-source-id: 408426cbacb409c06386a98632dcf90bfa1bda47
Summary:
This is a feature to sample data-block compressibility and and report them as stats. 1 in N (tunable) blocks is sampled for compressibility using two algorithms:
1. lz4 or snappy for fast compression
2. zstd or zlib for slow but higher compression.
The stats are reported to the caller as raw-bytes and compressed-bytes. The block continues to be compressed for storage using the specified CompressionType.
The db_bench_tool how has a command line option for specifying the sampling rate. It's default value is 0 (no sampling). To test the overhead for a certain value, users can compare the performance of db_bench_tool, varying the sampling rate. It is unlikely to have a noticeable impact for high values like 20.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4842
Differential Revision: D13629011
Pulled By: shobhitdayal
fbshipit-source-id: 14ca668bcab6499b2a1734edf848eb62a4f4fafa
Summary:
Statistics cost too much CPU for some use cases. Add two stats levels
so that people can choose to skip two types of expensive stats, timers and
histograms.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5027
Differential Revision: D14252765
Pulled By: siying
fbshipit-source-id: 75ecec9eaa44c06118229df4f80c366115346592
Summary:
If `CompressionOptions::max_dict_bytes` and/or `CompressionOptions::zstd_max_train_bytes` are set, `SstFileWriter` will now generate files respecting those options.
I refactored the logic a bit for deciding when to use dictionary compression. Previously we plumbed `is_bottommost_level` down to the table builder and used that. However it was kind of confusing in `SstFileWriter`'s context since we don't know what level the file will be ingested to. Instead, now the higher-level callers (e.g., flush, compaction, file writer) are responsible for building the right `CompressionOptions` to give the table builder.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4978
Differential Revision: D14060763
Pulled By: ajkr
fbshipit-source-id: dc802c327896df2b319dc162d6acc82b9cdb452a
Summary:
Our previous approach was to train one compression dictionary per compaction, using the first output SST to train a dictionary, and then applying it on subsequent SSTs in the same compaction. While this was great for minimizing CPU/memory/I/O overhead, it did not achieve good compression ratios in practice. In our most promising potential use case, moderate reductions in a dictionary's scope make a major difference on compression ratio.
So, this PR changes compression dictionary to be scoped per-SST. It accepts the tradeoff during table building to use more memory and CPU. Important changes include:
- The `BlockBasedTableBuilder` has a new state when dictionary compression is in-use: `kBuffered`. In that state it accumulates uncompressed data in-memory whenever `Add` is called.
- After accumulating target file size bytes or calling `BlockBasedTableBuilder::Finish`, a `BlockBasedTableBuilder` moves to the `kUnbuffered` state. The transition (`EnterUnbuffered()`) involves sampling the buffered data, training a dictionary, and compressing/writing out all buffered data. In the `kUnbuffered` state, a `BlockBasedTableBuilder` behaves the same as before -- blocks are compressed/written out as soon as they fill up.
- Samples are now whole uncompressed data blocks, except the final sample may be a partial data block so we don't breach the user's configured `max_dict_bytes` or `zstd_max_train_bytes`. The dictionary trainer is supposed to work better when we pass it real units of compression. Previously we were passing 64-byte KV samples which was not realistic.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4952
Differential Revision: D13967980
Pulled By: ajkr
fbshipit-source-id: 82bea6f7537e1529c7a1a4cdee84585f5949300f
Summary:
We found that the behavior of CompactionFilter::IgnoreSnapshots() = false isn't
what we have expected. We thought that snapshot will always be preserved.
However, we just realized that, if no snapshot is created while compaction
starts, and a snapshot is created after that, the data seen from the snapshot
can successfully be dropped by the compaction. This creates a strange behavior
to the feature, which is hard to explain. Like what is documented in code
comment, this feature is not very useful with snapshot anyway. The decision
is to deprecate the feature.
We keep the function to avoid to break users code. However, we will fail
compactions if false is returned.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4954
Differential Revision: D13981900
Pulled By: siying
fbshipit-source-id: 2db8c2c3865acd86a28dca625945d1481b1d1e36
Summary:
Fix the ouput overlap bug when using subcompactions, the upper bound of output
file was extended incorrectly.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4898
Differential Revision: D13736107
Pulled By: ajkr
fbshipit-source-id: 21dca09f81d5f07bf2766bf566f9b50dcab7d8e3
Summary:
FlushMemTablesToOutputFiles calls FlushMemTableToOutputFile for each column family. The patch moves the take-snapshot logic to outside FlushMemTableToOutputFile so that it does it once for all the flushes. This also addresses a deadlock issue for resetting the managed snapshot of job_snapshot in the 2nd call to FlushMemTableToOutputFile.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4934
Differential Revision: D13900747
Pulled By: maysamyabandeh
fbshipit-source-id: f3cd650c5fff24cf95c1aaf8a10c149d42bf042c
Summary:
Measure CPU time consumed for a compaction and report it in the stats report
Enable NowCPUNanos() to work for MacOS
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4889
Differential Revision: D13701276
Pulled By: zinoale
fbshipit-source-id: 5024e5bbccd4dd10fd90d947870237f436445055
Summary:
While stepping through the code I noticed that there is a redundant call to TableFileName.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4925
Differential Revision: D13845749
Pulled By: sagar0
fbshipit-source-id: 31db45716b4d720e0e0350dd457b49d6f1848e7d
Summary:
Now that v2 is fully functional, the v1 aggregator is removed.
The v2 aggregator has been renamed.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4778
Differential Revision: D13495930
Pulled By: abhimadan
fbshipit-source-id: 9d69500a60a283e79b6c4fa938fc68a8aa4d40d6
Summary:
RangeDelAggregatorV2 now supports ShouldDelete calls on
snapshot stripes and creation of range tombstone compaction iterators.
RangeDelAggregator is no longer used on any non-test code path, and will
be removed in a future commit.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4758
Differential Revision: D13439254
Pulled By: abhimadan
fbshipit-source-id: fe105bcf8e3d4a2df37a622d5510843cd71b0401
Summary:
It is possible to see a situation like the following when
subcompactions are enabled:
1. A subcompaction boundary is set to `[b, e)`.
2. The first output file in a subcompaction has `c@20` as its smallest key
3. The range tombstone `[a, d)30` is encountered.
4. The tombstone is written to the range-del meta block and the new
smallest key is set to `b@0` (since no keys in this subcompaction's
output can be smaller than `b`).
5. A key `b@10` in a lower level will now reappear, since it is not
covered by the truncated start key `b@0`.
In general, unless the smallest data key in a file has a seqnum of 0, it
is not safe to truncate a tombstone at the start key to have a seqnum of
0, since it can expose keys with a seqnum greater than 0 but less than
the tombstone's actual seqnum.
To fix this, when the lower bound of a file is from the subcompaction
boundaries, we now set the seqnum of an artificially extended smallest
key to the tombstone's seqnum. This is safe because subcompactions
operate over disjoint sets of keys, and the subcompactions that can
experience this problem are not the first subcompaction (which is
unbounded on the left).
Furthermore, there is now an assertion to detect the described anomalous
case.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4723
Differential Revision: D13236188
Pulled By: abhimadan
fbshipit-source-id: a6da6a113f2de1e2ff307ca72e055300c8fe5692
Summary:
The old RangeDelAggregator did expensive pre-processing work
to create a collapsed, binary-searchable representation of range
tombstones. With FragmentedRangeTombstoneIterator, much of this work is
now unnecessary. RangeDelAggregatorV2 takes advantage of this by seeking
in each iterator to find a covering tombstone in ShouldDelete, while
doing minimal work in AddTombstones. The old RangeDelAggregator is still
used during flush/compaction for now, though RangeDelAggregatorV2 will
support those uses in a future PR.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4649
Differential Revision: D13146964
Pulled By: abhimadan
fbshipit-source-id: be29a4c020fc440500c137216fcc1cf529571eb3
Summary:
`GenSubcompactionBoundaries` calls `VersionSet::ApproximateSize` which gets BlockBasedTableReader for every file and seeks in its index block to find `key`'s offset. If the table or index block aren't in memory already, this involves I/O. This can be improved by releasing DB mutex when calling ApproximateSize.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4630
Differential Revision: D13052653
Pulled By: miasantreble
fbshipit-source-id: cae31d46d10d0860fa8a26b8d5154b2d17d1685f
Summary:
Ran the following commands to recursively change all the files under RocksDB:
```
find . -type f -name "*.cc" -exec sed -i 's/ unique_ptr/ std::unique_ptr/g' {} +
find . -type f -name "*.cc" -exec sed -i 's/<unique_ptr/<std::unique_ptr/g' {} +
find . -type f -name "*.cc" -exec sed -i 's/ shared_ptr/ std::shared_ptr/g' {} +
find . -type f -name "*.cc" -exec sed -i 's/<shared_ptr/<std::shared_ptr/g' {} +
```
Running `make format` updated some formatting on the files touched.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4638
Differential Revision: D12934992
Pulled By: sagar0
fbshipit-source-id: 45a15d23c230cdd64c08f9c0243e5183934338a8
Summary:
When there's a gap between files, we do not need to output tombstones starting at the next output file's begin key to the current output file.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4592
Differential Revision: D12808627
Pulled By: ajkr
fbshipit-source-id: 77c8b2e7523a95b1cd6611194144092c06acb505
Summary:
We would like to collect file-system-level statistics including file name, offset, length, return code, latency, etc., which requires to add callbacks to intercept file IO function calls when RocksDB is running.
To collect file-system-level statistics, users can inherit the class `EventListener`, as in `TestFileOperationListener `. Note that `TestFileOperationListener::ShouldBeNotifiedOnFileIO()` returns true.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/3933
Differential Revision: D10219571
Pulled By: riversand963
fbshipit-source-id: 7acc577a2d31097766a27adb6f78eaf8b1e8ff15
Summary:
To more accurately truncate range tombstones at SST boundaries,
we now represent them in RangeDelAggregator using InternalKeys, which
are end-key-exclusive as they were before this change.
During compaction, "atomic compaction unit boundaries" (the range of
keys contained in neighbouring and overlaping SSTs) are propagated down
to RangeDelAggregator to truncate range tombstones at those boundariies
instead. See https://github.com/facebook/rocksdb/pull/4432#discussion_r221072219 and https://github.com/facebook/rocksdb/pull/4432#discussion_r221138683
for motivating examples.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4432
Differential Revision: D10263952
Pulled By: abhimadan
fbshipit-source-id: 2fe85ff8a02b3a6a2de2edfe708012797a7bd579
Summary:
I have a PR to start calling `OnTableFileCreated` for empty SSTs: #4307. However, it is a behavior change so should not go into a patch release.
This PR adds back a check to make sure range deletions at least exist before starting file creation. This PR should be safe to backport to earlier versions.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4311
Differential Revision: D9493734
Pulled By: ajkr
fbshipit-source-id: f0d43cda4cfd904f133cfe3a6eb622f52a9ccbe8
Summary:
The API comment on `OnTableFileCreationStarted` (b6280d01f9/include/rocksdb/listener.h (L331-L333)) led users to believe a call to `OnTableFileCreationStarted` will always be matched with a call to `OnTableFileCreated`. However, we were skipping the `OnTableFileCreated` call in one case: no error happens but also no file is generated since there's no data.
This PR adds the call to `OnTableFileCreated` for that case. The filename will be "(nil)" and the size will be zero.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4307
Differential Revision: D9485201
Pulled By: ajkr
fbshipit-source-id: 2f077ec7913f128487aae2624c69a50762394df6
Summary:
We want to sample the file I/O issued by RocksDB and report the function calls. This requires us to include the file paths otherwise it's hard to tell what has been going on.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4039
Differential Revision: D8670178
Pulled By: riversand963
fbshipit-source-id: 97ee806d1c583a2983e28e213ee764dc6ac28f7a
Summary:
Add a unit test to check that iterators release data blocks after it has moved away from it. Verify the same for compaction input iterators.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4170
Differential Revision: D8962513
Pulled By: siying
fbshipit-source-id: 05a5b604d7d29887fb488f2cda7286f554a14407
Summary:
Do not consider the range tombstone sentinel key as causing 2 adjacent
sstables in a level to overlap. When a range tombstone's end key is the
largest key in an sstable, the sstable's end key is so to a "sentinel"
value that is the smallest key in the next sstable with a sequence
number of kMaxSequenceNumber. This "sentinel" is guaranteed to not
overlap in internal-key space with the next sstable. Unfortunately,
GetOverlappingFiles uses user-keys to determine overlap and was thus
considering 2 adjacent sstables in a level to overlap if they were
separated by this sentinel key. This in turn would cause compactions to
be larger than necessary.
Note that this conflicts with
https://github.com/facebook/rocksdb/pull/2769 and cases
`DBRangeDelTest.CompactionTreatsSplitInputLevelDeletionAtomically` to
fail.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4050
Differential Revision: D8844423
Pulled By: ajkr
fbshipit-source-id: df3f9f1db8f4cff2bff77376b98b83c2ae1d155b
Summary:
This fixes the same performance issue that #3992 fixes but with much more invasive cleanup.
I'm more excited about this PR because it paves the way for fixing another problem we uncovered at Cockroach where range deletion tombstones can cause massive compactions. For example, suppose L4 contains deletions from [a, c) and [x, z) and no other keys, and L5 is entirely empty. L6, however, is full of data. When compacting L4 -> L5, we'll end up with one file that spans, massively, from [a, z). When we go to compact L5 -> L6, we'll have to rewrite all of L6! If, instead of range deletions in L4, we had keys a, b, x, y, and z, RocksDB would have been smart enough to create two files in L5: one for a and b and another for x, y, and z.
With the changes in this PR, it will be possible to adjust the compaction logic to split tombstones/start new output files when they would span too many files in the grandparent level.
ajkr please take a look when you have a minute!
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4014
Differential Revision: D8773253
Pulled By: ajkr
fbshipit-source-id: ec62fa85f648fdebe1380b83ed997f9baec35677
Summary:
clang analyze is giving the following warnings:
> db/compaction_job.cc:1178:16: warning: Called C++ object pointer is null
} else if (meta->smallest.size() > 0) {
^~~~~~~~~~~~~~~~~~~~~
db/compaction_job.cc:1201:33: warning: Access to field 'marked_for_compaction' results in a dereference of a null pointer (loaded from variable 'meta')
meta->marked_for_compaction = sub_compact->builder->NeedCompact();
~~~~
db/version_set.cc:2770:26: warning: Called C++ object pointer is null
uint32_t cf_id = last_writer->cfd->GetID();
^~~~~~~~~~~~~~~~~~~~~~~~~
Closes https://github.com/facebook/rocksdb/pull/4072
Differential Revision: D8685852
Pulled By: miasantreble
fbshipit-source-id: b0e2fd9dfc1cbba2317723e09886384b9b1c9085
Summary:
Currently, if RocksDB encounters errors during a write operation (user requested or BG operations), it sets DBImpl::bg_error_ and fails subsequent writes. This PR allows the DB to be resumed for certain classes of errors. It consists of 3 parts -
1. Introduce Status::Severity in rocksdb::Status to indicate whether a given error can be recovered from or not
2. Refactor the error handling code so that setting bg_error_ and deciding on severity is in one place
3. Provide an API for the user to clear the error and resume the DB instance
This whole change is broken up into multiple PRs. Initially, we only allow clearing the error for Status::NoSpace() errors during background flush/compaction. Subsequent PRs will expand this to include more errors and foreground operations such as Put(), and implement a polling mechanism for out-of-space errors.
Closes https://github.com/facebook/rocksdb/pull/3997
Differential Revision: D8653831
Pulled By: anand1976
fbshipit-source-id: 6dc835c76122443a7668497c0226b4f072bc6afd
Summary:
…ression
For `CompressionType` we have options `compression` and `bottommost_compression`. Thus, to make the compression options consitent with the compression type when bottommost_compression is enabled, we add the bottommost_compression_opts
Closes https://github.com/facebook/rocksdb/pull/3985
Reviewed By: riversand963
Differential Revision: D8385911
Pulled By: zhichao-cao
fbshipit-source-id: 07bc533dd61bcf1cef5927d8d62901c13d38d5fc
Summary:
Add a new table property, rocksdb.num.range-deletions, which tracks the
number of range deletions in a block-based table. Range deletions are no
longer counted in rocksdb.num.entries; as discovered in PR #3778, there
are various code paths that implicitly assume that rocksdb.num.entries
counts only true keys, not range deletions.
/cc ajkr nvanbenschoten
Closes https://github.com/facebook/rocksdb/pull/4016
Differential Revision: D8527575
Pulled By: ajkr
fbshipit-source-id: 92e7edbe78fda53756a558013c9fb496e7764fd7
Summary:
For example calling CompactionFilter is always timed and gives the user no way to disable.
This PR will disable the timer if `Statistics::stats_level_` (which is part of DBOptions) is `kExceptDetailedTimers`
Closes https://github.com/facebook/rocksdb/pull/4029
Differential Revision: D8583670
Pulled By: miasantreble
fbshipit-source-id: 913be9fe433ae0c06e88193b59d41920a532307f
Summary:
Verify table will load SST into `TableCache`
it occupy memory & `TableCache`‘s capacity ...
but no logic use them
it's unnecessary ...
so , we verify them after all sub compact finished
Closes https://github.com/facebook/rocksdb/pull/3979
Differential Revision: D8389946
Pulled By: ajkr
fbshipit-source-id: 54bd4f474f9e7b3accf39c3068b1f36a27ec4c49
Summary:
Currently it is not possible to change bloom filter config without restart the db, which is causing a lot of operational complexity for users.
This PR aims to make it possible to dynamically change bloom filter config.
Closes https://github.com/facebook/rocksdb/pull/3601
Differential Revision: D7253114
Pulled By: miasantreble
fbshipit-source-id: f22595437d3e0b86c95918c484502de2ceca120c
Summary:
Sometimes we want to compact files as fast as possible, but don't want to set a large `max_subcompactions` in the `DBOptions` by default.
I add a `max_subcompactions` options to `CompactionOptions` so that we can choose a proper concurrency dynamically.
Closes https://github.com/facebook/rocksdb/pull/3775
Differential Revision: D7792357
Pulled By: ajkr
fbshipit-source-id: 94f54c3784dce69e40a229721a79a97e80cd6a6c
Summary:
This PR comments out the rest of the unused arguments which allow us to turn on the -Wunused-parameter flag. This is the second part of a codemod relating to https://github.com/facebook/rocksdb/pull/3557.
Closes https://github.com/facebook/rocksdb/pull/3662
Differential Revision: D7426121
Pulled By: Dayvedde
fbshipit-source-id: 223994923b42bd4953eb016a0129e47560f7e352
Summary:
Add `compaction_reason` as part of event log for event `compaction started`.
Add counters for each `CompactionReason`.
Closes https://github.com/facebook/rocksdb/pull/3679
Differential Revision: D7550348
Pulled By: riversand963
fbshipit-source-id: a19cff3a678c785aa5ef41aac78b9a5968fcc34d
Summary:
In this case, we add input files of compaction, not outputs.
Closes https://github.com/facebook/rocksdb/pull/3686
Differential Revision: D7556781
Pulled By: ajkr
fbshipit-source-id: ae135bb6eda60db8f275a9ba2d21c18aaadef5b7
Summary:
In this change, an option to set different paths for different column families is added.
This option is set via cf_paths setting of ColumnFamilyOptions. This option will work in a similar fashion to db_paths setting. Cf_paths is a vector of Dbpath values which contains a pair of the absolute path and target size. Multiple levels in a Column family can go to different paths if cf_paths has more than one path.
To maintain backward compatibility, if cf_paths is not specified for a column family, db_paths setting will be used. Note that, if db_paths setting is also not specified, RocksDB already has code to use db_name as the only path.
Changes :
1) A new member "cf_paths" is added to ImmutableCfOptions. This is set, based on cf_paths setting of ColumnFamilyOptions and db_paths setting of ImmutableDbOptions. This member is used to identify the path information whenever files are accessed.
2) Validation checks are added for cf_paths setting based on existing checks for db_paths setting.
3) DestroyDB, PurgeObsoleteFiles etc. are edited to support multiple cf_paths.
4) Unit tests are added appropriately.
Closes https://github.com/facebook/rocksdb/pull/3102
Differential Revision: D6951697
Pulled By: ajkr
fbshipit-source-id: 60d2262862b0a8fd6605b09ccb0da32bb331787d
