Summary:
With #3983 the size of IndexBlockIter was increased. This had resulted in a regression on P50 latencies in one of our benchmarks. The patch reduces IndexBlockIter size be eliminating active_comparator_ field from the class.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4358
Differential Revision: D9781737
Pulled By: maysamyabandeh
fbshipit-source-id: 71e2b28d90ff0813db9e04b737ae73e185583c52
Summary:
Reverting is needed to unblock a user building against master, who is blocked for multiple days due to a thread-safety issue in `GetEmptyDict`. We haven't been able to fix it quickly, so reverting.
Simply ran `git revert 6c40806e51a89386d2b066fddf73d3fd03a36f65`. There were no merge conflicts.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4347
Differential Revision: D9668365
Pulled By: ajkr
fbshipit-source-id: 0c56334f0a23cf5ee0233d4e4679eae6709739cd
Summary:
As you know, almost all compilers support "pragma once" keyword instead of using include guards. To be keep consistency between header files, all header files are edited.
Besides this, try to fix some warnings about loss of data.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4339
Differential Revision: D9654990
Pulled By: ajkr
fbshipit-source-id: c2cf3d2d03a599847684bed81378c401920ca848
Summary:
In RocksDB, for a given SST file, all data blocks are compressed with the same dictionary. When we compress a block using the dictionary's raw bytes, the compression library first has to digest the dictionary to get it into a usable form. This digestion work is redundant and ideally should be done once per file.
ZSTD offers APIs for the caller to create and reuse a digested dictionary object (`ZSTD_CDict`). In this PR, we call `ZSTD_createCDict` once per file to digest the raw bytes. Then we use `ZSTD_compress_usingCDict` to compress each data block using the pre-digested dictionary. Once the file's created `ZSTD_freeCDict` releases the resources held by the digested dictionary.
There are a couple other changes included in this PR:
- Changed the parameter object for (un)compression functions from `CompressionContext`/`UncompressionContext` to `CompressionInfo`/`UncompressionInfo`. This avoids the previous pattern, where `CompressionContext`/`UncompressionContext` had to be mutated before calling a (un)compression function depending on whether dictionary should be used. I felt that mutation was error-prone so eliminated it.
- Added support for digested uncompression dictionaries (`ZSTD_DDict`) as well. However, this PR does not support reusing them across uncompression calls for the same file. That work is deferred to a later PR when we will store the `ZSTD_DDict` objects in block cache.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4251
Differential Revision: D9257078
Pulled By: ajkr
fbshipit-source-id: 21b8cb6bbdd48e459f1c62343780ab66c0a64438
Summary:
When returning `kNoEntry` from HashIndex lookup, previously we invalidate the
`biter` by set `current_=restarts_`, so that the search can continue to the next
block in case the search result may reside in the next block.
There is one problem: when we are searching for a missing key, if the search
finds a `kNoEntry` and continue the search to the next block, there is also a
non-trivial possibility that the HashIndex return `kNoEntry` too, and the
expensive index iterator `Next()` will happen several times for nothing.
The solution is that if the hash table returns `kNoEntry`, `SeekForGetImpl()` just search the last restart interval for the key. It will stop at the first key that is large than the seek_key, or to the end of the block, and each case will be handled correctly.
Microbenchmark script:
```
TEST_TMPDIR=/dev/shm ./db_bench --benchmarks=fillseq,readtocache,readmissing \
--cache_size=20000000000 --use_data_block_hash_index={true|false}
```
`readmissing` performance (lower is better):
```
binary: 3.6098 micros/op
hash (before applying diff): 4.1048 micros/op
hash (after applying diff): 3.3502 micros/op
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4296
Differential Revision: D9419159
Pulled By: fgwu
fbshipit-source-id: 21e3eedcccbc47a249aa8eb4bf405c9def0b8a05
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:
`BlockBasedTableBuilder::Add()` eventually calls
`DataBlockHashIndexBuilder::EstimateSize()`. The previous implementation
divides the `num_keys` by the `util_ratio_` to get an estimizted `num_buckets`.
Such division is expensive as it happens in every
`BlockBasedTableBuilder::Add()`.
This diff estimates the `num_buckets` by double addition instead of double
division. Specifically, in each `Add()`, we add `bucket_per_key_`
(inverse of `util_ratio_`) to the current `estimiated_num_buckets_`. The cost is
that we are gonna have the `estimated_num_buckets_` stored as one extra field
in the DataBlockHashIndexBuilder.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4293
Differential Revision: D9412472
Pulled By: fgwu
fbshipit-source-id: 2925c8509a401e7bd3c1ab1d9e9c7244755c277a
Summary:
Suppress two CLANG analyze warnings. They don't seem to be real bugs
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4291
Differential Revision: D9407333
Pulled By: siying
fbshipit-source-id: 2ed63d88fa0b217fdccb1572d7508467c2203dc8
Summary:
Followup for #4266. There is one more place in **get_context.cc** where **MergeOperator::ShouldMerge** should be called with reversed list of operands.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4284
Differential Revision: D9380008
Pulled By: sagar0
fbshipit-source-id: 70ec26e607e5b88465e1acbdcd6c6171bd76b9f2
Summary:
Add `--data_block_index_type` and `--data_block_hash_table_util_ratio` option to `db_bench`.
`--data_block_index_type` can be either of `binary` (default) or `binary_and_hash`;
`--data_block_hash_table_util_ratio` will be a double. The default value is `0.75`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4281
Differential Revision: D9361476
Pulled By: fgwu
fbshipit-source-id: dc53e01acef9db81b9eec5e8a96f3bc8ed718c10
Summary:
Add hash index support to data blocks, which helps to reduce the CPU utilization of point-lookup operations. This feature is backward compatible with the data block created without the hash index. It is disabled by default unless `BlockBasedTableOptions::data_block_index_type` is set to `data_block_index_type = kDataBlockBinaryAndHash.`
The DB size would be bigger with the hash index option as a hash table is added at the end of each data block. If the hash utilization ratio is 1:1, the space overhead is one byte per key. The hash table utilization ratio is adjustable using `BlockBasedTableOptions::data_block_hash_table_util_ratio`. A lower utilization ratio will improve more on the point-lookup efficiency, but take more space too.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4174
Differential Revision: D8965914
Pulled By: fgwu
fbshipit-source-id: 1c6bae5d1fc39c80282d8890a72e9e67bc247198
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:
After refactoring in https://github.com/facebook/rocksdb/pull/4158 the properties block is written after the index block. This breaks the existing logic in estimating the index size in partitioned indexes. The patch fixes that by using the accurate index block size, which is available since by the time we write the properties block, the index block is already written.
The patch also fixes an issue in estimating the partition size with format_version=3 which was resulting into partitions smaller than the configured metadata_block_size.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4259
Differential Revision: D9274454
Pulled By: maysamyabandeh
fbshipit-source-id: c82d045505cca3e7ed1a44ee1eaa26e4f25a4272
Summary:
Given that index value is a BlockHandle, which is basically an <offset, size> pair we can apply delta encoding on the values. The first value at each index restart interval encoded the full BlockHandle but the rest encode only the size. Refer to IndexBlockIter::DecodeCurrentValue for the detail of the encoding. This reduces the index size which helps using the block cache more efficiently. The feature is enabled with using format_version 4.
The feature comes with a bit of cpu overhead which should be paid back by the higher cache hits due to smaller index block size.
Results with sysbench read-only using 4k blocks and using 16 index restart interval:
Format 2:
19585 rocksdb read-only range=100
Format 3:
19569 rocksdb read-only range=100
Format 4:
19352 rocksdb read-only range=100
Pull Request resolved: https://github.com/facebook/rocksdb/pull/3983
Differential Revision: D8361343
Pulled By: maysamyabandeh
fbshipit-source-id: f882ee082322acac32b0072e2bdbb0b5f854e651
Summary:
If jemalloc is disabled or the API is incorrectly referenced (jemalloc api on windows have a prefix je_) memory usage is incorrectly reported for all block sizes. This is because sizeof(char) is always 1. sizeof() is calculated at compile time and *(char*) is char. The patch uses the size of the slice to fix that.
Fixes#4245
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4246
Differential Revision: D9233958
Pulled By: maysamyabandeh
fbshipit-source-id: 9646933b24504e2814c7379f06a31148829c6b4e
Summary:
RocksDB used to store global_seqno in external SST files written by
SstFileWriter. During file ingestion, RocksDB uses `pwrite` to update the
`global_seqno`. Since random write is not supported in some non-POSIX compliant
file systems, external SST file ingestion is not supported on these file
systems. To address this limitation, we no longer update `global_seqno` during
file ingestion. Later RocksDB uses the MANIFEST and other information in table
properties to deduce global seqno for externally-ingested SST files.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4172
Differential Revision: D8961465
Pulled By: riversand963
fbshipit-source-id: 4382ec85270a96be5bc0cf33758ca2b167b05071
Summary:
Added DataBlockIndexType option in BlockBasedTableOptions.
```
enum DataBlockIndexType : char {
kDataBlockBinarySearch = 0, // traditional block type
kDataBlockHashIndex = 1, // additional hash index appended to the end.
};
```
The default type is the traditional binary seek option: `kDataBlockBinarySearch`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4150
Differential Revision: D8895958
Pulled By: fgwu
fbshipit-source-id: 480adef48104cf11d30db3bad9a73f98b4a80c10
Summary:
92ee3350e0 introduces an out-of-bound check in BlockBasedTableIterator::Valid(). However, this flag is not reset when re-seeking in backward direction. This caused the iterator to be invalide by mistake. Fix it by always resetting the out-of-bound flag in every seek.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4187
Differential Revision: D8996600
Pulled By: siying
fbshipit-source-id: b6235ea614f71381e50e7904c4fb036300604ac1
Summary:
The first step of the `DataBlockHashIndex` implementation. A string based hash table is implemented and unit-tested.
`DataBlockHashIndexBuilder`: `Add()` takes pairs of `<key, restart_index>`, and formats it into a string when `Finish()` is called.
`DataBlockHashIndex`: initialized by the formatted string, and can interpret it as a hash table. Lookup for a key is supported by iterator operation.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4139
Reviewed By: sagar0
Differential Revision: D8866764
Pulled By: fgwu
fbshipit-source-id: 7f015f0098632c65979a22898a50424384730b10
Summary:
Currently in `Version::Get` when reporting ticker stats stored in `GetContext`, there is a big for-loop through all `Ticker` which adds unnecessary cost to overall CPU usage. We can optimize by storing only ticker values that are used in `Get()` calls in a new struct `GetContextStats` since only a small fraction of all tickers are used in `Get()` calls. For comparison, with the new approach we only need to visit 17 values while old approach will require visiting 100+ `Ticker`
Pull Request resolved: https://github.com/facebook/rocksdb/pull/3490
Differential Revision: D6969154
Pulled By: miasantreble
fbshipit-source-id: fc27072965a3a94125a3e6883d20dafcf5b84029
Summary:
Lint is not happy with some new code recently committed. Format them.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4161
Differential Revision: D8940582
Pulled By: siying
fbshipit-source-id: c9b43b1ef8c88b5e923911058b44eb77234b36b7
Summary:
Right now we use one hard-coded prefetch size to prefetch data from the tail of the SST files. However, this may introduce a waste for some use cases, while not efficient for others.
Introduce a way to adjust this prefetch size by tracking 32 recent times, and pick a value with which the wasted read is less than 10%
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4156
Differential Revision: D8916847
Pulled By: siying
fbshipit-source-id: 8413f9eb3987e0033ed0bd910f83fc2eeaaf5758
Summary:
The properties meta-block should come at the end since we always need to
read it when opening a file, unlike index/filter/other meta-blocks, which
are sometimes read depending on the user's configuration. This ordering
will allow us to (in a future PR) do a small readahead on the end of the file
to read properties and meta-index blocks with one I/O.
The bulk of this PR is a refactoring of the `BlockBasedTableBuilder::Finish`
function. It was previously too large with inconsistent error handling, which
made it difficult to change. So I broke it up into one function per meta-block
write, and tried to make error handling consistent within those functions.
Then reordering the metablocks was trivial -- just reorder the calls to these
helper functions.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4158
Differential Revision: D8921705
Pulled By: ajkr
fbshipit-source-id: 96c9cc3182eb1adf11af46adab79dbeba7b12fcc
Summary:
In all cases during `BlockBasedTable::Open`, we issue at least three read requests to the file's tail: (1) footer, (2) metaindex block, and (3) properties block. Depending on the config, we may also read other metablocks like filter and index.
This PR issues smaller readahead when we expect to do only the three necessary reads mentioned above. Then, 4KB should be enough (ignoring the case where there are lots of user-defined properties). We can keep doing 512KB readahead when additional reads are expected.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4159
Differential Revision: D8924002
Pulled By: ajkr
fbshipit-source-id: cfc713275de4d05ce11f18571f1d72e27ccd3356
Summary:
Refactor IndexBlockIter to reduce conditional branches on key_includes_seq_. IndexBlockIter::Prev is also separated from DataBlockIter::Prev, not to cache the prev entries as they are of less importance when iterating over the index block.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4141
Differential Revision: D8866437
Pulled By: maysamyabandeh
fbshipit-source-id: fdac76880426fc2be7d3c6354c09ab98f6657d4b
Summary:
Some logic only related to IndexBlockIter is separated from BlockIter to IndexBlockIter. This is done by writing an exclusive Seek() and SeekForPrev() for DataBlockIter, and all metadata block iter and tombstone block iter now use data block iter. Dealing with the BinarySeek() sharing problem by passing in the comparator to use.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4136
Reviewed By: maysamyabandeh
Differential Revision: D8859673
Pulled By: siying
fbshipit-source-id: 703e5e6824b82b7cbf4721f3594b94127797ca9e
Summary:
Fixes#3391.
This change adds a `DeleteRange` method to `SstFileWriter` and adds
support for ingesting SSTs with range deletion tombstones. This is
important for applications that need to atomically ingest SSTs while
clearing out any existing keys in a given key range.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/3778
Differential Revision: D8821836
Pulled By: anand1976
fbshipit-source-id: ca7786c1947ff129afa703dab011d524c7883844
Summary:
The patch makes sure that two parallel test threads will operate on different db paths. This enables using open source tools such as gtest-parallel to run the tests of a file in parallel.
Example: ``` ~/gtest-parallel/gtest-parallel ./table_test```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4135
Differential Revision: D8846653
Pulled By: maysamyabandeh
fbshipit-source-id: 799bad1abb260e3d346bcb680d2ae207a852ba84
Summary:
- Avoid `strdup` to use jemalloc on Windows
- Use `size_t` for consistency
- Add GCC 8 to Travis
- Add CMAKE_BUILD_TYPE=Release to Travis
Pull Request resolved: https://github.com/facebook/rocksdb/pull/3433
Differential Revision: D6837948
Pulled By: sagar0
fbshipit-source-id: b8543c3a4da9cd07ee9a33f9f4623188e233261f
Summary:
BlockIter is getting crowded including details that specific only to either index or data blocks. The patch moves down such details to DataBlockIter and IndexBlockIter, both inheriting from BlockIter.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4121
Differential Revision: D8816832
Pulled By: maysamyabandeh
fbshipit-source-id: d492e74155c11d8a0c1c85cd7ee33d24c7456197
Summary:
Run the basic range deletion tests against the standard set of
configurations. This testing exposed that files with hash indexes and
partitioned indexes were not handling the case where the file contained
only range deletions--i.e., where the index was empty.
Additionally file a TODO about the fact that range deletions are broken
when allow_mmap_reads = true is set.
/cc ajkr nvanbenschoten
Best viewed with ?w=1: https://github.com/facebook/rocksdb/pull/4021/files?w=1
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4021
Differential Revision: D8811860
Pulled By: ajkr
fbshipit-source-id: 3cc07e6d6210a2a00b932866481b3d5c59775343
Summary:
This was caught by crash test, and the following is a simple way to reproduce it and verify the fix.
One way to trigger this code path is to use the following configuration:
- Compress SST file
- Enable direct IO and prefetch buffer
- Do NOT use compressed block cache
Closes https://github.com/facebook/rocksdb/pull/4096
Differential Revision: D8742009
Pulled By: riversand963
fbshipit-source-id: f13381078bbb0dce92f60bd313a78ab602bcacd2
Summary:
Increase the size of each shard so that the number of cache hit/miss match
expectation. Otherwise FilterBlockInBlockCache test will fail.
Closes https://github.com/facebook/rocksdb/pull/4090
Differential Revision: D8736158
Pulled By: riversand963
fbshipit-source-id: 5cdbc06b02390389fd5b72a6d251d88949ad3d91
Summary:
We can have prefetch_index without prefetch_filter but not the other way around. The assert statement is fixed.
Closes https://github.com/facebook/rocksdb/pull/4077
Differential Revision: D8694472
Pulled By: maysamyabandeh
fbshipit-source-id: ccd2804d9d9cdafb1c3e65062c7bc38603e69004
Summary:
Currently the block cache is charged only by the size of the raw data block and excludes the overhead of the c++ objects that contain the raw data block. The patch improves the accuracy of the charge by including the c++ object overhead into it.
Closes https://github.com/facebook/rocksdb/pull/4073
Differential Revision: D8686552
Pulled By: maysamyabandeh
fbshipit-source-id: 8472f7fc163c0644533bc6942e20cdd5725f520f
Summary:
with https://github.com/facebook/rocksdb/pull/3601 and https://github.com/facebook/rocksdb/pull/3899, `prefix_extractor_` is not really being used in block based filter and full filter's version of `PrefixMayMatch` because now `prefix_extractor` is passed as an argument. Also it is now possible that prefix_extractor_ may be initialized to nullptr when a non-standard prefix_extractor is used and also for ROCKSDB_LITE. Removing these checks should not break any existing tests.
Closes https://github.com/facebook/rocksdb/pull/4067
Differential Revision: D8669002
Pulled By: miasantreble
fbshipit-source-id: 0e701ba912b8a26734fadb72d15bb1b266b6176a
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:
https://github.com/facebook/rocksdb/pull/3881 fixed a bug where PinnableSlice pin mmap files which could be deleted with background compaction. This is however a non-issue for ReadOnlyDB when there is no compaction running and max_open_files is -1. This patch reenables the pinning feature for that case.
Closes https://github.com/facebook/rocksdb/pull/4053
Differential Revision: D8662546
Pulled By: maysamyabandeh
fbshipit-source-id: 402962602eb0f644e17822748332999c3af029fd
Summary:
This is implemented by extending ReadCallback with another function `MaxUnpreparedSequenceNumber` which returns the largest visible sequence number for the current transaction, if there is uncommitted data written to DB. Otherwise, it returns zero, indicating no uncommitted data.
There are the places where reads had to be modified.
- Get and Seek/Next was just updated to seek to max(snapshot_seq, MaxUnpreparedSequenceNumber()) instead, and iterate until a key was visible.
- Prev did not need need updates since it did not use the Seek to sequence number optimization. Assuming that locks were held when writing unprepared keys, and ValidateSnapshot runs, there should only be committed keys and unprepared keys of the current transaction, all of which are visible. Prev will simply iterate to get the last visible key.
- Reseeking to skip keys optimization was also disabled for write unprepared, since it's possible to hit the max_skip condition even while reseeking. There needs to be some way to resolve infinite looping in this case.
Closes https://github.com/facebook/rocksdb/pull/3955
Differential Revision: D8286688
Pulled By: lth
fbshipit-source-id: 25e42f47fdeb5f7accea0f4fd350ef35198caafe
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:
Previously in https://github.com/facebook/rocksdb/pull/3601 bloom filter will only be checked if `prefix_extractor` in the mutable_cf_options matches the one found in the SST file.
This PR relaxes the requirement by checking if all keys in the range [user_key, iterate_upper_bound) all share the same prefix after transforming using the BF in the SST file. If so, the bloom filter is considered compatible and will continue to be looked at.
Closes https://github.com/facebook/rocksdb/pull/3899
Differential Revision: D8157459
Pulled By: miasantreble
fbshipit-source-id: 18d17cba56a1005162f8d5db7a27aba277089c41
Summary:
Pass in `for_compaction` to `BlockBasedTableIterator` via `BlockBasedTableReader::NewIterator`.
In 7103559f49, `for_compaction` was set in `BlockBasedTable::Rep` via `BlockBasedTable::SetupForCompaction`. In hindsight it was not the right decision; it also caused TSAN to complain.
Closes https://github.com/facebook/rocksdb/pull/4048
Differential Revision: D8601056
Pulled By: sagar0
fbshipit-source-id: 30127e898c15c38c1080d57710b8c5a6d64a0ab3
Summary:
Top-level index in partitioned index/filter blocks are small and could be pinned in memory. So far we use that by cache_index_and_filter_blocks to false. This however make it difficult to keep account of the total memory usage. This patch introduces pin_top_level_index_and_filter which in combination with cache_index_and_filter_blocks=true keeps the top-level index in cache and yet pinned them to avoid cache misses and also cache lookup overhead.
Closes https://github.com/facebook/rocksdb/pull/4037
Differential Revision: D8596218
Pulled By: maysamyabandeh
fbshipit-source-id: 3a5f7f9ca6b4b525b03ff6bd82354881ae974ad2
Summary:
This PR extends the improvements in #3282 to also work when using Direct IO.
We see **4.5X performance improvement** in seekrandom benchmark doing long range scans, when using direct reads, on flash.
**Description:**
This change improves the performance of iterators doing long range scans (e.g. big/full index or table scans in MyRocks) by using readahead and prefetching additional data on each disk IO, and storing in a local buffer. This prefetching is automatically enabled on noticing more than 2 IOs for the same table file during iteration. The readahead size starts with 8KB and is exponentially increased on each additional sequential IO, up to a max of 256 KB. This helps in cutting down the number of IOs needed to complete the range scan.
**Implementation Details:**
- Used `FilePrefetchBuffer` as the underlying buffer to store the readahead data. `FilePrefetchBuffer` can now take file_reader, readahead_size and max_readahead_size as input to the constructor, and automatically do readahead.
- `FilePrefetchBuffer::TryReadFromCache` can now call `FilePrefetchBuffer::Prefetch` if readahead is enabled.
- `AlignedBuffer` (which is the underlying store for `FilePrefetchBuffer`) now takes a few additional args in `AlignedBuffer::AllocateNewBuffer` to allow copying data from the old buffer.
- Made sure not to re-read partial chunks of data that were already available in the buffer, from device again.
- Fixed a couple of cases where `AlignedBuffer::cursize_` was not being properly kept up-to-date.
**Constraints:**
- Similar to #3282, this gets currently enabled only when ReadOptions.readahead_size = 0 (which is the default value).
- Since the prefetched data is stored in a temporary buffer allocated on heap, this could increase the memory usage if you have many iterators doing long range scans simultaneously.
- Enabled only for user reads, and disabled for compactions. Compaction reads are controlled by the options `use_direct_io_for_flush_and_compaction` and `compaction_readahead_size`, and the current feature takes precautions not to mess with them.
**Benchmarks:**
I used the same benchmark as used in #3282.
Data fill:
```
TEST_TMPDIR=/data/users/$USER/benchmarks/iter ./db_bench -benchmarks=fillrandom -num=1000000000 -compression_type="none" -level_compaction_dynamic_level_bytes
```
Do a long range scan: Seekrandom with large number of nexts
```
TEST_TMPDIR=/data/users/$USER/benchmarks/iter ./db_bench -benchmarks=seekrandom -use_direct_reads -duration=60 -num=1000000000 -use_existing_db -seek_nexts=10000 -statistics -histogram
```
```
Before:
seekrandom : 37939.906 micros/op 26 ops/sec; 29.2 MB/s (1636 of 1999 found)
With this change:
seekrandom : 8527.720 micros/op 117 ops/sec; 129.7 MB/s (6530 of 7999 found)
```
~4.5X perf improvement. Taken on an average of 3 runs.
Closes https://github.com/facebook/rocksdb/pull/3884
Differential Revision: D8082143
Pulled By: sagar0
fbshipit-source-id: 4d7a8561cbac03478663713df4d31ad2620253bb
Summary:
https://github.com/facebook/rocksdb/pull/3764 introduced an optimization feature to skip duplicate prefix entires in full bloom filters. Unfortunately it also introduces a bug in partitioned full filters, where the duplicate prefix should still be inserted if it is in a new partition. The patch fixes the bug by resetting the duplicate detection logic each time a partition is cut.
This bug could result into false negatives, which means that DB could skip an existing key.
Closes https://github.com/facebook/rocksdb/pull/4024
Differential Revision: D8518866
Pulled By: maysamyabandeh
fbshipit-source-id: 044f4d988e606a330ecafd8c79daceb68b8796bf
Summary:
b555ed30a4 makes the BlockBasedTableIterator to be invalidated if the current position if over the upper bound. However, this can bring performance regression to the case of multiple Seek()s hitting the same data block but all out of upper bound.
For example, if an SST file has a data block containing following keys : {a, z}
The user sets the upper bound to be "x", and it executed following queries:
Seek("b")
Seek("c")
Seek("d")
Before the upper bound optimization, these queries always come to this same current data block of the iterator, but now inside each Seek() the data block is read from the block cache but is returned again.
To prevent this regression case, we keep the current data block iterator if it is upper bound.
Closes https://github.com/facebook/rocksdb/pull/4004
Differential Revision: D8463192
Pulled By: siying
fbshipit-source-id: 8710628b30acde7063a097c3184d6c4333a8ef81
Summary:
The Block object assumes contents are uncompressed. Block's constructor tries to read the number of restarts, but does not get an accurate number when its contents are compressed, which is causing issues like https://github.com/facebook/rocksdb/issues/3843.
This PR address this issue by skipping reconstruction of restart points when blocks are known to be compressed. Somehow the restart points can be read directly when Snappy is used and some tests (for example https://github.com/facebook/rocksdb/blob/master/db/db_block_cache_test.cc#L196) expects blocks to be fully constructed even when Snappy compression is used, so here we keep the restart point logic for Snappy.
Closes https://github.com/facebook/rocksdb/pull/3996
Differential Revision: D8416186
Pulled By: miasantreble
fbshipit-source-id: 002c0b62b9e5d89fb7736563d354ce0023c8cb28
Summary:
A recent change pushed down the upper bound checking to child iterators. However, this causes the logic of following sequence wrong:
Seek(key);
if (!Valid()) SeekToLast();
Because !Valid() may be caused by upper bounds, rather than the end of the iterator. In this case SeekToLast() points to totally wrong places. This can cause wrong results, infinite loops, or segfault in some cases.
This sequence is called when changing direction from forward to backward. And this by itself also implicitly happen during reseeking optimization in Prev().
Fix this bug by using SeekForPrev() rather than this sequuence, as what is already done in prefix extrator case.
Closes https://github.com/facebook/rocksdb/pull/3989
Differential Revision: D8385422
Pulled By: siying
fbshipit-source-id: 429e869990cfd2dc389421e0836fc496bed67bb4
