Summary:
The current implementation of a binary heap in `util/heap.h` does a move-assign in the `pop` method. In the case that there is exactly one element stored in the heap, this ends up being a self-move-assign. This can cause trouble with certain classes, which are not prepared for this. Furthermore, it trips up the glibc STL debugger (`-D_GLIBCXX_DEBUG`), which produces an assertion failure in this case.
This PR addresses this problem by not doing the (unnecessary in this case) move-assign if there is only one element in the heap.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7942
Reviewed By: jay-zhuang
Differential Revision: D26528739
Pulled By: ajkr
fbshipit-source-id: 5ca570e0c4168f086b10308ad766dff84e6e2d03
Summary:
When dynamically linking two binaries together, different builds of RocksDB from two sources might cause errors. To provide a tool for user to solve the problem, the RocksDB namespace is changed to a flag which can be overridden in build time.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6433
Test Plan: Build release, all and jtest. Try to build with ROCKSDB_NAMESPACE with another flag.
Differential Revision: D19977691
fbshipit-source-id: aa7f2d0972e1c31d75339ac48478f34f6cfcfb3e
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:
Removed `one_time_use` flag, which removed the need for some
tests, and changed all `NewRangeTombstoneIterator` methods to return
`FragmentedRangeTombstoneIterators`.
These changes also led to removing `RangeDelAggregatorV2::AddUnfragmentedTombstones`
and one of the `MemTableListVersion::AddRangeTombstoneIterators` methods.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4692
Differential Revision: D13106570
Pulled By: abhimadan
fbshipit-source-id: cbab5432d7fc2d9cdfd8d9d40361a1bffaa8f845
Summary:
Previously, every range tombstone iterator was seeked on every
ShouldDelete call, which quickly degraded performance for long range
scans. This PR improves performance by tracking iterator positions and
only advancing iterators when necessary.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4677
Differential Revision: D13205373
Pulled By: abhimadan
fbshipit-source-id: 80c199dace1e19362a4c61c686bf01913eae87cb
Summary:
Reduce number of comparisons in heap by caching which child node in the first level is smallest (left_child or right_child)
So next time we can compare directly against the smallest child
I see that the total number of calls to comparator drops significantly when using this optimization
Before caching (~2mil key comparison for iterating the DB)
```
$ DEBUG_LEVEL=0 make db_bench -j64 && ./db_bench --benchmarks="readseq" --db="/dev/shm/heap_opt" --use_existing_db --disable_auto_compactions --cache_size=1000000000 --perf_level=2
readseq : 0.338 micros/op 2959201 ops/sec; 327.4 MB/s user_key_comparison_count = 2000008
```
After caching (~1mil key comparison for iterating the DB)
```
$ DEBUG_LEVEL=0 make db_bench -j64 && ./db_bench --benchmarks="readseq" --db="/dev/shm/heap_opt" --use_existing_db --disable_auto_compactions --cache_size=1000000000 --perf_level=2
readseq : 0.309 micros/op 3236801 ops/sec; 358.1 MB/s user_key_comparison_count = 1000011
```
It also improves
Closes https://github.com/facebook/rocksdb/pull/1600
Differential Revision: D4256027
Pulled By: IslamAbdelRahman
fbshipit-source-id: 76fcc66
Summary:
While profiling compaction in our service I noticed a lot of CPU (~15% of compaction) being spent in MergingIterator and key comparison. Looking at the code I found MergingIterator was (understandably) using std::priority_queue for the multiway merge.
Keys in our dataset include sequence numbers that increase with time. Adjacent keys in an L0 file are very likely to be adjacent in the full database. Consequently, compaction will often pick a chunk of rows from the same L0 file before switching to another one. It would be great to avoid the O(log K) operation per row while compacting.
This diff replaces std::priority_queue with a custom binary heap implementation. It has a "replace top" operation that is cheap when the new top is the same as the old one (i.e. the priority of the top entry is decreased but it still stays on top).
Test Plan:
make check
To test the effect on performance, I generated databases with data patterns that mimic what I describe in the summary (rows have a mostly increasing sequence number). I see a 10-15% CPU decrease for compaction (and a matching throughput improvement on tmpfs). The exact improvement depends on the number of L0 files and the amount of locality. Performance on randomly distributed keys seems on par with the old code.
Reviewers: kailiu, sdong, igor
Reviewed By: igor
Subscribers: yoshinorim, dhruba, tnovak
Differential Revision: https://reviews.facebook.net/D29133
Max Neunhoeffer