643c863b72
Summary: PR https://github.com/facebook/rocksdb/issues/6944 transitioned `BlockIter` from using `Comparator*` to using concrete `UserComparatorWrapper` and `InternalKeyComparator`. However, adding them as instance variables to `BlockIter` was not optimal. Bloating `BlockIter` caused the `ArenaWrappedDBIter`'s arena allocator to do more heap allocations (in certain cases) which harmed performance of `DB::NewIterator()`. This PR pushes down the concrete comparator objects to the point of usage, which forces them to be on the stack. As a result, the `BlockIter` is back to its original size prior to https://github.com/facebook/rocksdb/issues/6944 (actually a bit smaller since there were two `Comparator*` before). Pull Request resolved: https://github.com/facebook/rocksdb/pull/7149 Test Plan: verified our internal `DB::NewIterator()`-heavy regression test no longer reports regression. Reviewed By: riversand963 Differential Revision: D22623189 Pulled By: ajkr fbshipit-source-id: f6d69accfe5de51e0bd9874a480b32b29909bab6
RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key-value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it especially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/master/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Design discussions are conducted in https://www.facebook.com/groups/rocksdb.dev/ and https://rocksdb.slack.com/
License
RocksDB is dual-licensed under both the GPLv2 (found in the COPYING file in the root directory) and Apache 2.0 License (found in the LICENSE.Apache file in the root directory). You may select, at your option, one of the above-listed licenses.