1e35584251
Summary: Currently, when the block cache is used for index blocks as well, it is not really the index block that is stored in the cache but an IndexReader object. Since this object is not pure data (it has, for instance, pointers that might dangle), it's not really sharable. To avoid the issues around this, the current code uses a dummy unique cache key for each TableReader to store the IndexReader, and erases the IndexReader entry when the TableReader is closed. Instead of doing this, the new code moves the IndexReader out of the cache altogether. In particular, instead of the TableReader owning, or caching/pinning the IndexReader based on the customer's settings, the TableReader unconditionally owns the IndexReader, which in turn owns/caches/pins the index block (which is itself sharable and thus can be safely put in the cache without any hacks). Note: the change has two side effects: 1) Partitions of partitioned indexes no longer affect the read amplification statistics. 2) Eviction statistics for index blocks are temporarily broken. We plan to fix this in a separate phase. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5298 Differential Revision: D15303203 Pulled By: ltamasi fbshipit-source-id: 935a69ba59d87d5e44f42e2310619b790c366e47
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 specially 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/
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.