3ea1ec56df
Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/15321 `MultiGet` with `read_tier = kBlockCacheTier` now returns `Incomplete` for data blocks that are not in the block cache. Before this fix, it read them from disk. **Why it matters:** Callers use `kBlockCacheTier` to prevent disk I/O. `Get` obeyed it, but `MultiGet` did not. **Problem** - Without mmap reads, `MultiGet` sends cache misses to `RetrieveMultipleBlocks`. - That path called `MultiRead` with no `kBlockCacheTier` check. - `RetrieveBlock` (used by `Get`) has the check. **Fix** - `RetrieveMultipleBlocks`: if `read_tier == kBlockCacheTier`, set `Incomplete("no blocking io")` for each block and do no I/O. - `MultiGet`: when a block is `Incomplete`, return that status for the key, the same as `Get`. Before, the key status stayed `OK` with no value. - Release note in `unreleased_history/bug_fixes`. **Tests** - New `DBTest2.MultiGetBlockCacheTierSkipsColdSstData`: `Get` and `MultiGet` both return `Incomplete` for a key whose data block is not in the cache. - `DBBlobBasicTest.MultiGetBlobsFromCache` relied on the bug. Its inline key passed only because `MultiGet` read the data block from disk. The test now loads the block cache first, so it still checks the blob cache. Reviewed By: joshkang97 Differential Revision: D122431823 fbshipit-source-id: 262913930cb4b570ea0a4d8f4f92364de08a27f5
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/main/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.
Questions and discussions are welcome on the RocksDB Developers Public Facebook group and email list on Google Groups.
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.