e4234fbdcf
Summary: In our testing cluster, we found large amount tombstone has been promoted to kValue type from kMerge after reaching the top level of compaction. Since we used to only collecting tombstone in merge operator, those tombstones can never be collected. This PR addresses the issue by adding a GC step in compaction filter, which is only for kValue type records. Since those record already reached the top of compaction (no earlier data exists) we can safely remove them in compaction filter without worrying old data appears. This PR also removes an old optimization in cassandra merge operator for single merge operands. We need to do GC even on a single operand, so the optimation does not make sense anymore. Closes https://github.com/facebook/rocksdb/pull/2855 Reviewed By: sagar0 Differential Revision: D5806445 Pulled By: wpc fbshipit-source-id: 6eb25629d4ce917eb5e8b489f64a6aa78c7d270b
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/