Summary:
The compaction will incorrectly drop a key under the following conditions:
1. Open an empty database.
2. Use the `IngestExternalFile` API to ingest an SST file (the global sequence number will be 0).
3. Create a snapshot (the snapshot sequence number will be 0).
4. Trigger compaction; the key in the above SST file will be dropped.
The drop condition is found here: f20d12adc8/db/compaction/compaction_iterator.cc (L875-L878)
The condition does not explicitly check if a previous key exists.
Fix: Add a check of `last_sequence != kMaxSequenceNumber` to verify if there is a previous key
Pull Request resolved: https://github.com/facebook/rocksdb/pull/13155
Reviewed By: jowlyzhang
Differential Revision: D66473015
Pulled By: cbi42
fbshipit-source-id: 93a3ec5c103f95e9bb97e3944ba6e752a5394421
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.
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.
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.
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