199fabc197
Summary: Commit of delayed prepared has two non-atomic steps: add to commit cache, remove from delayed_prepared_. Similarly in ::IsInSnapshot we read from commit cache first and then look into delayed_prepared_. Due to non-atomicity thus the reader might not find the prep_seq that is just committed neither in commit cache nor in delayed_prepared_. To fix that i) we check if there was any delayed prepared BEFORE looking into commit cache, ii) if there was, we complete the search steps to be these: i) commit cache, ii) delayed prepared, commit cache again. In this way if the first query to commit cache missed the commit, the 2nd will catch it. The cost of the redundant read from commit cache is paid only if delayed_prepared_ is nonempty which should be a very rare scenario. Pull Request resolved: https://github.com/facebook/rocksdb/pull/4947 Differential Revision: D13952754 Pulled By: maysamyabandeh fbshipit-source-id: 8f47826b13f8ce154398d842028342423f4ca2b2
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.