f622ca2c7c
Summary: Add savepoint support when the current transaction has flushed unprepared batches. Rolling back to savepoint is similar to rolling back a transaction. It requires the set of keys that have changed since the savepoint, re-reading the keys at the snapshot at that savepoint, and the restoring the old keys by writing out another unprepared batch. For this strategy to work though, we must be capable of reading keys at a savepoint. This does not work if keys were written out using the same sequence number before and after a savepoint. Therefore, when we flush out unprepared batches, we must split the batch by savepoint if any savepoints exist. eg. If we have the following: ``` Put(A) Put(B) Put(C) SetSavePoint() Put(D) Put(E) SetSavePoint() Put(F) ``` Then we will write out 3 separate unprepared batches: ``` Put(A) 1 Put(B) 1 Put(C) 1 Put(D) 2 Put(E) 2 Put(F) 3 ``` This is so that when we rollback to eg. the first savepoint, we can just read keys at snapshot_seq = 1. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5627 Differential Revision: D16584130 Pulled By: lth fbshipit-source-id: 6d100dd548fb20c4b76661bd0f8a2647e64477fa
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.