f32a572099
Summary: While working on supporting mixing merge operators with single deletes ( https://reviews.facebook.net/D43179 ), I realized that returning and dealing with merge results can be made simpler. Submitting this as a separate diff because it is not directly related to single deletes. Before, callers of merge helper had to retrieve the merge result in one of two ways depending on whether the merge was successful or not (success = result of merge was single kTypeValue). For successful merges, the caller could query the resulting key/value pair and for unsuccessful merges, the result could be retrieved in the form of two deques of keys and values. However, with single deletes, a successful merge does not return a single key/value pair (if merge operands are merged with a single delete, we have to generate a value and keep the original single delete around to make sure that we are not accidentially producing a key overwrite). In addition, the two existing call sites of the merge helper were taking the same actions independently from whether the merge was successful or not, so this patch simplifies that. Test Plan: make clean all check Reviewers: rven, sdong, yhchiang, anthony, igor Reviewed By: igor Subscribers: dhruba, leveldb Differential Revision: https://reviews.facebook.net/D43353
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/