5508122ed6
Summary: I noticed that memtable iterator usually crosses the `iterate_upper_bound` threshold when tailing. Changes introduced in D43833 made `NeedToSeekImmutable` always return true in such case, even when `Seek()` only needs to rewind the memtable iterator. In a test I ran, this caused the "tailing efficiency" (ratio of calls to `Seek()` that only affect the memtable versus all seeks) to drop almost to zero. This diff attempts to fix the regression by using a different flag to indicate that `current_` is over the limit instead of resetting `valid_` in `UpdateCurrent()`. Test Plan: `DBTestTailingIterator.TailingIteratorUpperBound` Reviewers: sdong, rven Reviewed By: rven Subscribers: dhruba, march Differential Revision: https://reviews.facebook.net/D45909
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/