78e291b17e
Summary: The patch cleans up the code and improves the consistency checks around adding/deleting table files in `VersionBuilder`. Namely, it makes the checks stricter and improves them in the following ways: 1) A table file can now only be deleted from the LSM tree using the level it resides on. Earlier, there was some unnecessary wiggle room for trivially moved files (they could be deleted using a lower level number than the actual one). 2) A table file cannot be added to the tree if it is already present in the tree on any level (not just the target level). The earlier code only had an assertion (which is a no-op in release builds) that the newly added file is not already present on the target level. 3) The above consistency checks around state transitions are now mandatory, as opposed to the earlier `CheckConsistencyForDeletes`, which was a no-op in release mode unless `force_consistency_checks` was set to `true`. The rationale here is that assuming that the initial state is consistent, a valid transition leads to a next state that is also consistent; however, an *invalid* transition offers no such guarantee. Hence it makes sense to validate the transitions unconditionally, and save `force_consistency_checks` for the paranoid checks that re-validate the entire state. 4) The new checks build on the mechanism introduced in https://github.com/facebook/rocksdb/pull/6862, which enables us to efficiently look up the location (level and position within level) of files in a `Version` by file number. This makes the consistency checks much more efficient than the earlier `CheckConsistencyForDeletes`, which essentially performed a linear search. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6901 Test Plan: Extended the unit tests and ran: `make check` `make whitebox_crash_test` Reviewed By: ajkr Differential Revision: D21822714 Pulled By: ltamasi fbshipit-source-id: e2b29c8b6da1bf0f59004acc889e4870b2d18215 |
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README.md
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.
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/ and https://rocksdb.slack.com/
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.