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ASF GitHub Bot commented on FLINK-9070: --------------------------------------- Github user bowenli86 commented on a diff in the pull request: https://github.com/apache/flink/pull/5979#discussion_r187255609 --- Diff: flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBMapState.java --- @@ -356,6 +369,20 @@ private UV deserializeUserValue(byte[] rawValueBytes, TypeSerializer<UV> valueSe return isNull ? null : valueSerializer.deserialize(in); } + private boolean startWithKeyPrefix(byte[] keyPrefixBytes, byte[] rawKeyBytes) { + if (rawKeyBytes.length < keyPrefixBytes.length) { + return false; + } + + for (int i = keyPrefixBytes.length; --i >= backend.getKeyGroupPrefixBytes(); ) { --- End diff -- I recommend moving `--i` to the increment part of the `for` loop, instead of keeping it in the termination part > Improve performance of RocksDBMapState.clear() > ---------------------------------------------- > > Key: FLINK-9070 > URL: https://issues.apache.org/jira/browse/FLINK-9070 > Project: Flink > Issue Type: Improvement > Components: State Backends, Checkpointing > Affects Versions: 1.6.0 > Reporter: Truong Duc Kien > Assignee: Sihua Zhou > Priority: Major > Fix For: 1.6.0 > > > Currently, RocksDBMapState.clear() is implemented by iterating over all the > keys and drop them one by one. This iteration can be quite slow with: > * Large maps > * High-churn maps with a lot of tombstones > There are a few methods to speed-up deletion for a range of keys, each with > their own caveats: > * DeleteRange: still experimental, likely buggy > * DeleteFilesInRange + CompactRange: only good for large ranges > > Flink can also keep a list of inserted keys in-memory, then directly delete > them without having to iterate over the Rocksdb database again. > > Reference: > * [RocksDB article about range > deletion|https://github.com/facebook/rocksdb/wiki/Delete-A-Range-Of-Keys] > * [Bug in DeleteRange|https://pingcap.com/blog/2017-09-08-rocksdbbug] > -- This message was sent by Atlassian JIRA (v7.6.3#76005)