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https://issues.apache.org/jira/browse/FLINK-9070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16470004#comment-16470004
]
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]
>
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