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https://issues.apache.org/jira/browse/FLINK-14997?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stephan Ewen closed FLINK-14997.
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> Avoid to call unnecessary delete within RocksDBState's mergeNamespaces
> implementation
> -------------------------------------------------------------------------------------
>
> Key: FLINK-14997
> URL: https://issues.apache.org/jira/browse/FLINK-14997
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / State Backends
> Reporter: Yun Tang
> Assignee: Yun Tang
> Priority: Minor
> Labels: pull-request-available
> Fix For: 1.10.0
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> After FLINK-7700, we delete old state when merging namespaces of RocksDB
> state. However, this change still leaves some performance space to improve:
> {code:java}
> byte[] valueBytes = backend.db.get(columnFamily, sourceKey);
> backend.db.delete(columnFamily, writeOptions, sourceKey);
> if (valueBytes != null) {
> backend.db.merge(columnFamily, writeOptions, targetKey, valueBytes);
> }
> {code}
> As you can see, we would call delete instantly after we get the
> {{valueBytes}}. However, since we did not allow {{null}} in list state value
> and the delete operation could be removed to the statement block which has
> verified the {{valueBytes}} is not null. By doing this, we could avoid
> unnecessary {{delete}} calls if {{sourceKey}} not existed actually.
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