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https://issues.apache.org/jira/browse/DERBY-2503?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dag H. Wanvik updated DERBY-2503:
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Derby Categories: [Performance]
> Implement IN-list multi-probing logic for hash joins.
> -----------------------------------------------------
>
> Key: DERBY-2503
> URL: https://issues.apache.org/jira/browse/DERBY-2503
> Project: Derby
> Issue Type: Improvement
> Affects Versions: 10.3.1.4
> Reporter: A B
> Priority: Minor
>
> DERBY-47 added a new MultiProbeTableScanResult to handle multi-probing for
> nested loop joins, which leads to significant performance improvements for
> certain IN-list queries. However, that Jira did not extend the multi-probing
> functionality to hash joins. As a result, queries for which the optimizer
> chooses to do hash joins cannot currently reap the benefits of IN-list
> multi-probing (see DERBY-2500).
> It would be good to enhance Derby's execution-time handling of
> HashScanResultSets so that it can take advantage of IN-list multi-probing for
> hash joins, as well. Doing so would allow Derby to read fewer rows from disk
> (similar to DERBY-47) and would also have the convenient side-effect of
> decreasing the size of the in-memory hash table.
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