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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-2503) Implement IN-list multi-probing logic for hash joins.
Date Mon, 29 Jun 2009 14:11:47 GMT

     [ https://issues.apache.org/jira/browse/DERBY-2503?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Dag H. Wanvik updated DERBY-2503:

    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:
>            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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