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From "A B (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-2503) Implement IN-list multi-probing logic for hash joins.
Date Thu, 29 Mar 2007 23:27:25 GMT
Implement IN-list multi-probing logic for hash joins.
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                 Key: DERBY-2503
                 URL: https://issues.apache.org/jira/browse/DERBY-2503
             Project: Derby
          Issue Type: Improvement
          Components: Performance
    Affects Versions: 10.3.0.0
            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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