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https://issues.apache.org/jira/browse/DERBY-6226?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13666431#comment-13666431
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Tony Brusseau commented on DERBY-6226:
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I think for the cases that can easily be handled as a union, one might want to
consider parallelizing the query satisfaction. I don't know, maybe you do this
already for unions 8-). Also since all of these will have the same FROM clause,
any subselects in there should only be evaluated once.
> enhance optmizer to use multiple probes into multiple indexes to satisfy OR
> queries on different columns.
> ---------------------------------------------------------------------------------------------------------
>
> Key: DERBY-6226
> URL: https://issues.apache.org/jira/browse/DERBY-6226
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 10.8.3.1, 10.11.0.0
> Reporter: Mike Matrigali
>
> For queries of the type:
> select * from a where col1 = ? or col2 = ?
> and good indexes exist on col1 and col2 it would optimal if derby could
> execute a plan that
> did an index scan first on the col1 index and then an index scan on col2
> index.
> Currently it looks like derby will do a full index scan if col1 and col2 are
> in any index, or a full table
> scan otherwise.
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