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https://issues.apache.org/jira/browse/DERBY-4346?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mamta A. Satoor updated DERBY-4346:
-----------------------------------
Urgency: Normal
Labels: derby_triage10_10 (was: )
> LIKE with parameter recomputes greaterEqualString and lessThanString way too
> often
> ----------------------------------------------------------------------------------
>
> Key: DERBY-4346
> URL: https://issues.apache.org/jira/browse/DERBY-4346
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 10.5.1.1
> Reporter: Knut Anders Hatlen
> Labels: derby_triage10_10
>
> I profiled a 7-way join (the exact query can be found here:
> http://src.opensolaris.org/source/xref/opengrok/trunk/src/org/opensolaris/opengrok/history/JDBCHistoryCache_queries.properties?r=809%3Abdef8b63f333#82
> ) and saw that 40% of the time was spent in
> Like.greaterEqualStringFromParameterWithEsc() and
> Like.lessThanStringFromParameterWithEsc().
> These methods are used to generate "x >= greaterEqualString" and "x <
> lessThanString" clauses that enable a "LIKE ?" clause to make use of indexes.
> Since the value of the ? parameter is constant throughout a single execution
> of the statement, it should only be necessary to invoke these methods once
> per LIKE clause per execution. They are clearly called more frequently for
> the query in question, and reducing the number of invocations to one per
> execution would probably make the query execute almost twice as fast.
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