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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2710) disable dynamic like optimization for collated databases
Date Tue, 29 May 2007 06:32:16 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2710?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12499692

Mamta A. Satoor commented on DERBY-2710:

The collation rule for c1 like c2 should be same as c1 = c2 as per SQL specification. 

As per SQL spec, Section 8.5 <like predicate>, Syntax Rules 3d), 
"The collation used for <like predicate> is determined by applying Subclause 9.13, "Collation
determination", with operands CVE, PC, and (if specified) EC."

As per SQL spec, Section 8.2 <comparison predicate>, General Rules 3a),
"Let CS be the collation as determined by Subclause 9.13, "Collation determination", for the
declared types of the two character strings."

Please let me know if you have any further questions in this area.

> disable dynamic like optimization for collated databases
> --------------------------------------------------------
>                 Key: DERBY-2710
>                 URL: https://issues.apache.org/jira/browse/DERBY-2710
>             Project: Derby
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions:
>            Reporter: Mike Matrigali
>            Assignee: Mike Matrigali
> I think Code needs to be added to opensource/java/engine/org/apache/derby/impl/sql/compile/LikeEscapeOperatorNode.java
> to disable like optimization for databases with non-default collation.  There is left
over code in this routine that says it disables it for national char by adding a cast to one
of the two sides which I assume then stops some other code from considering the 
> optimization.

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