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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3854) Implement LIKE transformations and optimizations for databases using territory-based collations
Date Fri, 29 Aug 2008 17:22:44 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3854?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12627040#action_12627040
] 

Rick Hillegas commented on DERBY-3854:
--------------------------------------

Hi Knut,

This looks like a promising approach. It certainly seems that we ought to be able to find
a longest, well-behaved leading prefix of the LIKE constant--and then build bounds from that
prefix. Your rules look good to me. That is, I haven't been able to come up with a problem
case. That's a bit shy of proof, of course. And I am a bit muddled by the interaction of the
Collator levers, strength and decomposition.

> Implement LIKE transformations and optimizations for databases using territory-based
collations
> -----------------------------------------------------------------------------------------------
>
>                 Key: DERBY-3854
>                 URL: https://issues.apache.org/jira/browse/DERBY-3854
>             Project: Derby
>          Issue Type: Improvement
>    Affects Versions: 10.3.3.0, 10.4.1.3, 10.5.0.0
>            Reporter: Rick Hillegas
>
> The LIKE transformations and optimizations are disabled when using a database with a
territory-based collation. See the following email thread: http://www.nabble.com/territory-based-collations-and-optimizations-for-the-LIKE-operator-td19111725.html#a19111725
That thread, in turn, refers to DERBY-1478. It would be nice if we did not have to perform
full table scans for LIKE queries in databases with territory-based collations.

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