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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (DERBY-2699) performance of like in territory based collation databases may be improved by changing way collation elements are calculated.
Date Mon, 05 Aug 2013 00:47:50 GMT

     [ https://issues.apache.org/jira/browse/DERBY-2699?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Mamta A. Satoor reassigned DERBY-2699:
--------------------------------------

    Assignee: Mamta A. Satoor  (was: Knut Anders Hatlen)
    
> performance of like in territory based collation databases may be improved by changing
way collation elements are calculated.
> -----------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-2699
>                 URL: https://issues.apache.org/jira/browse/DERBY-2699
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 10.3.1.4
>            Reporter: Mike Matrigali
>            Assignee: Mamta A. Satoor
>              Labels: derby_triage10_10
>             Fix For: 10.10.1.1
>
>         Attachments: d2699-1a.diff
>
>
> WorkHorseForCollatorDatatypes.java has a method getCollationElementsForString() which
currently gets
> called when processing like clauses in databases that have been created with territory
based collation, this is
> not an issue in pre-10.3 databases or post 10.3 default databases.
> getCollationElementsForString gets the collation elements for the entire  value of the
String held by
> the datatype using the class.
> If you take the case of pattern 'A%' and the value of datatype is 'BXXXXXXXXXXXXXXXXXXXXXXX',

> then it would have been better to  better to get collation elements one character of
the String value at a time
> to avoid the  process of getting collation elements for the entire string when we don't
really need it 
> One could imagine this might have a huge performance impact on running like against a
long clob where
> the like pattern has leading fixed-length pattern to match.
> Comments on this from Dan and Dag can be found in DERBY-2416.

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