[ https://issues.apache.org/jira/browse/DERBY-2699?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13729138#comment-13729138
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ASF subversion and git services commented on DERBY-2699:
--------------------------------------------------------
Commit 1510373 from [~mamtas] in branch 'code/branches/10.8'
[ https://svn.apache.org/r1510373 ]
DERBY-2699(performance of like in territory based collation databases may be improved by changing
way collation elements are calculated.)
Backporting to 10.8. Fix contributed by 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: 10.9.2.2, 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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