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From "Mike Matrigali (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-2698) caching collation elements in WorkHorseForCollatorDatatypes may improve performance.
Date Sat, 26 May 2007 00:10:16 GMT
caching collation elements in WorkHorseForCollatorDatatypes may improve performance.
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                 Key: DERBY-2698
                 URL: https://issues.apache.org/jira/browse/DERBY-2698
             Project: Derby
          Issue Type: Improvement
          Components: SQL
    Affects Versions: 10.3.0.0
            Reporter: Mike Matrigali
            Priority: Minor


In java/engine/org/apache/derby/iapi/types/WorkHorseForCollatorDatatypes.getCollationElementsForString()
an array
of int's is calculated given the string and the collator in place.  If like is ever called
on the same DataValueDescriptor, caching
this calculation will be faster than redoing the calculation.  To make this change one needs
to properly invalidate the cached
information when the base type value is changed.  For instance in the case of SQLChar() the
following routines all result
in a change in the value of the datatype and thus need to invalidate any cached collation
element structure:
readExternalFromArray()
readExternal()
setValue()
there may be others.

DERBY-2670 is an example of what can go wrong if you get the caching wrong.




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