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From "Thejas M Nair (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-965) PERFORMANCE: optimize common case in matches (PORegex)
Date Thu, 17 Sep 2009 18:09:57 GMT
PERFORMANCE: optimize common case in matches (PORegex)
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                 Key: PIG-965
                 URL: https://issues.apache.org/jira/browse/PIG-965
             Project: Pig
          Issue Type: Improvement
          Components: impl
            Reporter: Thejas M Nair


Some frequently seen use cases of 'matches' comparison operator have follow properties -
1. The rhs is a constant string . eg "c1 matches 'abc%' "
2. Regexes such that look for matching prefix , suffix etc are very common. eg - "abc%', "%abc",
'%abc%' 

To optimize for these common cases , PORegex.java can be changed to -
1. Compile the pattern (rhs of matches) re-use it if the pattern string has not changed. 
2. Use string comparisons for simple common regexes (in 2 above).

The implementation of Hive like clause uses similar optimizations.



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