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https://issues.apache.org/jira/browse/PIG-965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12791096#action_12791096
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Ankit Modi commented on PIG-965:
--------------------------------
Here are numbers comparing comparing optimization 1&2 against optimization 1 &
dk.brics
dk.brics.Runautomaton is as fast as optimization 2 and also provides similar
speeds in a set of additional expressions.
|| Query || svn_trunk || std_dev || Optimization 1 & 2 || std_dev ||
Optimization 1 & brics.RunAutomaton || std_dev ||
| .\*ABCD.\* | 33.87 | 0.71 | 18.77 | 0.71 | 18.94 | 0.02 |
| .\*ABCD | 30.06 | 2.91 | 18.44 | 0.05 | 18.94 | 0.03 |
| ABCD.\* | 21.93 | 2.91 | 18.35 | 0.1 | 18.85 | 0.04 |
Values are averaged over 3 runs.
> PERFORMANCE: optimize common case in matches (PORegex)
> ------------------------------------------------------
>
> Key: PIG-965
> URL: https://issues.apache.org/jira/browse/PIG-965
> Project: Pig
> Issue Type: Improvement
> Components: impl
> Reporter: Thejas M Nair
> Assignee: Ankit Modi
> Attachments: automaton.jar, poregex2.patch
>
>
> 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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