Thejas M Nair commented on PIG-965:

In the above performance numbers, I assume optimization 2 (custom string 
comparison) is used only for the regex ".*ABCD.*" , while optimization 1 
(re-using compiled pattern) is used with dk.brics.automaton as well. Can you 
please confirm ?

>From the performance numbers, it looks like we don't need to do optimization 
>2. We can just use dk.brics.automaton for the common regexes as well and keep 
>the pig code simpler.

> 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
> 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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