[jira] [Commented] (DRILL-4573) Zero copy LIKE, REGEXP_MATCHES, SUBSTR

["Jacques Nadeau (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-4573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15266030#comment-15266030 ] 

Jacques Nadeau commented on DRILL-4573:
---------------------------------------

You should avoid mutating the input buffer. It should be treated as immutable as it could be shared between multiple threads.

> Zero copy LIKE, REGEXP_MATCHES, SUBSTR
> --------------------------------------
>
>                 Key: DRILL-4573
>                 URL: https://issues.apache.org/jira/browse/DRILL-4573
>             Project: Apache Drill
>          Issue Type: Improvement
>            Reporter: jean-claude
>            Priority: Minor
>             Fix For: 1.7.0
>
>         Attachments: DRILL-4573-3.patch.txt, DRILL-4573.patch.txt
>
>
> All the functions using the java.util.regex.Matcher are currently creating Java string objects to pass into the matcher.reset().
> However this creates unnecessary copy of the bytes and a Java string object.
> The matcher uses a CharSequence, so instead of making a copy we can create an adapter from the DrillBuffer to the CharSequence interface.
> Gains of 25% in execution speed are possible when going over VARCHAR of 36 chars. The gain will be proportional to the size of the VARCHAR.



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