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From "Jacques Nadeau (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4573) Zero copy LIKE, REGEXP_MATCHES, SUBSTR
Date Mon, 02 May 2016 15:47:12 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15266840#comment-15266840
] 

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

When we started working on functions, immutability wasn't a constraint so we may have a few
functions around that don't follow this rule. The goal is go back and correct those but make
sure we don't add any new mutations.

> 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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