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https://issues.apache.org/jira/browse/DRILL-4573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15265318#comment-15265318
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jean-claude commented on DRILL-4573:
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I attached patch DRILL-4573-3
It fixes the issue reported DRILL-4645
The CharSequenceWrapper.toString() method was called.
I decided to in-line the Matcher.replaceAll() to avoid creating that String
altogether.
Notice in the case there is nothing to replace I copy the input buffer into the
output buffer. Can you confirm that is the best way to copy the input buffer
into the output buffer?
> 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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