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https://issues.apache.org/jira/browse/DRILL-4573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15301047#comment-15301047
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Jinfeng Ni commented on DRILL-4573:
-----------------------------------
It's true that CharBuffer can be re-used and grown if needed, since it can be
pre-allocated per fragment operator. However, decoder.decode(byteBuf,
charBuffer, endOfInput) is actually doing copy row. I'm curious how much
performance improvement we are looking at.
> 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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