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https://issues.apache.org/jira/browse/DRILL-4573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15301532#comment-15301532
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Jinfeng Ni commented on DRILL-4573:
-----------------------------------
One thing you may consider: use different logic for ASCII string and non-ASCII
string. You can easily scan the input byte array and detect it falls into which
category. For the 1st case, you can use your zero-copy logic. For 2nd case, it
has to do copy. This way, we get much better performance for more commonly used
ASCII string, and not-worse-than-before performance for non-ASCII string.
> 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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