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https://issues.apache.org/jira/browse/DRILL-4573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15229499#comment-15229499
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jean-claude commented on DRILL-4573:
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You can test the performance gain by creating a simple csv file with one column
containing UUID like this
for i in {1..1000000}; do uuidgen; done > /Users/jccote/test.csv
then query using drill
select count(1) from dfs.`/Users/jccote/test.csv` where columns[0] like '0%';
run it multiple times to get a good estimate
> 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
> Attachments: DRILL-4573.1.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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