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https://issues.apache.org/jira/browse/FLINK-41383?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18141288#comment-18141288
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Sergey Nuyanzin commented on FLINK-41383:
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Merged as
[fc2568fb9884e66538a51f83e5e861669b511969|https://github.com/apache/flink/commit/fc2568fb9884e66538a51f83e5e861669b511969]
> REGEXP, REGEXP_EXTRACT and REGEXP_REPLACE look up a constant pattern for
> every row
> -----------------------------------------------------------------------------------
>
> Key: FLINK-41383
> URL: https://issues.apache.org/jira/browse/FLINK-41383
> Project: Flink
> Issue Type: Technical Debt
> Components: Table SQL / Runtime
> Reporter: Sergey Nuyanzin
> Assignee: Sergey Nuyanzin
> Priority: Major
> Labels: pull-request-available
>
> These functions get their regex pattern from a cache. They do this for every
> row, even when the pattern is a constant in the query.
> The cache keeps only 64 patterns per thread. All regex functions share it. If
> a query uses more patterns, they push each other out. The patterns are then
> compiled again and again while the job runs.
> see
> -
> https://github.com/apache/flink/blob/master/flink-table/flink-table-common/src/main/java/org/apache/flink/table/utils/ThreadLocalCache.java#L35
> -
> https://github.com/apache/flink/blob/master/flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/functions/SqlFunctionUtils.java#L71
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