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https://issues.apache.org/jira/browse/FLINK-34477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18104813#comment-18104813
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Gustavo de Morais commented on FLINK-34477:
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This also matters for performance, not just ergonomics. Without capture groups,
an "insert text here" rewrite has to be expressed as a zero-width lookaround
with a variable-length lookbehind, which Java brute-forces at every position.
On the approach: changing {{REGEXP_REPLACE}} in place is a breaking change. A
4th argument is a possibility but a bit ugly. Probably safer and cleaner to add
a new function than to change the existing one.
> support capture groups in REGEXP_REPLACE
> ----------------------------------------
>
> Key: FLINK-34477
> URL: https://issues.apache.org/jira/browse/FLINK-34477
> Project: Flink
> Issue Type: Improvement
> Components: Table SQL / API
> Affects Versions: 1.18.1
> Reporter: David Anderson
> Assignee: Jeyhun Karimov
> Priority: Major
> Labels: pull-request-available
>
> For example, I would expect this query
> {code:java}
> select REGEXP_REPLACE('ERR1,ERR2', '([^,]+)', 'AA$1AA'); {code}
> to produce
> {code:java}
> AAERR1AA,AAERR2AA{code}
> but instead it produces
> {code:java}
> AA$1AA,AA$1AA{code}
> With FLINK-9990 support was added for REGEXP_EXTRACT, which does provide
> access to the capture groups, but for many use cases supporting this in the
> way that users expect, in REGEXP_REPLACE, would be more natural and
> convenient.
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