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https://issues.apache.org/jira/browse/FLINK-40141?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18103326#comment-18103326
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Bettle commented on FLINK-40141:
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Hi, I’d like to work on this issue as my first contribution to Apache Flink. I
reviewed the current implementation and plan to fix the null propagation and
nullable return type inference for {{{}IS_DECIMAL{}}}, {{{}IS_DIGIT{}}}, and
{{{}IS_ALPHA{}}}, and update the corresponding tests and documentation. Could a
committer please confirm the approach and assign the issue to me? Thanks!
> Make IS_DECIMAL, IS_DIGIT, and IS_ALPHA return NULL for NULL input
> ------------------------------------------------------------------
>
> Key: FLINK-40141
> URL: https://issues.apache.org/jira/browse/FLINK-40141
> Project: Flink
> Issue Type: Technical Debt
> Components: Table SQL / Planner
> Reporter: dylanhz
> Priority: Minor
>
> {{}}
> The Flink-specific predicates {{{}IS_DECIMAL{}}}, {{{}IS_DIGIT{}}}, and
> {{IS_ALPHA}} currently return {{FALSE}} for SQL {{NULL}} input and produce a
> non-nullable {{{}BOOLEAN{}}}.
> For consistency with SQL null propagation, they should:
> * Return {{NULL}} for {{NULL}} input.
> * Produce a nullable result when the input is nullable.
> * Keep the existing behavior for non-null inputs.
> This is related to the discussion around FLINK-39943 and should be treated as
> a documented behavior change.
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