[jira] [Created] (FLINK-40141) Make IS_DECIMAL, IS_DIGIT, and IS_ALPHA return NULL for NULL input

["dylanhz (Jira)" <ji...@apache.org>]

dylanhz created FLINK-40141:
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             Summary: 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


{{}}

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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