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jibiyr edited comment on FLINK-21582 at 3/5/21, 1:58 PM: --------------------------------------------------------- [~twalthr] [~jark] hi wu,I found that coalsece is rewriter to case when after parse,when the case-when sqlNode after simplify is *cast('aa' as int) not null* ,so the case-when result is *cast('aa' as int) not null*,however the CAST ExprCodeGen resultTerm is null. I think the nullable of cast('aa' as int) should be true. was (Author: yr): [~twalthr] [~jark] hi wu,I found that coalsece is rewriter to case when after parse,when the case-when sqlNode after simplify ,the cast('aa' as int) is always true,so the case-when result is cast('aa' as int),however the value is null after reduceExpressionRule. should cast('aa' as int) should return a int value? or let it not always true. > COALESCE not works when cast a variable return null > --------------------------------------------------- > > Key: FLINK-21582 > URL: https://issues.apache.org/jira/browse/FLINK-21582 > Project: Flink > Issue Type: Bug > Components: Table SQL / API > Affects Versions: 1.11.1 > Environment: Flink1.11.1 > > Reporter: Jerry > Priority: Minor > Attachments: image-2021-03-03-19-48-21-306.png > > > select COALESCE(cast('aa' as int), 0);return NULL > select COALESCE(NULL, 0); return 0 > The first case works failed, but the second case works successful > -- This message was sent by Atlassian Jira (v8.3.4#803005)