[jira] [Created] (FLINK-9559) The type of a union of CHAR columns of different lengths should be VARCHAR

["Hequn Cheng (JIRA)" <ji...@apache.org>]

Hequn Cheng created FLINK-9559:
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             Summary: The type of a union of CHAR columns of different lengths should be VARCHAR
                 Key: FLINK-9559
                 URL: https://issues.apache.org/jira/browse/FLINK-9559
             Project: Flink
          Issue Type: Improvement
          Components: Table API & SQL
            Reporter: Hequn Cheng
            Assignee: Hequn Cheng


Currently, If the case-when expression has two branches which return string literal, redundant white spaces will be appended to the short string literal. For example, for the sql: case 1 when 1 then 'a' when 2 then 'bcd' end, the return value will be 'a ' of CHAR(3) instead of 'a'.

Although, this follows the behavior in strict SQL standard mode(SQL:2003). We should get the pragmatic return type in a real scenario without blank-padded. 

Happily, this problem has been fixed by [CALCITE-2321|https://issues.apache.org/jira/browse/CALCITE-2321], we can upgrade calcite to the next release(1.17.0) and override {{RelDataTypeSystem}} in flink to configure the return type, i.e., making {{shouldConvertRaggedUnionTypesToVarying()}} return true.





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