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https://issues.apache.org/jira/browse/CALCITE-2311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16476176#comment-16476176
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Julian Hyde commented on CALCITE-2311:
--------------------------------------
I agree this behavior is surprising, but it is not a bug. The return type of
the CASE expression is {{CHAR(3)}}. The result of evaluating {{CAST('a' AS
CHAR(3))}} is {{'a '}}.
> case when returns redundant white space
> ---------------------------------------
>
> Key: CALCITE-2311
> URL: https://issues.apache.org/jira/browse/CALCITE-2311
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.12.0
> Reporter: pengzhiwei
> Assignee: Julian Hyde
> Priority: Major
> Fix For: 1.17.0
>
>
> If the case-when expression has two branches which returns string
> literal,redundant white space will append to the short string literal after
> the ReduceExpressionsRule. For example:
> {code:java}
> case when id>0 then 'a' else 'abc' end{code}
> will actually be convert to
> {code:java}
> case when id>0 then 'a ' else 'abc' end{code}
>
> The reason is that the type of 'a' is CHAR(1),but CHAR(3) for 'abc',so the
> return type of the case-when is CHAR(3). The RexBuilder#ensureType() method
> append a cast convertion for 'a' to cast it to CHAR(3) type.The
> ReduceExpressionsRule execute the cast convertion which fill two whilte space
> to 'a'.
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