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https://issues.apache.org/jira/browse/FLINK-9559?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16591783#comment-16591783
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ASF GitHub Bot commented on FLINK-9559:
---------------------------------------
pnowojski commented on issue #6519: [FLINK-9559] [table] The type of a union of
CHAR columns of different lengths should be VARCHAR
URL: https://github.com/apache/flink/pull/6519#issuecomment-415789873
@hequn8128 I'm pretty sure that what you have just pointed out is bug in
Flink SQL. I'm not 100% sure (maybe 95%), but when comparing different types
like `CHAR(3)` with `CHAR(5)` or `VARCHAR(2)`, all of the operands should be
first converted to same type (adding/ignoring padding when necessary) and only
then compared.
In other words `'A ' == 'A'` should return true, and this PR is not a
proper fix to this problem. It doesn't fix for example:
```
SELECT * FROM country WHERE country_name = 'GERMANY '
```
This further convinces me that:
> and our CHAR(x) support seems to be broken (for example 'A ' || 'B '
should return 'A B ')
Probably either we should convert string literals to `VARCHAR` or properly
implement support for `CHAR`
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> 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: Bug
> Components: Table API & SQL
> Reporter: Hequn Cheng
> Assignee: Hequn Cheng
> Priority: Major
> Labels: pull-request-available
>
> 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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