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https://issues.apache.org/jira/browse/FLINK-9559?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16594880#comment-16594880
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ASF GitHub Bot commented on FLINK-9559:
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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-416559091
Yes, sorry for my mistake there, I realised about it too late and was in the
process of fixing it, but it took me quite some time to find a way to determine
the actual data type returned from `case`.
In your examples, you are missing one important issue: what's the type of
string literal. Check out those examples:
PostgreSQL
http://sqlfiddle.com/#!17/c6522/1
- string literals are of `UNKNOWN` type, that behaves like `VARCHAR`
- `case when` on `CHAR` arguments returns `CHAR` type.
MSSQL:
http://sqlfiddle.com/#!18/50a92/1/0
(click `browser` schema button)
- string literals are `VARCHAR`
- `case when` return type strictly follows the standard - `CHAR(8)`
Oracle:
http://sqlfiddle.com/#!4/50a92/1/0
(click `browser` schema button)
- string literals are `CHAR`
- `case when` return type `VARCHAR`
This is still hardly conclusive to motivate the change for me.
I'm not sure why are you rejecting my proposal to change default string
literal type to `VARCHAR`. It would fix all of our `CHAR` problems
(comparisons, connector support, functions support, etc) for now and `case
when` would return `VARCHAR` automatically. Even if in the future we would want
to provide a configuration switch `string-literals-type: char/varchar`, such
configuration option would be cleaner and much easier to understand compared to
`shouldConvertRaggedUnionTypesToVarying`.
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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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