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https://issues.apache.org/jira/browse/FLINK-9559?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16595540#comment-16595540
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ASF GitHub Bot commented on FLINK-9559:
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pnowojski edited a comment 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-416647706
Good point with the comparisons. I meant that after changing literal types
to `VARCHAR` (and accepting that this brakes SQL standard) our
comparisons/functions (like `concat`) would be more SQL standard compliant,
without the need to fix them. Saying that our literals are `VARCHAR` and we are
being consistent with handling them is better then providing broken `CHAR`.
Also it should be a cheaper and way easier for us compared to finding all
places that do not handle `CHAR` as they should and fixing them. As a side
note, I generally consider `CHAR` as a pretty useless type, especially since
unicode it's no longer fixed length.
Changing type of string literal would be easy in calcite
(`org.apache.calcite.rex.RexBuilder#makePreciseStringLiteral`).
On our side it's might a little bit be more tricky. I might be wrong here,
but it might be enough to provide `RexShuttle` that do `CHAR` to `VARCHAR` type
rewrite and apply it to
`org.apache.calcite.rel.AbstractRelNode#accept(org.apache.calcite.rex.RexShuttle)`
as a yet another "zero" step. Which also doesn't sound overly complicated.
`shouldConvertRaggedUnionTypesToVarying` both with better `CHAR` support or
`VARCHAR` literals looses it's purpose (and becomes cosmetic change), or
doesn't it?
Since I consider this our `CHAR` handling to be a serious problem, I would
like it to be fixed (in one way or the other) before 1.7.0 release. If we could
fix this properly, would you be fine with proper fix superseding this PR? If we
would be running out of time, we could reevaluate this closer to feature freeze.
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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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