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https://issues.apache.org/jira/browse/FLINK-9559?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16571814#comment-16571814
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ASF GitHub Bot commented on FLINK-9559:
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hequn8128 opened a new pull request #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
## What is the purpose of the change
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'.
This pr tries to solve the redundant white spaces problem.
## Brief change log
- Override `shouldConvertRaggedUnionTypesToVarying` to true in
`FlinkTypeSystem`, so that Calcite will return CHAR to VARCHAR when infer
result type for CHAR with different length.
- Adapt some old tests.
- Add more tests.
## Verifying this change
This change is already covered by existing tests, such as `testValues` in
`JavaSqlITCase` and `testOtherExpressions` in `ScalarOperatorsTest`.
Also add more tests in `ScalarOperatorsTest`.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (no)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (no)
- The serializers: (no)
- The runtime per-record code paths (performance sensitive): (no)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Yarn/Mesos, ZooKeeper: (no)
- The S3 file system connector: (no)
## Documentation
- Does this pull request introduce a new feature? (no)
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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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