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https://issues.apache.org/jira/browse/FLINK-5315?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16572373#comment-16572373
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ASF GitHub Bot commented on FLINK-5315:
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walterddr opened a new pull request #6521: [FLINK-5315][table] Adding support
for distinct operation for table API on DataStream
URL: https://github.com/apache/flink/pull/6521
## What is the purpose of the change
* Adding `distinct` aggregation support for Table API. Example usages are:
- For built-in expressions `'a.count.distinct`
- For user-defined aggregate functions `udaggFunc.distinct('a, 'b)`
## Brief change log
- *Added `distinctAgg` operator in expression as aggregation*
- *Create aggregation resolve rules in `operators` to accept distinct
aggregation modifier before getting to actual aggregation*
- *Modified UDAGG function interface to add `distinct` modifier API*
## Verifying this change
This change added tests and can be verified as follows:
- *Added integration tests for UDAGG Function call and Expression
aggregation, respectively. *
- *Added unit-test for both cases (prefix modifier for UDAGG, and suffix
modifier for expressions) as well as added unsupported use cases (suffix
modifier for UDAGG).
- *Backward compatibility for other aggregations are covered with existing
unit-test*
## 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, but added `private[flink]` modifier for
`AggregationFunction` API which might have been exposed to Java API)
- 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? (yes)
- If yes, how is the feature documented? (not documented yet)
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> Support distinct aggregations in table api
> ------------------------------------------
>
> Key: FLINK-5315
> URL: https://issues.apache.org/jira/browse/FLINK-5315
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: Kurt Young
> Assignee: Rong Rong
> Priority: Major
> Labels: pull-request-available
>
> Support distinct aggregations in Table API in the following format:
> For Expressions:
> {code:scala}
> 'a.count.distinct // Expressions distinct modifier
> {code}
> For User-defined Function:
> {code:scala}
> singleArgUdaggFunc.distinct('a) // FunctionCall distinct modifier
> multiArgUdaggFunc.distinct('a, 'b) // FunctionCall distinct modifier
> {code}
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