beyond1920 opened a new pull request #14602:
URL: https://github.com/apache/flink/pull/14602
## What is the purpose of the change
An `Expand` node is only necessary when multiple aggregate function with
different distinct keys appear in an Aggregate. However an unnecessary `Expand`
node will be generated under some special cases, like the following sql.
SELECT COUNT(c) AS pv, COUNT(DISTINCT c) AS uv FROM T GROUP BY a.
This pull request aims to avoid generate unnecessary `Expand` node.
## Brief change log
- `SplitAggregateRule` check only need expand if there are multiple
distinct aggregate functions in an Aggregate
## Verifying this change
This change is already covered by existing tests, such as
`SplitAggregateITCase`, `DistinctAggregateTest`, `SplitAggregateRuleTest` .
Besides, this change added IT and UT in `SplitAggregateITCase` and
`SplitAggregateRuleTest`
## 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, Kubernetes/Yarn/Mesos, ZooKeeper: (no)
- The S3 file system connector: (no)
## Documentation
- Does this pull request introduce a new feature? (no)
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