wangyum opened a new pull request #35287:
URL: https://github.com/apache/spark/pull/35287
### What changes were proposed in this pull request?
This pr add a new logical plan(`PartialDistinct`) to support partially
deduplicate input rows and use it push down limit through Aggregate if it is
group only.
For example:
```scala
spark.range(10000L).write.saveAsTable("t1")
spark.sql("SELECT DISTINCT * FROM t1 LIMIT 5").explain(true)
```
Before this pr:
```
== Optimized Logical Plan ==
GlobalLimit 5
+- LocalLimit 5
+- Aggregate [id#3L], [id#3L]
+- Relation default.t1[id#3L] parquet
```
After this pr:
```
== Optimized Logical Plan ==
GlobalLimit 5
+- LocalLimit 5
+- PartialDistinct
+- Relation default.t1[id#3L] parquet
```
### Why are the changes needed?
Improve query performance.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Unit test.
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