## What changes were proposed in this pull request?
This pr fixed an issue when having multiple distinct aggregations having the same argument set, e.g.,
```
scala>: paste
val df = sql(
s"""SELECT corr(DISTINCT x, y), corr(DISTINCT y, x), count(*)
| FROM (VALUES (1, 1), (2, 2), (2, 2)) t(x, y)
""".stripMargin)
java.lang.RuntimeException
You hit a query analyzer bug. Please report your query to Spark user mailing list.
```
The root cause is that `RewriteDistinctAggregates` can't detect multiple distinct aggregations if they have the same argument set. This pr modified code so that `RewriteDistinctAggregates` could count the number of aggregate expressions with `isDistinct=true`.
## How was this patch tested?
Added tests in `DataFrameAggregateSuite`.
Author: Takeshi Yamamuro <yamamuro@apache.org>
Closes#21443 from maropu/SPARK-24369.
1e46f92f95