viirya commented on a change in pull request #31595:
URL: https://github.com/apache/spark/pull/31595#discussion_r580913391
##########
File path:
sql/core/src/test/scala/org/apache/spark/sql/DataFrameSetOperationsSuite.scala
##########
@@ -808,6 +813,53 @@ class DataFrameSetOperationsSuite extends QueryTest with
SharedSparkSession {
// scalastyle:on
checkAnswer(union, row1 :: row2 :: Nil)
}
+
+ test("SPARK-34474: Remove unnecessary Union under Distinct") {
+ Seq(RemoveNoopUnion.ruleName, "").map { ruleName =>
+ withSQLConf(SQLConf.OPTIMIZER_EXCLUDED_RULES.key -> ruleName) {
+ val distinctUnionDF1 = testData.union(testData).distinct()
+ checkAnswer(distinctUnionDF1, testData.distinct())
+
+
+ val distinctUnionDF2 =
testData.union(testData).dropDuplicates(Seq("key"))
+ checkAnswer(distinctUnionDF2, testData.dropDuplicates(Seq("key")))
+
+ val distinctUnionDF3 = sql(
+ """
+ |select key, value from testData
+ |union
+ |select key, value from testData
+ |""".stripMargin)
+ checkAnswer(distinctUnionDF3, testData.distinct())
+
+ val distinctUnionDF4 = sql(
+ """
+ |select distinct key, expr
+ |from
+ |(
+ | select key, key + 1 as expr
+ | from testData
+ | union all
+ | select key, key + 2 as expr
+ | from testData
+ |)
Review comment:
I posted the query plan with/without this rule for the query from the
diff in the above link. I don't see the query plan is different. I'm not sure
which query plan is wrong?
```
sql(
"""
|select key, key + 2 as expr
|from testData4
|""".stripMargin)
```
```
== Physical Plan ==
*(1) Project [key#2641, (key#2641 + 2) AS expr#2645]
+- *(1) SerializeFromObject [knownnotnull(assertnotnull(input[0,
org.apache.spark.sql.test.SQLTestData$TestData4, true])).key AS key#2641]
+- Scan[obj#2640]
```
```
== Physical Plan ==
*(1) Project [key#2732, (key#2732 + 2) AS expr#2736]
+- *(1) SerializeFromObject [knownnotnull(assertnotnull(input[0,
org.apache.spark.sql.test.SQLTestData$TestData4, true])).key AS key#2732]
+- Scan[obj#2731]
```
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