c21 commented on a change in pull request #31595:
URL: https://github.com/apache/spark/pull/31595#discussion_r581222939
##########
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:
@viirya - in
https://github.com/apache/spark/compare/80b03dd64e317...c21:remove-union, I am
testing this query:
```
select distinct key, expr
from
(
select key, key + 1 as expr
from testData
union all
select key, key + 2 as expr
from testData
)
```
Optimized logical plan with the rule:
```
== Optimized Logical Plan ==
Aggregate [key#14, expr#18], [key#14, expr#18]
+- Project [key#14, (key#14 + 1) AS expr#18]
+- SerializeFromObject [knownnotnull(assertnotnull(input[0,
org.apache.spark.sql.test.SQLTestData$TestData4, true])).key AS key#14]
+- ExternalRDD [obj#13]
```
Optimized logical plan without the rule:
```
== Optimized Logical Plan ==
Aggregate [key#2, expr#6], [key#2, expr#6]
+- Union false, false
:- Project [key#2, (key#2 + 1) AS expr#6]
: +- SerializeFromObject [knownnotnull(assertnotnull(input[0,
org.apache.spark.sql.test.SQLTestData$TestData4, true])).key AS key#2]
: +- ExternalRDD [obj#1]
+- Project [key#2, (key#2 + 2) AS expr#9]
+- SerializeFromObject [knownnotnull(assertnotnull(input[0,
org.apache.spark.sql.test.SQLTestData$TestData4, true])).key AS key#2]
+- ExternalRDD [obj#1]
```
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