zzcclp commented on a change in pull request #31404:
URL: https://github.com/apache/spark/pull/31404#discussion_r575769956
##########
File path:
sql/core/src/test/scala/org/apache/spark/sql/DataFrameSetOperationsSuite.scala
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@@ -385,6 +385,90 @@ class DataFrameSetOperationsSuite extends QueryTest with
SharedSparkSession {
checkAnswer(unionDF, unionAllDF)
}
+ test("SQL-style union using Dataset: remove unnecessary deduplicate in
multiple unions") {
+ val unionDF =
testData.union(testData).distinct().union(testData).distinct()
+ .union(testData).distinct().union(testData).distinct()
+
+ // Before optimizer, there are three 'union.deduplicate' operations should
be combined.
+ assert(unionDF.queryExecution.analyzed.collect {
+ case j: Union if j.children.size == 4 => j
Review comment:
IMO, it's more intuitional to count the number of Union, and the test
cases related to Union above use this way to check.
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