beliefer commented on code in PR #44009:
URL: https://github.com/apache/spark/pull/44009#discussion_r1404844214
##########
sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/LimitPushdownSuite.scala:
##########
@@ -352,4 +352,21 @@ class LimitPushdownSuite extends PlanTest {
comparePlans(Optimize.execute(originalQuery2), originalQuery2)
}
}
+
+ test("SPARK-46097: Push down limit 1 though Union and Aggregate") {
+ val unionQuery = Union(
+ Union(
+ testRelation.groupBy($"a", $"b")($"a", $"b"),
+ testRelation2.groupBy($"d", $"e")($"d", $"e"),
+ ),
+ testRelation2.groupBy($"e", $"f")($"e", $"f")).limit(1)
+
+ val correctAnswer = Union(
+ Union(
+ LocalLimit(1, testRelation).select($"a", $"b"),
+ LocalLimit(1, testRelation2).select($"d", $"e")).limit(1),
+ LocalLimit(1, testRelation2).select($"e", $"f")).limit(1)
+
+ comparePlans(Optimize.execute(unionQuery.analyze), correctAnswer.analyze)
Review Comment:
This test case only ensure the logical plan. Could you add a test case to
compare the output data?
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala:
##########
@@ -771,6 +771,17 @@ object LimitPushDown extends Rule[LogicalPlan] {
Limit(le, Project(a.aggregateExpressions, LocalLimit(le, a.child)))
case Limit(le @ IntegerLiteral(1), p @ Project(_, a: Aggregate)) if
a.groupOnly =>
Limit(le, p.copy(child = Project(a.aggregateExpressions, LocalLimit(le,
a.child))))
+ // Push down limit 1 though Union and Aggregate
+ case Limit(le @ IntegerLiteral(1), u: Union) =>
+ val newUnionChildren = u.children.map {
+ case a: Aggregate if a.groupOnly =>
Review Comment:
I doubt that the output will be changed.
`limit 1 after shuffle` is not the same as `limit 1 before shuffle`
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