Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/10630#discussion_r49094926
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -966,6 +952,22 @@ object ReplaceDistinctWithAggregate extends
Rule[LogicalPlan] {
}
/**
+ * Replaces logical [[Intersect]] operator with a left-semi [[Join]]
operator.
+ * {{{
+ * SELECT a1, a2 FROM Tab1 INTERSECT SELECT b1, b2 FROM Tab2
+ * ==> SELECT a1, a2 FROM Tab1 LEFT SEMI JOIN Tab2 ON a1<=>b1 AND
a2<=>b2
+ * }}}
+ */
+object ReplaceIntersectWithSemiJoin extends Rule[LogicalPlan] {
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ case Intersect(left, right) =>
+ assert(left.output.size == right.output.size)
+ val joinCond = left.output.zip(right.output).map { case (l, r) =>
EqualNullSafe(l, r) }
+ Join(left, right, LeftSemi, joinCond.reduceLeftOption(And))
--- End diff --
You are right! It should remove duplicates. I just tried it in DB2.
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