francis0407 commented on a change in pull request #24344: [SPARK-27440][SQL]
Optimize uncorrelated predicate subquery
URL: https://github.com/apache/spark/pull/24344#discussion_r285874715
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/subquery.scala
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@@ -93,6 +93,21 @@ object SubqueryExpression {
}.isDefined
}
+ /**
+ * Returns true when an expression contains a correlated IN or correlated
EXISTS and
+ * false otherwise. An IN is non-correlated only if the left values are
foldable
+ * and the subquery has no outer references.
+ */
+ def hasCorrelatedInOrExists(e: Expression): Boolean = {
Review comment:
@dilipbiswal Yes, currently we get all the result of the subquery to the
driver. But we can use some methods (not in this PR) to reduce the result set
in the executor side.
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