[GitHub] [spark] cloud-fan commented on a change in pull request #24344: [SPARK-27440][SQL] Optimize uncorrelated predicate subquery

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cloud-fan commented on a change in pull request #24344: [SPARK-27440][SQL] Optimize uncorrelated predicate subquery
URL: https://github.com/apache/spark/pull/24344#discussion_r285867101
 
 

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 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:
   a general question: what's the difference between this and `hasCorrelatedSubquery`? It seems to me that `In` or `Exists` are subqueries, so `hasCorrelatedSubquery` should cover it.

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