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_r285871312
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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:
Moreover, I think `a in (select b from c)` is a `Correlated In` with a
`Non-Correlated Subquery`. And we are not going to use a subplan for it. We
only need to deal with the `Non-Correlated In`, whose left value should be
literal(or foldable) and the right subquery is non-correlated, such as `3 in
(select b from c)`.
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