Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/16954#discussion_r102168672
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
---
@@ -1110,31 +1184,24 @@ class Analyzer(
}
/**
- * Pull out all (outer) correlated predicates from a given subquery.
This method removes the
- * correlated predicates from subquery [[Filter]]s and adds the
references of these predicates
- * to all intermediate [[Project]] and [[Aggregate]] clauses (if they
are missing) in order to
- * be able to evaluate the predicates at the top level.
- *
- * This method returns the rewritten subquery and correlated
predicates.
+ * Validates to make sure the outer references appearing inside the
subquery
+ * are legal. This function also returns the list of expressions
+ * that contain outer references. These outer references would be kept
as children
+ * of subquery expressions by the caller of this function.
*/
- private def pullOutCorrelatedPredicates(sub: LogicalPlan):
(LogicalPlan, Seq[Expression]) = {
- val predicateMap = scala.collection.mutable.Map.empty[LogicalPlan,
Seq[Expression]]
+ private def checkAndGetOuterReferences(sub: LogicalPlan):
Seq[Expression] = {
+ val outerReferences =
scala.collection.mutable.ArrayBuffer.empty[Seq[Expression]]
--- End diff --
Nit: `ArrayBuffer.empty[Seq[Expression]]` should also work. Why is it
useful to collect sequences of expressions instead of just expressions?
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