maropu commented on a change in pull request #32586:
URL: https://github.com/apache/spark/pull/32586#discussion_r634978302
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
##########
@@ -167,7 +167,23 @@ class EquivalentExpressions {
* Returns all the equivalent sets of expressions.
*/
def getAllEquivalentExprs: Seq[Seq[Expression]] = {
- equivalenceMap.values.map(_.toSeq).toSeq
+ equivalenceMap.values.map(_.toSeq).toSeq.sortBy(_.head)(new
ExpressionOrdering)
+ }
+
+ /**
+ * Orders [Expression] by parent/child relations. The child expression is
smaller
+ * than parent expression.
Review comment:
> If there is child-parent relationships among the subexpressions, we
want the child expressions come first than parent expressions, so we can
replace child expressions in parent expressions with subexpression evaluation.
How about leaving this comment here? I think this explanation looks clearer.
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