viirya commented on a change in pull request #32586:
URL: https://github.com/apache/spark/pull/32586#discussion_r636514764
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/EquivalentExpressions.scala
##########
@@ -167,7 +167,28 @@ 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
ExpressionContainmentOrdering)
+ }
+
+ /**
+ * Orders [Expression] by parent/child relations. The child expression is
smaller
+ * than parent expression. 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.
Note that
+ * this is not for general expression ordering. For example, two irrelevant
expressions
+ * will be considered as e1 < e2 and e2 < e1 by this ordering. But for the
usage here,
+ * the order of irrelevant expressions does not matter.
+ */
+ class ExpressionContainmentOrdering extends Ordering[Expression] {
+ override def compare(x: Expression, y: Expression): Int = {
+ if (x.semanticEquals(y)) {
+ 0
+ } else if (x.find(_.semanticEquals(y)).isDefined) {
Review comment:
BTW, I think better approach is to sort after filter (e.g. size > 1 in
most use-case), because the number of sub-exprs should be smaller.
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