Github user sameeragarwal commented on a diff in the pull request:
https://github.com/apache/spark/pull/15319#discussion_r83791645
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
---
@@ -74,14 +74,26 @@ abstract class QueryPlan[PlanType <:
QueryPlan[PlanType]] extends TreeNode[PlanT
* additional constraint of the form `b = 5`
*/
private def inferAdditionalConstraints(constraints: Set[Expression]):
Set[Expression] = {
+ // Collect alias from expressions to avoid producing non-converging
set of constraints
+ // for recursive functions.
+ //
+ // Don't apply transform on constraints if the attribute used to
replace is an alias,
+ // because then both `QueryPlan.inferAdditionalConstraints` and
+ // `UnaryNode.getAliasedConstraints` applies and may produce a
non-converging set of
+ // constraints.
+ // For more details, refer to
https://issues.apache.org/jira/browse/SPARK-17733
+ val aliasSet = AttributeSet((expressions ++
children.flatMap(_.expressions)).collect {
+ case a: Alias => a.toAttribute
+ })
+
var inferredConstraints = Set.empty[Expression]
constraints.foreach {
case eq @ EqualTo(l: Attribute, r: Attribute) =>
inferredConstraints ++= (constraints - eq).map(_ transform {
- case a: Attribute if a.semanticEquals(l) => r
+ case a: Attribute if a.semanticEquals(l) &&
!aliasSet.contains(r) => r
--- End diff --
@jiangxb1987 isn't this a fairly restrictive way to solve this problem? You
are essentially not inferring any additional constraints from those that
contain aliases. For e.g., if we have have a query `SELECT a AS a1, b AS b1
WHERE a1 = 1 AND a1 = b1`, this change would never allow us to infer a
filter/constraint on `b = 1`. Can we identify and just disallow recursive
constraints?
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