Github user sameeragarwal commented on a diff in the pull request:
https://github.com/apache/spark/pull/15319#discussion_r84648114
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
---
@@ -74,20 +74,98 @@ 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 replacement will cause
an recursive deduction,
+ // when that happens a non-converging set of constraints will be
created and finally throw
+ // OOM Exception.
+ // For more details, refer to
https://issues.apache.org/jira/browse/SPARK-17733
+ val aliasMap = AttributeMap((expressions ++
children.flatMap(_.expressions)).collect {
+ case a: Alias => (a.toAttribute, a.child)
+ })
+
+ val equalExprSets = generateEqualExpressionSets(constraints, aliasMap)
+
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
+ val candidateConstraints = constraints - eq
+ inferredConstraints ++= candidateConstraints.map(_ transform {
+ case a: Attribute if a.semanticEquals(l) &&
+ !isRecursiveDeduction(r, aliasMap, equalExprSets) => r
})
- inferredConstraints ++= (constraints - eq).map(_ transform {
- case a: Attribute if a.semanticEquals(r) => l
+ inferredConstraints ++= candidateConstraints.map(_ transform {
+ case a: Attribute if a.semanticEquals(r) &&
+ !isRecursiveDeduction(l, aliasMap, equalExprSets) => l
})
case _ => // No inference
}
inferredConstraints -- constraints
}
+ /*
+ * Generate a sequence of expression sets from constraints, where each
set stores an equivalence
+ * class of expressions. For example, Set(`a = b`, `b = c`, `e = f`)
will generate the following
+ * expression sets: (Set(a, b, c), Set(e, f)). This will be used to
search all expressions equal
+ * to an selected attribute.
+ */
+ private def generateEqualExpressionSets(
+ constraints: Set[Expression],
+ aliasMap: AttributeMap[Expression]): Seq[Set[Expression]] = {
+ var equalExprSets = Seq.empty[Set[Expression]]
+ constraints.foreach {
+ case eq @ EqualTo(l: Attribute, r: Attribute) =>
+ // Transform [[Alias]] to its child.
+ val left = aliasMap.getOrElse(l, l)
+ val right = aliasMap.getOrElse(r, r)
+ // Get the expression set for equivalence class of expressions.
+ val leftEqualSet = getEqualExprSet(left,
equalExprSets).getOrElse(Set.empty[Expression])
+ val rightEqualSet = getEqualExprSet(right,
equalExprSets).getOrElse(Set.empty[Expression])
+ if (!leftEqualSet.isEmpty && !rightEqualSet.isEmpty) {
+ // Combine the two sets.
+ equalExprSets = equalExprSets.diff(leftEqualSet :: rightEqualSet
:: Nil) :+
+ (leftEqualSet ++ rightEqualSet)
+ } else if (!leftEqualSet.isEmpty) { // && rightEqualSet.isEmpty
+ // Update equivalence class of `left` expression.
+ equalExprSets = equalExprSets.diff(leftEqualSet :: Nil) :+
(leftEqualSet + right)
+ } else if (!rightEqualSet.isEmpty) { // && leftEqualSet.isEmpty
+ // Update equivalence class of `right` expression.
+ equalExprSets = equalExprSets.diff(rightEqualSet :: Nil) :+
(rightEqualSet + left)
+ } else { // leftEqualSet.isEmpty && rightEqualSet.isEmpty
+ // Create new equivalence class since both expression don't
present in any classes.
+ equalExprSets = equalExprSets :+ Set(left, right)
+ }
+ case _ => // Skip
+ }
+
+ equalExprSets
+ }
+
+ /*
+ * Get all expressions equivalent to the selected expression.
+ */
+ private def getEqualExprSet(
+ expr: Expression,
+ equalExprSets: Seq[Set[Expression]]): Option[Set[Expression]] =
+ equalExprSets.filter(_.contains(expr)).headOption
--- End diff --
can just have `equalExprSets.find(_.contains(expr))`
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