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[SPARK-19443][SQL] The function to generate constraints takes too long when the query plan grows continuously #16785

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[SPARK-19443][SQL] The function to generate constraints takes too long when the query plan grows continuously #16785

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b4e514a
Improve the code to generate constraints.
viirya Feb 3, 2017
8c98a5c
Use parallel collection to improve the function.
viirya Feb 9, 2017
1b9c561
Merge remote-tracking branch 'upstream/master' into improve-constrain…
viirya Feb 17, 2017
278c31c
Revert parallel collection approach. Reduce aliased constraints.
viirya Feb 17, 2017
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12 changes: 11 additions & 1 deletion sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -314,7 +314,17 @@ abstract class UnaryNode extends LogicalPlan {
* expressions with the corresponding alias
*/
protected def getAliasedConstraints(projectList: Seq[NamedExpression]): Set[Expression] = {
var allConstraints = child.constraints.asInstanceOf[Set[Expression]]
val relativeReferences = AttributeSet(projectList.collect {
case a: Alias => a
}.flatMap(_.references)) ++ outputSet

// We only care about the constraints which refer to attributes in output and aliases.
// For example, for a constraint 'a > b', if 'a' is aliased to 'c', we need to get aliased
// constraint 'c > b' only if 'b' is in output.
var allConstraints = child.constraints.filter { constraint =>
constraint.references.subsetOf(relativeReferences)
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@sameeragarwal sameeragarwal Feb 22, 2017

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Hi @viirya, I understand that #16998 probably supersedes this, but just out of curiosity, did you see a lot of benefit from pruning these attributes here given that we already prune them later in QueryPlan?

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@viirya viirya Feb 22, 2017

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Yes. You can see the benchmark in the pr description. With pruning these attributes, the running time is cut half.

If I understand your comment correctly, pruning them later in QueryPlan means we prune constraints which don't refer attributes in outputSet.

But the pruning here is happened before the pruning you pointed out, we need to reduce the constraints taken for transforming aliasing attributes to lower the computation cost.

}.asInstanceOf[Set[Expression]]

projectList.foreach {
case a @ Alias(e, _) =>
// For every alias in `projectList`, replace the reference in constraints by its attribute.
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