Ngone51 commented on a change in pull request #26629: [SPARK-29768][SQL] Column
pruning through nondeterministic expressions
URL: https://github.com/apache/spark/pull/26629#discussion_r350514186
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/patterns.scala
##########
@@ -74,24 +95,72 @@ object PhysicalOperation extends PredicateHelper {
case other =>
(None, Nil, other, AttributeMap(Seq()))
}
+}
- private def collectAliases(fields: Seq[Expression]):
AttributeMap[Expression] =
- AttributeMap(fields.collect {
- case a: Alias => (a.toAttribute, a.child)
- })
-
- private def substitute(aliases: AttributeMap[Expression])(expr: Expression):
Expression = {
- expr.transform {
- case a @ Alias(ref: AttributeReference, name) =>
- aliases.get(ref)
- .map(Alias(_, name)(a.exprId, a.qualifier))
- .getOrElse(a)
+/**
+ * A variant of [[PhysicalOperation]]. It matches any number of project or
filter
+ * operations even if they are non-deterministic, as long as they satisfy the
+ * requirement of CollapseProject and CombineFilters.
+ */
+object ScanOperation extends OperationHelper with PredicateHelper {
+ type ScanReturnType = Option[(Option[Seq[NamedExpression]],
+ Seq[Expression], LogicalPlan, AttributeMap[Expression])]
- case a: AttributeReference =>
- aliases.get(a)
- .map(Alias(_, a.name)(a.exprId, a.qualifier)).getOrElse(a)
+ def unapply(plan: LogicalPlan): Option[ReturnType] = {
+ collectProjectsAndFilters(plan) match {
+ case Some((fields, filters, child, _)) =>
+ Some((fields.getOrElse(child.output), filters, child))
+ case None => None
}
}
+
+ private def hasCommonNonDeterministic(expr: Seq[Expression], aliases:
AttributeMap[Expression])
+ : Boolean = {
+ expr.exists(_.collect {
+ case a: AttributeReference if aliases.contains(a) => aliases(a)
+ }.exists(!_.deterministic))
+ }
+
+ private def collectProjectsAndFilters(plan: LogicalPlan): ScanReturnType =
+ plan match {
+ case Project(fields, child) =>
+ collectProjectsAndFilters(child) match {
+ case Some((_, filters, other, aliases)) =>
+ // Follow CollapseProject and only keep going if the collected
Projects
+ // do not have common non-deterministic expressions.
Review comment:
Yeah, generally, I think so. But there's also suggestion of reducing
coupling between `Optimizer` and `Planner`. See:
https://github.com/apache/spark/pull/8486#issuecomment-136518354
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