maropu commented on a change in pull request #23750: [SPARK-19712][SQL] Pushing
Left Semi and Left Anti joins through Project, Aggregate, Window, Union etc.
URL: https://github.com/apache/spark/pull/23750#discussion_r256815912
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
##########
@@ -1188,6 +1189,190 @@ object PushDownPredicate extends Rule[LogicalPlan]
with PredicateHelper {
}
}
+object PushDownLeftSemiAntiJoin extends Rule[LogicalPlan] with PredicateHelper
{
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ // Similar to the above Filter over Project
+ // LeftSemi/LeftAnti over Project
+ case join @ Join(p @ Project(pList, gChild), rightOp,
LeftSemiOrAnti(joinType), joinCond, hint)
+ if pList.forall(_.deterministic) &&
!ScalarSubquery.hasScalarSubquery(pList) &&
+ canPushThroughCondition(Seq(gChild), joinCond, rightOp) =>
+ if (joinCond.isEmpty) {
+ // No join condition, just push down the Join below Project
+ Project(pList, Join(gChild, rightOp, joinType, joinCond, hint))
+ } else {
+ // Create a map of Aliases to their values from the child projection.
+ // e.g., 'SELECT a + b AS c, d ...' produces Map(c -> a + b).
+ val aliasMap = AttributeMap(pList.collect {
+ case a: Alias => (a.toAttribute, a.child)
+ })
+ val newJoinCond = if (aliasMap.nonEmpty) {
+ Option(replaceAlias(joinCond.get, aliasMap))
+ } else {
+ joinCond
+ }
+ Project(pList, Join(gChild, rightOp, joinType, newJoinCond, hint))
+ }
+
+ // Similar to the above Filter over Aggregate
+ // LeftSemi/LeftAnti over Aggregate
+ case join @ Join(aggregate: Aggregate, rightOp, LeftSemiOrAnti(joinType),
joinCond, hint)
+ if aggregate.aggregateExpressions.forall(_.deterministic)
+ && aggregate.groupingExpressions.nonEmpty =>
+ if (joinCond.isEmpty) {
+ // No join condition, just push down Join below Aggregate
+ aggregate.copy(child = Join(aggregate.child, rightOp, joinType,
joinCond, hint))
+ } else {
+ // Find all the aliased expressions in the aggregate list that don't
include any actual
+ // AggregateExpression, and create a map from the alias to the
expression
+ val aliasMap = AttributeMap(aggregate.aggregateExpressions.collect {
+ case a: Alias if
a.child.find(_.isInstanceOf[AggregateExpression]).isEmpty =>
+ (a.toAttribute, a.child)
+ })
+
+ // For each join condition, expand the alias and
+ // check if the condition can be evaluated using
+ // attributes produced by the aggregate operator's child operator.
+
+ val (pushDown, stayUp) =
splitConjunctivePredicates(joinCond.get).partition { cond =>
+ val replaced = replaceAlias(cond, aliasMap)
+ cond.references.nonEmpty &&
+ replaced.references.subsetOf(aggregate.child.outputSet ++
rightOp.outputSet)
+ }
+
+ // Check if the remaining predicates do not contain columns from
subquery
+ val rightOpColumns =
AttributeSet(stayUp.toSet).intersect(rightOp.outputSet)
+
+ if (pushDown.nonEmpty && rightOpColumns.isEmpty) {
+ val pushDownPredicate = pushDown.reduce(And)
+ val replaced = replaceAlias(pushDownPredicate, aliasMap)
+ val newAggregate = aggregate.copy(child =
+ Join(aggregate.child, rightOp, joinType, Option(replaced), hint))
+ // If there is no more filter to stay up, just return the Aggregate
over Join.
+ // Otherwise, create "Filter(stayUp) <- Aggregate <-
Join(pushDownPredicate)".
+ if (stayUp.isEmpty) newAggregate else Filter(stayUp.reduce(And),
newAggregate)
+ } else {
+ // The join condition is not a subset of the Aggregate's GROUP BY
columns,
+ // no push down.
+ join
+ }
+ }
+
+ // Similar to the above Filter over Window
+ // LeftSemi/LeftAnti over Window
+ case join @ Join(w: Window, rightOp, LeftSemiOrAnti(joinType), joinCond,
hint)
+ if w.partitionSpec.forall(_.isInstanceOf[AttributeReference]) =>
+ if (joinCond.isEmpty) {
+ // No join condition, just push down Join below Window
+ w.copy(child = Join(w.child, rightOp, joinType, joinCond, hint))
+ } else {
+ val partitionAttrs =
AttributeSet(w.partitionSpec.flatMap(_.references)) ++
+ rightOp.outputSet
+
+ val (pushDown, stayUp) =
splitConjunctivePredicates(joinCond.get).partition { cond =>
+ cond.references.subsetOf(partitionAttrs)
+ }
+
+ // Check if the remaining predicates do not contain columns from
subquery
+ val rightOpColumns =
AttributeSet(stayUp.toSet).intersect(rightOp.outputSet)
+
+ if (pushDown.nonEmpty && rightOpColumns.isEmpty) {
+ val pushDownPredicate = pushDown.reduce(And)
+ val newPlan =
+ w.copy(child = Join(w.child, rightOp, joinType,
Option(pushDownPredicate), hint))
+ if (stayUp.isEmpty) newPlan else Filter(stayUp.reduce(And), newPlan)
+ } else {
+ // The join condition is not a subset of the Window's PARTITION BY
clause,
+ // no push down.
+ join
+ }
+ }
+
+ // Similar to the above Filter over Union
+ // LeftSemi/LeftAnti over Union
+ case join @ Join(union: Union, rightOp, LeftSemiOrAnti(joinType),
joinCond, hint)
+ if canPushThroughCondition(union.children, joinCond, rightOp) =>
+ if (joinCond.isEmpty) {
+ // Push down the Join below Union
+ val newGrandChildren = union.children.map { grandchild =>
+ Join(grandchild, rightOp, joinType, joinCond, hint)
+ }
+ union.withNewChildren(newGrandChildren)
+ } else {
+ val pushDown = splitConjunctivePredicates(joinCond.get)
+
+ if (pushDown.nonEmpty) {
+ val pushDownCond = pushDown.reduceLeft(And)
+ val output = union.output
+ val newGrandChildren = union.children.map { grandchild =>
+ val newCond = pushDownCond transform {
+ case e if output.exists(_.semanticEquals(e)) =>
+ grandchild.output(output.indexWhere(_.semanticEquals(e)))
+ }
+ assert(newCond.references.subsetOf(grandchild.outputSet ++
rightOp.outputSet))
+ Join(grandchild, rightOp, joinType, Option(newCond), hint)
+ }
+ union.withNewChildren(newGrandChildren)
+ } else {
+ // Nothing to push down
+ join
+ }
+ }
+
+ // Similar to the above Filter over UnaryNode
+ // LeftSemi/LeftAnti over UnaryNode
+ case join @ Join(u: UnaryNode, rightOp, LeftSemiOrAnti(joinType),
joinCond, hint)
+ if PushDownPredicate.canPushThrough(u) =>
+ pushDownJoin(join, u.child) { joinCond =>
+ u.withNewChildren(Seq(Join(u.child, rightOp, joinType,
Option(joinCond), hint)))
+ }
+ }
+
+ /**
+ * Check if we can safely push a join through a project or union by making
sure that predicate
+ * subqueries in the condition do not contain the same attributes as the
plan they are moved
+ * into. This can happen when the plan and predicate subquery have the same
source.
+ */
+ private def canPushThroughCondition(plans: Seq[LogicalPlan], condition:
Option[Expression],
+ rightOp: LogicalPlan): Boolean = {
+ val attributes = AttributeSet(plans.flatMap (_.output))
+ if (condition.isDefined) {
+ val matched =
condition.get.references.intersect(rightOp.outputSet).intersect(attributes)
+ matched.isEmpty
+ } else true
+ }
+
+
+ private def pushDownJoin(
+ join: Join,
+ grandchild: LogicalPlan)(insertFilter: Expression => LogicalPlan):
LogicalPlan = {
+ // Only push down the join when join condition deterministic and all the
referenced attributes
+ // come from childen of left and right legs of join.
+ val (candidates, containingNonDeterministic) = if
(join.condition.isDefined) {
+ splitConjunctivePredicates(join.condition.get).partition(_.deterministic)
+ } else {
+ (Nil, Nil)
+ }
+
+ val (pushDown, rest) = candidates.partition { cond =>
+ cond.references.subsetOf(grandchild.outputSet ++ join.right.outputSet)
+ }
+
+ val stayUp = rest ++ containingNonDeterministic
+
+ if (pushDown.nonEmpty) {
+ val newChild = insertFilter(pushDown.reduceLeft(And))
+ if (stayUp.nonEmpty) {
+ Filter(stayUp.reduceLeft(And), newChild)
+ } else {
+ newChild
+ }
+ } else {
+ join
+ }
+ }
+
Review comment:
remove this empty line
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