cloud-fan 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_r258388226
########## File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/PushDownLeftSemiAntiJoin.scala ########## @@ -0,0 +1,191 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.spark.sql.catalyst.optimizer + +import org.apache.spark.sql.catalyst.expressions._ +import org.apache.spark.sql.catalyst.plans._ +import org.apache.spark.sql.catalyst.plans.logical._ +import org.apache.spark.sql.catalyst.rules.Rule + +/** + * This rule is a variant of [[PushDownPredicate]] which can handle + * pushing down Left semi and Left Anti joins below the following operators. + * 1) Project + * 2) Window + * 3) Union + * 4) Aggregate + * 5) Other permissible unary operators. please see [[PushDownPredicate.canPushThrough]]. + */ +object PushDownLeftSemiAntiJoin extends Rule[LogicalPlan] with PredicateHelper { + def apply(plan: LogicalPlan): LogicalPlan = plan transform { + // LeftSemi/LeftAnti over Project + case Join(p @ Project(pList, gChild), rightOp, LeftSemiOrAnti(joinType), joinCond, hint) + if pList.forall(_.deterministic) && + !pList.exists(ScalarSubquery.hasScalarSubquery)&& + canPushThroughCondition(Seq(gChild), joinCond, rightOp) => + if (joinCond.isEmpty) { + // No join condition, just push down the Join below Project + p.copy(child = Join(gChild, rightOp, joinType, joinCond, hint)) + } else { + val aliasMap = PushDownPredicate.getAliasMap(p) + val newJoinCond = if (aliasMap.nonEmpty) { + Option(replaceAlias(joinCond.get, aliasMap)) + } else { + joinCond + } + p.copy(child = Join(gChild, rightOp, joinType, newJoinCond, hint)) + } + + // LeftSemi/LeftAnti over Aggregate + case join @ Join(agg: Aggregate, rightOp, LeftSemiOrAnti(joinType), joinCond, hint) + if agg.aggregateExpressions.forall(_.deterministic) && agg.groupingExpressions.nonEmpty => + if (joinCond.isEmpty) { + // No join condition, just push down Join below Aggregate + agg.copy(child = Join(agg.child, rightOp, joinType, joinCond, hint)) + } else { + val aliasMap = PushDownPredicate.getAliasMap(agg) + + // 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(agg.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 newAgg = agg.copy(child = Join(agg.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) newAgg else Filter(stayUp.reduce(And), newAgg) + } else { + // The join condition is not a subset of the Aggregate's GROUP BY columns, + // no push down. + join + } + } + + // 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 predicate = pushDown.reduce(And) + val newPlan = w.copy(child = Join(w.child, rightOp, joinType, Option(predicate), 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 + } + } + + // 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 { Join(_, 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 + } + } + + // LeftSemi/LeftAnti over UnaryNode + case join @ Join(u: UnaryNode, rightOp, LeftSemiOrAnti(joinType), joinCond, hint) + if PushDownPredicate.canPushThrough(u) && u.expressions.forall(_.deterministic) => + 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 attributes + * referred in join 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, Review comment: 4 space indentation. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. 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