From 87e474128f30dc93fd1d1e831408d763d3913178 Mon Sep 17 00:00:00 2001 From: Reynold Xin Date: Thu, 4 Jun 2015 01:20:30 -0700 Subject: [PATCH] [SPARK-7440][SQL] Remove physical Distinct operator in favor of Aggregate. Distinct is very similar to Aggregate, which is an important operator to optimize for. This patch replaces Distinct with Aggregate in the optimizer, so Distinct will become more efficient over time as we optimize Aggregate. --- .../sql/catalyst/optimizer/Optimizer.scala | 11 +++++ .../plans/logical/basicOperators.scala | 3 ++ .../ReplaceDistinctWithAggregateSuite.scala | 42 +++++++++++++++++++ .../org/apache/spark/sql/DataFrame.scala | 2 +- .../spark/sql/execution/SparkStrategies.scala | 4 +- .../spark/sql/execution/basicOperators.scala | 31 -------------- 6 files changed, 59 insertions(+), 34 deletions(-) create mode 100644 sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ReplaceDistinctWithAggregateSuite.scala diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala index 5c6379b8d44b0..4747c3ba29a04 100644 --- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala +++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala @@ -36,6 +36,8 @@ object DefaultOptimizer extends Optimizer { // SubQueries are only needed for analysis and can be removed before execution. Batch("Remove SubQueries", FixedPoint(100), EliminateSubQueries) :: + Batch("Distinct", FixedPoint(100), + ReplaceDistinctWithAggregate) :: Batch("Operator Reordering", FixedPoint(100), UnionPushdown, CombineFilters, @@ -696,3 +698,12 @@ object ConvertToLocalRelation extends Rule[LogicalPlan] { LocalRelation(projectList.map(_.toAttribute), data.map(projection)) } } + +/** + * Replaces logical [[Distinct]] operator with an [[Aggregate]] operator. + */ +object ReplaceDistinctWithAggregate extends Rule[LogicalPlan] { + def apply(plan: LogicalPlan): LogicalPlan = plan transform { + case Distinct(child) => Aggregate(child.output, child.output, child) + } +} diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicOperators.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicOperators.scala index 33a9e55a47dee..e77e5c27b687a 100644 --- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicOperators.scala +++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicOperators.scala @@ -339,6 +339,9 @@ case class Sample( override def output: Seq[Attribute] = child.output } +/** + * Returns a new logical plan that dedups input rows. + */ case class Distinct(child: LogicalPlan) extends UnaryNode { override def output: Seq[Attribute] = child.output } diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ReplaceDistinctWithAggregateSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ReplaceDistinctWithAggregateSuite.scala new file mode 100644 index 0000000000000..df29a62ff0e15 --- /dev/null +++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ReplaceDistinctWithAggregateSuite.scala @@ -0,0 +1,42 @@ +/* + * 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.dsl.plans._ +import org.apache.spark.sql.catalyst.dsl.expressions._ +import org.apache.spark.sql.catalyst.plans.PlanTest +import org.apache.spark.sql.catalyst.plans.logical.{Aggregate, Distinct, LocalRelation, LogicalPlan} +import org.apache.spark.sql.catalyst.rules.RuleExecutor + +class ReplaceDistinctWithAggregateSuite extends PlanTest { + + object Optimize extends RuleExecutor[LogicalPlan] { + val batches = Batch("ProjectCollapsing", Once, ReplaceDistinctWithAggregate) :: Nil + } + + test("replace distinct with aggregate") { + val input = LocalRelation('a.int, 'b.int) + + val query = Distinct(input) + val optimized = Optimize.execute(query.analyze) + + val correctAnswer = Aggregate(input.output, input.output, input) + + comparePlans(optimized, correctAnswer) + } +} diff --git a/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala b/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala index 034d887901975..ece2749fdc10b 100644 --- a/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala +++ b/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala @@ -1295,7 +1295,7 @@ class DataFrame private[sql]( * @group dfops * @since 1.3.0 */ - override def distinct: DataFrame = Distinct(logicalPlan) + override def distinct: DataFrame = dropDuplicates() /** * @group basic diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala index d0a1ad00560d3..7a1331a39151a 100644 --- a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala +++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala @@ -284,8 +284,8 @@ private[sql] abstract class SparkStrategies extends QueryPlanner[SparkPlan] { case r: RunnableCommand => ExecutedCommand(r) :: Nil case logical.Distinct(child) => - execution.Distinct(partial = false, - execution.Distinct(partial = true, planLater(child))) :: Nil + throw new IllegalStateException( + "logical distinct operator should have been replaced by aggregate in the optimizer") case logical.Repartition(numPartitions, shuffle, child) => execution.Repartition(numPartitions, shuffle, planLater(child)) :: Nil case logical.SortPartitions(sortExprs, child) => diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/basicOperators.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/basicOperators.scala index a30ade86441ca..fb42072f9d5a7 100644 --- a/sql/core/src/main/scala/org/apache/spark/sql/execution/basicOperators.scala +++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/basicOperators.scala @@ -230,37 +230,6 @@ case class ExternalSort( override def outputOrdering: Seq[SortOrder] = sortOrder } -/** - * :: DeveloperApi :: - * Computes the set of distinct input rows using a HashSet. - * @param partial when true the distinct operation is performed partially, per partition, without - * shuffling the data. - * @param child the input query plan. - */ -@DeveloperApi -case class Distinct(partial: Boolean, child: SparkPlan) extends UnaryNode { - override def output: Seq[Attribute] = child.output - - override def requiredChildDistribution: Seq[Distribution] = - if (partial) UnspecifiedDistribution :: Nil else ClusteredDistribution(child.output) :: Nil - - protected override def doExecute(): RDD[Row] = { - child.execute().mapPartitions { iter => - val hashSet = new scala.collection.mutable.HashSet[Row]() - - var currentRow: Row = null - while (iter.hasNext) { - currentRow = iter.next() - if (!hashSet.contains(currentRow)) { - hashSet.add(currentRow.copy()) - } - } - - hashSet.iterator - } - } -} - /** * :: DeveloperApi :: * Return a new RDD that has exactly `numPartitions` partitions.