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From cloud-fan <...@git.apache.org>
Subject [GitHub] spark pull request #17138: [SPARK-17080] [SQL] join reorder
Date Fri, 03 Mar 2017 23:48:21 GMT
Github user cloud-fan commented on a diff in the pull request:

    https://github.com/apache/spark/pull/17138#discussion_r104265487
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/CostBasedJoinReorder.scala
---
    @@ -0,0 +1,274 @@
    +/*
    + * 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 scala.collection.mutable
    +
    +import org.apache.spark.sql.catalyst.CatalystConf
    +import org.apache.spark.sql.catalyst.expressions.{And, AttributeSet, Expression, PredicateHelper}
    +import org.apache.spark.sql.catalyst.plans.{Inner, InnerLike}
    +import org.apache.spark.sql.catalyst.plans.logical.{Join, LogicalPlan, Project}
    +import org.apache.spark.sql.catalyst.rules.Rule
    +
    +
    +/**
    + * Cost-based join reorder.
    + * We may have several join reorder algorithms in the future. This class is the entry
of these
    + * algorithms, and chooses which one to use.
    + */
    +case class CostBasedJoinReorder(conf: CatalystConf) extends Rule[LogicalPlan] with PredicateHelper
{
    +  def apply(plan: LogicalPlan): LogicalPlan = {
    +    if (!conf.cboEnabled || !conf.joinReorderEnabled) {
    +      plan
    +    } else {
    +      plan transform {
    +        case p @ Project(projectList, j @ Join(_, _, _: InnerLike, _)) if !j.ordered
=>
    +          reorder(j, p.outputSet)
    +        case j @ Join(_, _, _: InnerLike, _) if !j.ordered =>
    +          reorder(j, j.outputSet)
    +      }
    +    }
    +  }
    +
    +  def reorder(plan: LogicalPlan, output: AttributeSet): LogicalPlan = {
    +    val (items, conditions) = extractInnerJoins(plan)
    +    val result =
    +      if (items.size > 2 && items.size <= conf.joinReorderDPThreshold &&
conditions.nonEmpty) {
    +        JoinReorderDP(conf, items, conditions, output).search().getOrElse(plan)
    +      } else {
    +        plan
    +      }
    +    // Set all inside joins ordered.
    +    setOrdered(result)
    +    result
    +  }
    +
    +  /**
    +   * Extract inner joinable items and join conditions.
    +   * This method works for bushy trees and left/right deep trees.
    +   */
    +  def extractInnerJoins(plan: LogicalPlan): (Seq[LogicalPlan], Set[Expression]) = plan
match {
    +    case j @ Join(left, right, _: InnerLike, cond) =>
    +      val (leftPlans, leftConditions) = extractInnerJoins(left)
    +      val (rightPlans, rightConditions) = extractInnerJoins(right)
    +      (leftPlans ++ rightPlans, cond.map(splitConjunctivePredicates).getOrElse(Nil).toSet
++
    +        leftConditions ++ rightConditions)
    +    case Project(_, j @ Join(left, right, _: InnerLike, cond)) =>
    --- End diff --
    
    I think we should assume the project list expressions are all attribute


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