spark ReplaceExceptWithFilter 源码

spark ReplaceExceptWithFilter 代码

文件路径：/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/ReplaceExceptWithFilter.scala

/*
 * 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.annotation.tailrec

import org.apache.spark.sql.catalyst.expressions._
import org.apache.spark.sql.catalyst.plans.logical._
import org.apache.spark.sql.catalyst.rules.Rule
import org.apache.spark.sql.catalyst.trees.TreePattern.EXCEPT


/**
 * If one or both of the datasets in the logical [[Except]] operator are purely transformed using
 * [[Filter]], this rule will replace logical [[Except]] operator with a [[Filter]] operator by
 * flipping the filter condition of the right child.
 * {{{
 *   SELECT a1, a2 FROM Tab1 WHERE a2 = 12 EXCEPT SELECT a1, a2 FROM Tab1 WHERE a1 = 5
 *   ==>  SELECT DISTINCT a1, a2 FROM Tab1 WHERE a2 = 12 AND (a1 is null OR a1 <> 5)
 * }}}
 *
 * Note:
 * Before flipping the filter condition of the right node, we should:
 * 1. Combine all it's [[Filter]].
 * 2. Update the attribute references to the left node;
 * 3. Add a Coalesce(condition, False) (to take into account of NULL values in the condition).
 */
object ReplaceExceptWithFilter extends Rule[LogicalPlan] {

  def apply(plan: LogicalPlan): LogicalPlan = {
    if (!plan.conf.replaceExceptWithFilter) {
      return plan
    }

    plan.transformWithPruning(_.containsPattern(EXCEPT), ruleId) {
      case e @ Except(left, right, false) if isEligible(left, right) =>
        val filterCondition = combineFilters(skipProject(right)).asInstanceOf[Filter].condition
        if (filterCondition.deterministic) {
          transformCondition(left, filterCondition).map { c =>
            Distinct(Filter(Not(c), left))
          }.getOrElse {
            e
          }
        } else {
          e
        }
    }
  }

  private def transformCondition(plan: LogicalPlan, condition: Expression): Option[Expression] = {
    val attributeNameMap: Map[String, Attribute] = plan.output.map(x => (x.name, x)).toMap
    if (condition.references.forall(r => attributeNameMap.contains(r.name))) {
      val rewrittenCondition = condition.transform {
        case a: AttributeReference => attributeNameMap(a.name)
      }
      // We need to consider as False when the condition is NULL, otherwise we do not return those
      // rows containing NULL which are instead filtered in the Except right plan
      Some(Coalesce(Seq(rewrittenCondition, Literal.FalseLiteral)))
    } else {
      None
    }
  }

  // TODO: This can be further extended in the future.
  private def isEligible(left: LogicalPlan, right: LogicalPlan): Boolean = (left, right) match {
    case (_, right @ (Project(_, _: Filter) | Filter(_, _))) => verifyConditions(left, right)
    case _ => false
  }

  private def verifyConditions(left: LogicalPlan, right: LogicalPlan): Boolean = {
    val leftProjectList = projectList(left)
    val rightProjectList = projectList(right)

    left.output.size == left.output.map(_.name).distinct.size &&
      !left.exists(_.expressions.exists(SubqueryExpression.hasSubquery)) &&
        !right.exists(_.expressions.exists(SubqueryExpression.hasSubquery)) &&
          Project(leftProjectList, nonFilterChild(skipProject(left))).sameResult(
            Project(rightProjectList, nonFilterChild(skipProject(right))))
  }

  private def projectList(node: LogicalPlan): Seq[NamedExpression] = node match {
    case p: Project => p.projectList
    case x => x.output
  }

  private def skipProject(node: LogicalPlan): LogicalPlan = node match {
    case p: Project => p.child
    case x => x
  }

  private def nonFilterChild(plan: LogicalPlan) = plan.find(!_.isInstanceOf[Filter]).getOrElse {
    throw new IllegalStateException("Leaf node is expected")
  }

  private def combineFilters(plan: LogicalPlan): LogicalPlan = {
    @tailrec
    def iterate(plan: LogicalPlan, acc: LogicalPlan): LogicalPlan = {
      if (acc.fastEquals(plan)) acc else iterate(acc, CombineFilters(acc))
    }
    iterate(plan, CombineFilters(plan))
  }
}

相关信息

spark 源码目录

相关文章

spark ComplexTypes 源码

spark CostBasedJoinReorder 源码

spark DecorrelateInnerQuery 源码

spark EliminateResolvedHint 源码

spark InjectRuntimeFilter 源码

spark InlineCTE 源码

spark LimitPushDownThroughWindow 源码

spark MergeScalarSubqueries 源码

spark NestedColumnAliasing 源码

spark NormalizeFloatingNumbers 源码