spark AliasAwareOutputExpression 源码

spark AliasAwareOutputExpression 代码

文件路径：/sql/core/src/main/scala/org/apache/spark/sql/execution/AliasAwareOutputExpression.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.execution

import org.apache.spark.sql.catalyst.expressions.{Alias, Expression, NamedExpression, SortOrder}
import org.apache.spark.sql.catalyst.plans.physical.{HashPartitioning, Partitioning, PartitioningCollection, UnknownPartitioning}

/**
 * A trait that provides functionality to handle aliases in the `outputExpressions`.
 */
trait AliasAwareOutputExpression extends UnaryExecNode {
  protected def outputExpressions: Seq[NamedExpression]

  private lazy val aliasMap = outputExpressions.collect {
    case a @ Alias(child, _) => child.canonicalized -> a.toAttribute
  }.toMap

  protected def hasAlias: Boolean = aliasMap.nonEmpty

  protected def normalizeExpression(exp: Expression): Expression = {
    exp.transformDown {
      case e: Expression => aliasMap.getOrElse(e.canonicalized, e)
    }
  }
}

/**
 * A trait that handles aliases in the `outputExpressions` to produce `outputPartitioning` that
 * satisfies distribution requirements.
 */
trait AliasAwareOutputPartitioning extends AliasAwareOutputExpression {
  final override def outputPartitioning: Partitioning = {
    val normalizedOutputPartitioning = if (hasAlias) {
      child.outputPartitioning match {
        case e: Expression =>
          normalizeExpression(e).asInstanceOf[Partitioning]
        case other => other
      }
    } else {
      child.outputPartitioning
    }

    flattenPartitioning(normalizedOutputPartitioning).filter {
      case hashPartitioning: HashPartitioning => hashPartitioning.references.subsetOf(outputSet)
      case _ => true
    } match {
      case Seq() => UnknownPartitioning(child.outputPartitioning.numPartitions)
      case Seq(singlePartitioning) => singlePartitioning
      case seqWithMultiplePartitionings => PartitioningCollection(seqWithMultiplePartitionings)
    }
  }

  private def flattenPartitioning(partitioning: Partitioning): Seq[Partitioning] = {
    partitioning match {
      case PartitioningCollection(childPartitionings) =>
        childPartitionings.flatMap(flattenPartitioning)
      case rest =>
        rest +: Nil
    }
  }
}

/**
 * A trait that handles aliases in the `orderingExpressions` to produce `outputOrdering` that
 * satisfies ordering requirements.
 */
trait AliasAwareOutputOrdering extends AliasAwareOutputExpression {
  protected def orderingExpressions: Seq[SortOrder]

  final override def outputOrdering: Seq[SortOrder] = {
    if (hasAlias) {
      orderingExpressions.map(normalizeExpression(_).asInstanceOf[SortOrder])
    } else {
      orderingExpressions
    }
  }
}

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