org.apache.spark.sql.execution.Expand.scala Maven / Gradle / Ivy

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/*
 * 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.rdd.RDD
import org.apache.spark.sql.catalyst.InternalRow
import org.apache.spark.sql.catalyst.errors._
import org.apache.spark.sql.catalyst.expressions._
import org.apache.spark.sql.catalyst.plans.physical.{Partitioning, UnknownPartitioning}

/**
 * Apply the all of the GroupExpressions to every input row, hence we will get
 * multiple output rows for a input row.
 * @param projections The group of expressions, all of the group expressions should
 *                    output the same schema specified bye the parameter `output`
 * @param output      The output Schema
 * @param child       Child operator
 */
case class Expand(
    projections: Seq[Seq[Expression]],
    output: Seq[Attribute],
    child: SparkPlan)
  extends UnaryNode {

  // The GroupExpressions can output data with arbitrary partitioning, so set it
  // as UNKNOWN partitioning
  override def outputPartitioning: Partitioning = UnknownPartitioning(0)

  override def outputsUnsafeRows: Boolean = child.outputsUnsafeRows
  override def canProcessUnsafeRows: Boolean = true
  override def canProcessSafeRows: Boolean = true

  override def references: AttributeSet =
    AttributeSet(projections.flatten.flatMap(_.references))

  private[this] val projection = {
    if (outputsUnsafeRows) {
      (exprs: Seq[Expression]) => UnsafeProjection.create(exprs, child.output)
    } else {
      (exprs: Seq[Expression]) => newMutableProjection(exprs, child.output)()
    }
  }

  protected override def doExecute(): RDD[InternalRow] = attachTree(this, "execute") {
    child.execute().mapPartitions { iter =>
      val groups = projections.map(projection).toArray
      new Iterator[InternalRow] {
        private[this] var result: InternalRow = _
        private[this] var idx = -1  // -1 means the initial state
        private[this] var input: InternalRow = _

        override final def hasNext: Boolean = (-1 < idx && idx < groups.length) || iter.hasNext

        override final def next(): InternalRow = {
          if (idx <= 0) {
            // in the initial (-1) or beginning(0) of a new input row, fetch the next input tuple
            input = iter.next()
            idx = 0
          }

          result = groups(idx)(input)
          idx += 1

          if (idx == groups.length && iter.hasNext) {
            idx = 0
          }

          result
        }
      }
    }
  }
}