spark MergingSessionsIterator 源码

spark MergingSessionsIterator 代码

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

import org.apache.spark.sql.catalyst.InternalRow
import org.apache.spark.sql.catalyst.expressions.{Attribute, Expression, GenericInternalRow, JoinedRow, MutableProjection, NamedExpression, SpecificInternalRow, UnsafeProjection, UnsafeRow}
import org.apache.spark.sql.catalyst.expressions.aggregate.AggregateExpression
import org.apache.spark.sql.catalyst.expressions.codegen.GenerateUnsafeProjection
import org.apache.spark.sql.execution.metric.SQLMetric

/**
 * This is a variant of SortAggregateIterator which merges the session windows based on the fact
 * input rows are sorted by "group keys + the start time of session window".
 *
 * When merging windows, it also applies aggregations on merged window, which eliminates the
 * necessity on buffering inputs (which requires copying rows) and update the session spec
 * for each input.
 */
class MergingSessionsIterator(
    partIndex: Int,
    groupingExpressions: Seq[NamedExpression],
    sessionExpression: NamedExpression,
    valueAttributes: Seq[Attribute],
    inputIterator: Iterator[InternalRow],
    aggregateExpressions: Seq[AggregateExpression],
    aggregateAttributes: Seq[Attribute],
    initialInputBufferOffset: Int,
    resultExpressions: Seq[NamedExpression],
    newMutableProjection: (Seq[Expression], Seq[Attribute]) => MutableProjection,
    numOutputRows: SQLMetric)
  extends AggregationIterator(
    partIndex,
    groupingExpressions,
    valueAttributes,
    aggregateExpressions,
    aggregateAttributes,
    initialInputBufferOffset,
    resultExpressions,
    newMutableProjection) {

  val groupingWithoutSession: Seq[NamedExpression] =
    groupingExpressions.diff(Seq(sessionExpression))
  val groupingWithoutSessionAttributes: Seq[Attribute] = groupingWithoutSession.map(_.toAttribute)

  /**
   * Creates a new aggregation buffer and initializes buffer values
   * for all aggregate functions.
   */
  private def newBuffer: InternalRow = {
    val bufferSchema = aggregateFunctions.flatMap(_.aggBufferAttributes)
    val bufferRowSize: Int = bufferSchema.length

    val genericMutableBuffer = new GenericInternalRow(bufferRowSize)
    val useUnsafeBuffer = bufferSchema.map(_.dataType).forall(UnsafeRow.isMutable)

    val buffer = if (useUnsafeBuffer) {
      val unsafeProjection =
        UnsafeProjection.create(bufferSchema.map(_.dataType))
      unsafeProjection.apply(genericMutableBuffer)
    } else {
      genericMutableBuffer
    }
    initializeBuffer(buffer)
    buffer
  }

  ///////////////////////////////////////////////////////////////////////////
  // Mutable states for sort based aggregation.
  ///////////////////////////////////////////////////////////////////////////

  // The partition key of the current partition.
  private[this] var currentGroupingKey: UnsafeRow = _

  private[this] var currentSession: UnsafeRow = _

  // The partition key of next partition.
  private[this] var nextGroupingKey: UnsafeRow = _

  private[this] var nextGroupingSession: UnsafeRow = _

  // The first row of next partition.
  private[this] var firstRowInNextGroup: InternalRow = _

  // Indicates if we has new group of rows from the sorted input iterator
  private[this] var sortedInputHasNewGroup: Boolean = false

  // The aggregation buffer used by the sort-based aggregation.
  private[this] val sortBasedAggregationBuffer: InternalRow = newBuffer

  private[this] val groupingWithoutSessionProjection: UnsafeProjection =
    UnsafeProjection.create(groupingWithoutSession, valueAttributes)

  private[this] val sessionProjection: UnsafeProjection =
    UnsafeProjection.create(Seq(sessionExpression), valueAttributes)

  // The flag indicating there's error on iterator, sort precondition is not fulfilled.
  private var errorOnIterator: Boolean = false

  protected def initialize(): Unit = {
    if (inputIterator.hasNext) {
      initializeBuffer(sortBasedAggregationBuffer)
      val inputRow = inputIterator.next()
      nextGroupingKey = groupingWithoutSessionProjection(inputRow).copy()
      val session = sessionProjection(inputRow)
      nextGroupingSession = session.getStruct(0, 2).copy()
      firstRowInNextGroup = inputRow.copy()
      sortedInputHasNewGroup = true
    } else {
      // This inputIter is empty.
      sortedInputHasNewGroup = false
    }
  }

  initialize()

  /** Processes rows in the current group. It will stop when it find a new group. */
  protected def processCurrentSortedGroup(): Unit = {
    currentGroupingKey = nextGroupingKey
    currentSession = nextGroupingSession

    // Now, we will start to find all rows belonging to this group.
    // We create a variable to track if we see the next group.
    var findNextGroup = false
    // firstRowInNextGroup is the first row of this group. We first process it.
    processRow(sortBasedAggregationBuffer, firstRowInNextGroup)

    // The search will stop when we see the next group or there is no
    // input row left in the iter.
    while (!findNextGroup && inputIterator.hasNext) {
      // Get the grouping key.
      val currentRow = inputIterator.next()
      val groupingKey = groupingWithoutSessionProjection(currentRow)

      val session = sessionProjection(currentRow)
      val sessionStruct = session.getStruct(0, 2)
      val sessionStart = getSessionStart(sessionStruct)
      val sessionEnd = getSessionEnd(sessionStruct)

      // Check if the current row belongs the current input row.
      if (currentGroupingKey == groupingKey) {
        if (sessionStart < getSessionStart(currentSession)) {
          errorOnIterator = true
          throw new IllegalStateException("Input iterator is not sorted based on session!")
        } else if (sessionStart <= getSessionEnd(currentSession)) {
          // expanding session length if needed
          expandEndOfCurrentSession(sessionEnd)
          processRow(sortBasedAggregationBuffer, currentRow)
        } else {
          // We find a new session window in the same group.
          findNextGroup = true
          startNewSession(currentRow, groupingKey, sessionStruct)
        }
      } else {
        // We find a new group.
        findNextGroup = true
        startNewSession(currentRow, groupingKey, sessionStruct)
      }
    }

    // We have not seen a new group. It means that there is no new row in the input
    // iter. The current group is the last group of the iter.
    if (!findNextGroup) {
      sortedInputHasNewGroup = false
    }
  }

  private def startNewSession(
      currentRow: InternalRow,
      groupingKey: UnsafeRow,
      sessionStruct: UnsafeRow): Unit = {
    nextGroupingKey = groupingKey.copy()
    nextGroupingSession = sessionStruct.copy()
    firstRowInNextGroup = currentRow.copy()
  }

  private def getSessionStart(sessionStruct: UnsafeRow): Long = {
    sessionStruct.getLong(0)
  }

  private def getSessionEnd(sessionStruct: UnsafeRow): Long = {
    sessionStruct.getLong(1)
  }

  private def expandEndOfCurrentSession(sessionEnd: Long): Unit = {
    if (sessionEnd > getSessionEnd(currentSession)) {
      currentSession.setLong(1, sessionEnd)
    }
  }

  ///////////////////////////////////////////////////////////////////////////
  // Iterator's public methods
  ///////////////////////////////////////////////////////////////////////////

  override final def hasNext: Boolean = {
    if (errorOnIterator) {
      throw new IllegalStateException("The iterator is already corrupted.")
    }
    sortedInputHasNewGroup
  }

  override final def next(): UnsafeRow = {
    if (hasNext) {
      // Process the current group.
      processCurrentSortedGroup()
      // Generate output row for the current group.
      val groupingKey = generateGroupingKey()

      val outputRow = generateOutput(groupingKey, sortBasedAggregationBuffer)
      // Initialize buffer values for the next group.
      initializeBuffer(sortBasedAggregationBuffer)
      numOutputRows += 1
      outputRow
    } else {
      // no more result
      throw new NoSuchElementException
    }
  }

  private val join = new JoinedRow

  private val groupingKeyProj = GenerateUnsafeProjection.generate(groupingExpressions,
    groupingWithoutSessionAttributes :+ sessionExpression.toAttribute)

  private def generateGroupingKey(): UnsafeRow = {
    val sessionStruct = new SpecificInternalRow(Seq(sessionExpression.toAttribute).toStructType)
    sessionStruct.update(0, currentSession)
    val joined = join(currentGroupingKey, sessionStruct)

    groupingKeyProj(joined)
  }

  def outputForEmptyGroupingKeyWithoutInput(): UnsafeRow = {
    initializeBuffer(sortBasedAggregationBuffer)
    generateOutput(UnsafeRow.createFromByteArray(0, 0), sortBasedAggregationBuffer)
  }
}

相关信息

spark 源码目录

相关文章

spark AggUtils 源码

spark AggregateCodegenSupport 源码

spark AggregationIterator 源码

spark BaseAggregateExec 源码

spark HashAggregateExec 源码

spark HashMapGenerator 源码

spark MergingSessionsExec 源码

spark ObjectAggregationIterator 源码

spark ObjectAggregationMap 源码

spark ObjectHashAggregateExec 源码