HeartSaVioR commented on a change in pull request #31987: URL: https://github.com/apache/spark/pull/31987#discussion_r655987301
########## File path: sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/MergingSessionsIterator.scala ########## @@ -0,0 +1,254 @@ +/* + * 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 findNextPartition = 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 (!findNextPartition && 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 group. + findNextPartition = true + startNewSession(currentRow, groupingKey, sessionStruct) + } + } else { + // We find a new group. + findNextPartition = 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 (!findNextPartition) { + 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) + } + + def updateSessionEnd(sessionStruct: UnsafeRow, sessionEnd: Long): Unit = { + sessionStruct.setLong(1, sessionEnd) + } + + private def expandEndOfCurrentSession(sessionEnd: Long): Unit = { Review comment: Let's refrain `processCurrentSortedGroup` to deal with session struct directly. It'd be odd if we use functions to get the value but directly set it. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
