HeartSaVioR commented on a change in pull request #31570: URL: https://github.com/apache/spark/pull/31570#discussion_r596641133
########## File path: sql/core/src/main/scala/org/apache/spark/sql/execution/SessionWindowExec.scala ########## @@ -0,0 +1,203 @@ +/* + * 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 scala.collection.mutable + +import org.apache.spark.rdd.RDD +import org.apache.spark.sql.catalyst.InternalRow +import org.apache.spark.sql.catalyst.expressions._ +import org.apache.spark.sql.catalyst.expressions.codegen.GenerateUnsafeProjection +import org.apache.spark.sql.catalyst.plans.physical.{ClusteredDistribution, Distribution, Partitioning} + +/** + * Used for calculating the session window start and end for each row, so this plan requires + * child distributed by sessionSpec and sorted by time column in each part. The value for + * window start is time value of the first row in this window, the value for window end is + * time value of the last row plus the windowGap. + * + * @param windowExpressions session window expression for the exec node. + * @param sessionSpec the partition key of this session window, it is the rest column of + * groupingExpr in parent aggregate node. + * @param windowGap window gap in micro second. + * @param child child plan for this node. + */ +case class SessionWindowExec( + windowExpressions: NamedExpression, + timeColumn: Expression, + sessionSpec: Seq[Expression], + windowGap: Long, + child: SparkPlan) + extends UnaryExecNode { + + override def requiredChildDistribution: Seq[Distribution] = { + ClusteredDistribution(sessionSpec) :: Nil + } + + override def requiredChildOrdering: Seq[Seq[SortOrder]] = + Seq(sessionSpec.map(SortOrder(_, Ascending)) :+ SortOrder(timeColumn, Ascending)) + + override def producedAttributes: AttributeSet = AttributeSet(windowExpressions.toAttribute) + + override def output: Seq[Attribute] = child.output ++ Seq(windowExpressions.toAttribute) + + override def outputPartitioning: Partitioning = child.outputPartitioning + + override def outputOrdering: Seq[SortOrder] = child.outputOrdering + + /** + * Produces the result of the query as an `RDD[InternalRow]` + * + * Overridden by concrete implementations of SparkPlan. + */ + override protected def doExecute(): RDD[InternalRow] = { Review comment: I think it's valid to compare this with UpdatingSessionIterator, which is used to support aggregation with one distinct and technically does the same with this. The major difference between twos looks to be that UpdatingSessionIterator doesn't try to memorize entire parts of row - it only memorizes the value part of row, as key part should be just all same with current session, and when session is closed, it restores the memorized rows with key & value parts. I guess there're pros and cons against twos but not that outstanding, and at least this is simpler, I'm OK to pick this up for the replacement of UpdatingSessionIterator. I'm feeling that MergingSessionsIterator is something we should revisit, but as I said, if we feel that's a blocker on moving forward, I'll take it up after this lands to the codebase. ---------------------------------------------------------------- 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]
