HeartSaVioR commented on a change in pull request #31986:
URL: https://github.com/apache/spark/pull/31986#discussion_r619919740



##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/UpdatingSessionsExec.scala
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@@ -0,0 +1,79 @@
+/*
+ * 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.rdd.RDD
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions.{Ascending, Attribute, 
SortOrder}
+import org.apache.spark.sql.catalyst.plans.physical.{AllTuples, 
ClusteredDistribution, Distribution, Partitioning}
+import org.apache.spark.sql.execution.{SparkPlan, UnaryExecNode}
+
+/**
+ * This node updates the session window spec of each input rows via analyzing 
neighbor rows and
+ * determining rows belong to the same session window. The number of input 
rows remains the same.
+ * This node requires sort on input rows by group keys + the start time of 
session window.
+ *
+ * There are lots of overhead compared to [[MergingSessionsExec]]. Use 
[[MergingSessionsExec]]
+ * instead whenever possible. Use this node only when we cannot apply both 
calculations
+ * determining session windows and aggregating rows in session window 
altogether.
+ *
+ * Refer [[UpdatingSessionsIterator]] for more details.
+ */
+case class UpdatingSessionsExec(
+    keyExpressions: Seq[Attribute],
+    sessionExpression: Attribute,
+    child: SparkPlan) extends UnaryExecNode {
+
+  private val groupWithoutSessionExpression = keyExpressions.filterNot {
+    p => p.semanticEquals(sessionExpression)
+  }
+  private val groupingWithoutSessionAttributes = 
groupWithoutSessionExpression.map(_.toAttribute)
+
+  val childOrdering = Seq((groupingWithoutSessionAttributes ++ 
Seq(sessionExpression))
+    .map(SortOrder(_, Ascending)))
+
+  override protected def doExecute(): RDD[InternalRow] = {
+    val inMemoryThreshold = sqlContext.conf.windowExecBufferInMemoryThreshold
+    val spillThreshold = sqlContext.conf.windowExecBufferSpillThreshold

Review comment:
       Makes sense. Let's have new configs for session window specific.




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