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ASF GitHub Bot commented on FLINK-4937: --------------------------------------- Github user fhueske commented on a diff in the pull request: https://github.com/apache/flink/pull/2792#discussion_r88638112 --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/runtime/aggregate/IncrementalAggregateReduceFunction.scala --- @@ -0,0 +1,69 @@ +/* + * 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.flink.api.table.runtime.aggregate + +import org.apache.flink.api.common.functions.ReduceFunction +import org.apache.flink.api.table.Row +import org.apache.flink.util.Preconditions + +/** + * For Incremental intermediate aggregate Rows, merge every row into aggregate buffer. + * + * @param aggregates The aggregate functions. + * @param groupKeysMapping The index mapping of group keys between intermediate aggregate Row + * and output Row. + */ +class IncrementalAggregateReduceFunction( + private val aggregates: Array[Aggregate[_]], + private val groupKeysMapping: Array[(Int, Int)], + private val intermediateRowArity: Int)extends ReduceFunction[Row] { --- End diff -- add space before `extends` > Add incremental group window aggregation for streaming Table API > ---------------------------------------------------------------- > > Key: FLINK-4937 > URL: https://issues.apache.org/jira/browse/FLINK-4937 > Project: Flink > Issue Type: Sub-task > Components: Table API & SQL > Affects Versions: 1.2.0 > Reporter: Fabian Hueske > Assignee: sunjincheng > > Group-window aggregates for streaming tables are currently not done in an > incremental fashion. This means that the window collects all records and > performs the aggregation when the window is closed instead of eagerly > updating a partial aggregate for every added record. Since records are > buffered, non-incremental aggregation requires more storage space than > incremental aggregation. > The DataStream API which is used under the hood of the streaming Table API > features [incremental > aggregation|https://ci.apache.org/projects/flink/flink-docs-release-1.2/dev/windows.html#windowfunction-with-incremental-aggregation] > using a {{ReduceFunction}}. > We should add support for incremental aggregation in group-windows. > This is a follow-up task of FLINK-4691. -- This message was sent by Atlassian JIRA (v6.3.4#6332)