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From wuchong <...@git.apache.org>
Subject [GitHub] flink pull request #2792: [FLINK-4937] [Table] Add incremental group window ...
Date Sat, 19 Nov 2016 11:54:33 GMT
Github user wuchong commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2792#discussion_r88778110
  
    --- 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] {
    +
    +  Preconditions.checkNotNull(aggregates)
    +  Preconditions.checkNotNull(groupKeysMapping)
    +  @transient var accumulatorRow:Row = _
    +
    +  /**
    +    * For Incremental intermediate aggregate Rows, merge value1 and value2
    +    * into aggregate buffer, return aggregate buffer.
    +    *
    +    * @param value1 The first value to combined.
    +    * @param value2 The second value to combined.
    +    * @return The combined value of both input values.
    +    *
    +    */
    +  override def reduce(value1: Row, value2: Row): Row = {
    +
    +    if(null == accumulatorRow){
    +      accumulatorRow = new Row(intermediateRowArity)
    +    }
    +
    +    // Initiate intermediate aggregate value.
    +    aggregates.foreach(_.initiate(accumulatorRow))
    --- End diff --
    
    Could we merge `value2` into `value1` and return `value1` ? So that the `accumulatorRow`
could be left out.


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