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From fhueske <...@git.apache.org>
Subject [GitHub] flink pull request #3550: [FLINK-5654] - Add processing time OVER RANGE BETW...
Date Mon, 20 Mar 2017 22:07:16 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3550#discussion_r107023949
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/aggregate/DataStreamProcTimeAggregateWindowFunction.scala
---
    @@ -0,0 +1,108 @@
    +/*
    + * 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.table.runtime.aggregate
    +
    +import java.lang.Iterable
    +
    +import org.apache.flink.api.java.tuple.Tuple
    +import org.apache.flink.types.Row
    +import org.apache.flink.configuration.Configuration
    +import org.apache.flink.streaming.api.functions.windowing.RichWindowFunction
    +import org.apache.flink.streaming.api.windowing.windows.Window
    +import org.apache.flink.util.Collector
    +import org.apache.flink.table.functions.AggregateFunction
    +import org.apache.flink.table.functions.Accumulator
    +
    +/**
    +  * Computes the final aggregate value from incrementally computed aggreagtes.
    +  *
    +  * @param aggregates The aggregates to be computed
    +  * @param aggFields the fields on which to apply the aggregate.
    +  * @param forwardedFieldCount The fields to be carried from current row.
    +  */
    +class DataStreamProcTimeAggregateWindowFunction[W <: Window](
    +     private val aggregates: Array[AggregateFunction[_]],
    +     private val aggFields: Array[Int],
    +     private val forwardedFieldCount: Int)
    +  extends RichWindowFunction[Row, Row, Tuple, W] {
    +
    +private var output: Row = _
    +private var accumulators: Row= _
    +
    +  override def open(parameters: Configuration): Unit = {
    +     output = new Row(forwardedFieldCount + aggregates.length)
    +     accumulators = new Row(aggregates.length)
    +     var i = 0
    +     while (i < aggregates.length) {
    +        accumulators.setField(i, aggregates(i).createAccumulator())
    +        i = i + 1
    +     }
    +  }
    +  
    + 
    +  /**
    +    * Calculate aggregated values output by aggregate buffer, and set them into output
    +    * Row based on the mapping relation between intermediate aggregate data and output
data.
    +    */
    +  override def apply(
    +      key: Tuple,
    +      window: W,
    +      records: Iterable[Row],
    +      out: Collector[Row]): Unit = {
    +
    +     var i = 0
    +     //initialize the values of the aggregators by re-creating them
    +     //the design of the Accumulator interface should be extended to enable 
    +     //a reset function for better performance
    +     while (i < aggregates.length) {
    +       aggregates(i).resetAccumulator(accumulators.getField(i).asInstanceOf[Accumulator])
    +       i += 1
    +     }
    +   
    +     var reuse:Row = null
    +     //iterate through the elements and aggregate
    +     val iter = records.iterator
    +     while (iter.hasNext) {
    +       reuse = iter.next
    +       i = 0
    +       while (i < aggregates.length) {
    +          val accumulator = accumulators.getField(i).asInstanceOf[Accumulator]
    +          aggregates(i).accumulate(accumulator, reuse.getField(aggFields(i)))
    +          i += 1
    +       }
    +     }
    +
    +    //set the values of the result with current elements values if needed
    --- End diff --
    
    why `if needed`?


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