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From fhueske <...@git.apache.org>
Subject [GitHub] flink pull request #3472: [FLINK-5963] [table] Remove prepare mapper of Data...
Date Sat, 04 Mar 2017 07:39:03 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3472#discussion_r104282353
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/nodes/dataset/DataSetAggregate.scala
---
    @@ -87,47 +89,67 @@ class DataSetAggregate(
     
       override def translateToPlan(tableEnv: BatchTableEnvironment): DataSet[Row] = {
     
    -    val groupingKeys = grouping.indices.toArray
    -
    -    val mapFunction = AggregateUtil.createPrepareMapFunction(
    -      namedAggregates,
    -      grouping,
    -      inputType)
    -
    -    val groupReduceFunction = AggregateUtil.createAggregateGroupReduceFunction(
    -      namedAggregates,
    -      inputType,
    -      rowRelDataType,
    -      grouping,
    -      inGroupingSet)
    +    val (preAgg: Option[DataSetPreAggFunction],
    +          preAggType: Option[TypeInformation[Row]],
    +          finalAgg: GroupReduceFunction[Row, Row]) =
    +      AggregateUtil.createDataSetAggregateFunctions(
    +        namedAggregates,
    +        inputType,
    +        rowRelDataType,
    +        grouping,
    +        inGroupingSet)
     
         val inputDS = getInput.asInstanceOf[DataSetRel].translateToPlan(tableEnv)
     
         val aggString = aggregationToString(inputType, grouping, getRowType, namedAggregates,
Nil)
    -    val prepareOpName = s"prepare select: ($aggString)"
    -    val mappedInput = inputDS.map(mapFunction).name(prepareOpName)
     
         val rowTypeInfo = FlinkTypeFactory.toInternalRowTypeInfo(getRowType).asInstanceOf[RowTypeInfo]
     
    -    if (groupingKeys.length > 0) {
    +    if (grouping.length > 0) {
           // grouped aggregation
           val aggOpName = s"groupBy: (${groupingToString(inputType, grouping)}), " +
             s"select: ($aggString)"
     
    -      mappedInput.asInstanceOf[DataSet[Row]]
    -        .groupBy(groupingKeys: _*)
    -        .reduceGroup(groupReduceFunction)
    -        .returns(rowTypeInfo)
    -        .name(aggOpName)
    +      if (preAgg.isDefined) {
    +        inputDS
    +          // pre-aggregation
    +          .groupBy(grouping: _*)
    +          .combineGroup(preAgg.get)
    +          .returns(preAggType.get)
    +          .name(aggOpName)
    +          // final aggregation
    +          .groupBy(grouping.indices: _*)
    --- End diff --
    
    The pre-aggregation function modifies the schema of rows. It puts all grouping keys first,
followed by all accumulators. Therefore, the following final aggregation needs to group on
the first `n` fields.
    Before, the prepare mapper changed the layout.


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