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From davies <>
Subject [GitHub] spark pull request: [SPARK-14275][SQL] Reimplement TypedAggregateE...
Date Wed, 13 Apr 2016 20:16:57 GMT
Github user davies commented on a diff in the pull request:
    --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/TypedAggregateExpression.scala
    @@ -19,133 +19,153 @@ package org.apache.spark.sql.execution.aggregate
     import scala.language.existentials
    -import org.apache.spark.internal.Logging
     import org.apache.spark.sql.Encoder
    -import org.apache.spark.sql.catalyst.InternalRow
    -import org.apache.spark.sql.catalyst.encoders.{encoderFor, ExpressionEncoder, OuterScopes}
    +import org.apache.spark.sql.catalyst.analysis.{UnresolvedAttribute, UnresolvedDeserializer,
    +import org.apache.spark.sql.catalyst.encoders.encoderFor
     import org.apache.spark.sql.catalyst.expressions._
    -import org.apache.spark.sql.catalyst.expressions.aggregate.ImperativeAggregate
    +import org.apache.spark.sql.catalyst.expressions.aggregate.DeclarativeAggregate
     import org.apache.spark.sql.expressions.Aggregator
     import org.apache.spark.sql.types._
     object TypedAggregateExpression {
    -  def apply[A, B : Encoder, C : Encoder](
    -      aggregator: Aggregator[A, B, C]): TypedAggregateExpression = {
    +  def apply[BUF : Encoder, OUT : Encoder](
    +      aggregator: Aggregator[_, BUF, OUT]): TypedAggregateExpression = {
    +    val bufferEncoder = encoderFor[BUF]
    +    // We will insert the deserializer and function call expression at the bottom of
each serializer
    +    // expression while executing `TypedAggregateExpression`, which means multiply serializer
    +    // expressions will all evaluate the same sub-expression at bottom.  To avoid the
    +    // here we always use one single serializer expression to serialize the buffer object
into a
    +    // single-field row, no matter whether the encoder is flat or not.  We also need
to update the
    +    // deserializer to read in all fields from that single-field row.
    +    // TODO: remove this trick after we have  better integration of subexpression elimination
    --- End diff --
    Can we hold this pr a little bit? let me think of how to do subexpression elimination
in aggregate.

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