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From: marmbrus <git@git.apache.org>
To: reviews@spark.apache.org
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Subject: [GitHub] spark pull request: [SPARK-9830] [SQL] Remove
 AggregateExpression1...
Content-Type: text/plain
Message-Id: <20151109235833.33C7CE0974@git1-us-west.apache.org>
Date: Mon,  9 Nov 2015 23:58:33 +0000 (UTC)

Github user marmbrus commented on a diff in the pull request:

    https://github.com/apache/spark/pull/9556#discussion_r44352445
  
    --- Diff: sql/core/src/main/scala/org/apache/spark/sql/GroupedData.scala ---
    @@ -88,30 +89,33 @@ class GroupedData protected[sql](
             namedExpr
           }
         }
    -    toDF(columnExprs.map(f))
    +    toDF(columnExprs.map(expr => f(expr).toAggregateExpression()))
       }
     
       private[this] def strToExpr(expr: String): (Expression => Expression) = {
    -    expr.toLowerCase match {
    -      case "avg" | "average" | "mean" => Average
    -      case "max" => Max
    -      case "min" => Min
    -      case "stddev" | "std" => StddevSamp
    -      case "stddev_pop" => StddevPop
    -      case "stddev_samp" => StddevSamp
    -      case "variance" => VarianceSamp
    -      case "var_pop" => VariancePop
    -      case "var_samp" => VarianceSamp
    -      case "sum" => Sum
    -      case "skewness" => Skewness
    -      case "kurtosis" => Kurtosis
    -      case "count" | "size" =>
    -        // Turn count(*) into count(1)
    -        (inputExpr: Expression) => inputExpr match {
    -          case s: Star => Count(Literal(1))
    -          case _ => Count(inputExpr)
    -        }
    +    val exprToFunc: (Expression => AggregateFunction) = {
    +      (inputExpr: Expression) => expr.toLowerCase match {
    +        case "avg" | "average" | "mean" => Average(inputExpr)
    +        case "max" => Max(inputExpr)
    +        case "min" => Min(inputExpr)
    +        case "stddev" | "std" => StddevSamp(inputExpr)
    +        case "stddev_pop" => StddevPop(inputExpr)
    +        case "stddev_samp" => StddevSamp(inputExpr)
    +        case "variance" => VarianceSamp(inputExpr, 0, 0)
    +        case "var_pop" => VariancePop(inputExpr, 0, 0)
    +        case "var_samp" => VarianceSamp(inputExpr, 0, 0)
    +        case "sum" => Sum(inputExpr)
    +        case "skewness" => Skewness(inputExpr, 0, 0)
    +        case "kurtosis" => Kurtosis(inputExpr, 0, 0)
    --- End diff --
    
    This is kinda of a nit, but I think it might be better to rely on the defaults provided by the extra constructor instead of hard coding these here and elsewhere.
    
    Also, is it possible for a user to corrupt query results by specifying their own offsets due to the way we resolve functions?


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