[GitHub] spark pull request #17075: [SPARK-19727][SQL] Fix for round function that mo...

[cloud-fan <gi...@git.apache.org>]

Github user cloud-fan commented on a diff in the pull request:

    https://github.com/apache/spark/pull/17075#discussion_r103588610
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala ---
    @@ -339,36 +339,34 @@ case class Cast(child: Expression, dataType: DataType, timeZoneId: Option[String
       }
     
       /**
    -   * Change the precision / scale in a given decimal to those set in `decimalType` (if any),
    -   * returning null if it overflows or modifying `value` in-place and returning it if successful.
    +   * Create new `Decimal` with precision and scale given in `decimalType` (if any),
    +   * returning null if it overflows or creating a new `value` and returning it if successful.
        *
    -   * NOTE: this modifies `value` in-place, so don't call it on external data.
        */
    -  private[this] def changePrecision(value: Decimal, decimalType: DecimalType): Decimal = {
    -    if (value.changePrecision(decimalType.precision, decimalType.scale)) value else null
    -  }
    +  private[this] def toPrecision(value: Decimal, decimalType: DecimalType): Decimal =
    +    value.toPrecision(decimalType.precision, decimalType.scale).orNull
     
       private[this] def castToDecimal(from: DataType, target: DecimalType): Any => Any = from match {
         case StringType =>
           buildCast[UTF8String](_, s => try {
    -        changePrecision(Decimal(new JavaBigDecimal(s.toString)), target)
    +        toPrecision(Decimal(new JavaBigDecimal(s.toString)), target)
    --- End diff --
    
    Looks like here we don't need to create a new instance?


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