[GitHub] spark pull request: [SPARK-10215] [SQL] Fix precision of division ...

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

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

    https://github.com/apache/spark/pull/8415#discussion_r47203695
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala ---
    @@ -400,8 +400,15 @@ object HiveTypeCoercion {
                 resultType)
     
             case Divide(e1 @ DecimalType.Expression(p1, s1), e2 @ DecimalType.Expression(p2, s2)) =>
    -          val resultType = DecimalType.bounded(p1 - s1 + s2 + max(6, s1 + p2 + 1),
    -            max(6, s1 + p2 + 1))
    +          var intDig = min(DecimalType.MAX_SCALE, p1 - s1 + s2)
    +          var decDig = min(DecimalType.MAX_SCALE, max(6, s1 + p2 + 1))
    +          val diff = (intDig + decDig) - DecimalType.MAX_SCALE
    +          if (diff > 0) {
    +            decDig -= diff / 2 + 1
    +            intDig = DecimalType.MAX_SCALE - decDig
    +            DecimalType.bounded(intDig + decDig, decDig)
    +          }
    +          val resultType = DecimalType.bounded(intDig + decDig, decDig)
               val widerType = widerDecimalType(p1, s1, p2, s2)
    --- End diff --
    
    is the `resultType` always tighter than `widerType`?


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