[GitHub] [arrow-datafusion] mingmwang commented on pull request #6331: refine decimal multiply, avoid cast to wider type

["mingmwang (via GitHub)" <gi...@apache.org>]

mingmwang commented on PR #6331:
URL: https://github.com/apache/arrow-datafusion/pull/6331#issuecomment-1543398311

   
   ```spark  
   override def resultDecimalType(p1: Int, s1: Int, p2: Int, s2: Int): DecimalType = {
       val resultScale = s1 + s2
       val resultPrecision = p1 + p2 + 1
       if (allowPrecisionLoss) {
         DecimalType.adjustPrecisionScale(resultPrecision, resultScale)
       } else {
         DecimalType.bounded(resultPrecision, resultScale)
       }
     }
   
     private lazy val numeric = TypeUtils.getNumeric(dataType, failOnError)
   
     protected override def nullSafeEval(input1: Any, input2: Any): Any = dataType match {
       case DecimalType.Fixed(precision, scale) =>
         checkDecimalOverflow(numeric.times(input1, input2).asInstanceOf[Decimal], precision, scale)
       case _: IntegerType if failOnError =>
         MathUtils.multiplyExact(
           input1.asInstanceOf[Int],
           input2.asInstanceOf[Int],
           getContextOrNull())
       case _: LongType if failOnError =>
         MathUtils.multiplyExact(
           input1.asInstanceOf[Long],
           input2.asInstanceOf[Long],
           getContextOrNull())
       case _ => numeric.times(input1, input2)
     }
   ```


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