Github user wojtek-szymanski commented on a diff in the pull request: https://github.com/apache/spark/pull/17075#discussion_r103863738 --- 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) } catch { case _: NumberFormatException => null }) case BooleanType => - buildCast[Boolean](_, b => changePrecision(if (b) Decimal.ONE else Decimal.ZERO, target)) + buildCast[Boolean](_, b => toPrecision(if (b) Decimal.ONE else Decimal.ZERO, target)) case DateType => buildCast[Int](_, d => null) // date can't cast to decimal in Hive case TimestampType => // Note that we lose precision here. - buildCast[Long](_, t => changePrecision(Decimal(timestampToDouble(t)), target)) + buildCast[Long](_, t => toPrecision(Decimal(timestampToDouble(t)), target)) case dt: DecimalType => - b => changePrecision(b.asInstanceOf[Decimal].clone(), target) --- End diff -- Nope, there is one more here: case BooleanType => buildCast[Boolean](_, b => toPrecision(if (b) Decimal.ONE else Decimal.ZERO, target)) Both, `ONE` and `ZERO` are singletons so changing precision on themselves is not a good idea.
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