Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/17075#discussion_r103588721
--- 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 --
I think this is the only case we need `toPewcision`
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