cloud-fan commented on a change in pull request #29026:
URL: https://github.com/apache/spark/pull/29026#discussion_r451257595
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/Sum.scala
##########
@@ -58,39 +58,50 @@ case class Sum(child: Expression) extends
DeclarativeAggregate with ImplicitCast
case _ => DoubleType
}
- private lazy val sumDataType = resultType
-
- private lazy val sum = AttributeReference("sum", sumDataType)()
+ private lazy val sum = AttributeReference("sum", resultType)()
private lazy val isEmpty = AttributeReference("isEmpty", BooleanType,
nullable = false)()
- private lazy val zero = Literal.default(sumDataType)
+ private lazy val zero = Literal.default(resultType)
override lazy val aggBufferAttributes = resultType match {
case _: DecimalType => sum :: isEmpty :: Nil
case _ => sum :: Nil
}
override lazy val initialValues: Seq[Expression] = resultType match {
- case _: DecimalType => Seq(Literal(null, resultType), Literal(true,
BooleanType))
+ case _: DecimalType => Seq(zero, Literal(true, BooleanType))
case _ => Seq(Literal(null, resultType))
}
override lazy val updateExpressions: Seq[Expression] = {
- if (child.nullable) {
- val updateSumExpr = coalesce(coalesce(sum, zero) +
child.cast(sumDataType), sum)
- resultType match {
- case _: DecimalType =>
- Seq(updateSumExpr, isEmpty && child.isNull)
- case _ => Seq(updateSumExpr)
- }
- } else {
- val updateSumExpr = coalesce(sum, zero) + child.cast(sumDataType)
- resultType match {
- case _: DecimalType =>
- Seq(updateSumExpr, Literal(false, BooleanType))
- case _ => Seq(updateSumExpr)
- }
+ resultType match {
+ case _: DecimalType =>
+ // For decimal type, the initial value of `sum` is 0. We need to keep
`sum` unchanged if
+ // the input is null, as SUM function ignores null input. The `sum`
can only be null if
+ // overflow happens under non-ansi mode.
Review comment:
It's the `Add` expression, and it always respects the ansi mode, no
matter it's in update or merge expression.
This makes sense. If overflow happens, we will fail anyway. It's better to
fail earlier to save resources.
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