Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/9556#discussion_r44351639
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/Count.scala
---
@@ -32,23 +32,34 @@ case class Count(child: Expression) extends
DeclarativeAggregate {
// Expected input data type.
override def inputTypes: Seq[AbstractDataType] = Seq(AnyDataType)
- private val count = AttributeReference("count", LongType)()
+ private lazy val count = AttributeReference("count", LongType)()
- override val aggBufferAttributes = count :: Nil
+ override lazy val aggBufferAttributes = count :: Nil
- override val initialValues = Seq(
+ override lazy val initialValues = Seq(
/* count = */ Literal(0L)
)
- override val updateExpressions = Seq(
+ override lazy val updateExpressions = Seq(
/* count = */ If(IsNull(child), count, count + 1L)
)
- override val mergeExpressions = Seq(
+ override lazy val mergeExpressions = Seq(
/* count = */ count.left + count.right
)
- override val evaluateExpression = Cast(count, LongType)
+ override lazy val evaluateExpression = Cast(count, LongType)
override def defaultResult: Option[Literal] = Option(Literal(0L))
}
+
+object Count {
+ def apply(children: Seq[Expression]): Count = {
--- End diff --
Maybe document what is going on here.
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