Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/12067#discussion_r57990083
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/TypedAggregateExpression.scala
---
@@ -149,3 +149,73 @@ case class TypedAggregateExpression(
override def nodeName: String = aggregator.getClass.getSimpleName
}
+
+case class TypedAggregateExpression2(
+ aggregator: Aggregator[Any, Any, Any],
+ inputDeserializer: Expression,
+ inputAttributes: Seq[Attribute],
+ bufferSerializer: Seq[NamedExpression],
+ bufferDeserializer: Expression,
+ bufferClass: Class[_],
+ resultSerializer: Seq[NamedExpression],
+ dataType: DataType) extends DeclarativeAggregate with NonSQLExpression
{
+
+ override def nullable: Boolean = true
+
+ override def children: Seq[Expression] = Nil
+
+ override def inputTypes: Seq[AbstractDataType] = Nil
+
+ private val aggregatorLiteral = Literal.fromObject(aggregator)
+
+ private val bufferType = ObjectType(bufferClass)
+
+ override lazy val aggBufferAttributes: Seq[Attribute] =
bufferSerializer.map(_.toAttribute)
+
+ override lazy val initialValues: Seq[Expression] = {
+ val zero = Literal.create(aggregator.zero, bufferType)
+ bufferSerializer.map(_ transform {
+ case b: BoundReference => zero
+ })
+ }
+
+ override lazy val updateExpressions: Seq[Expression] = {
+ val reduced = Invoke(
+ aggregatorLiteral,
+ "reduce",
+ bufferType,
+ bufferDeserializer :: inputDeserializer :: Nil)
+
+ bufferSerializer.map(_ transform {
+ case b: BoundReference => reduced
--- End diff --
yes, it's the same problem.
turning an object to a struct in one shot doesn't solve the problem, as we
need to flatten it to `Seq[Expression]` here, which will be a list of
`GetStructField` and the "one shot" expression still appears many times.
Actually I think we don't need to do anything here. Although the `reduced`
expression appears many times, they are same references and subexpression
elimination should always work. Or we can introduce the Holder and Reference to
make it more clear.
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