Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/10960#discussion_r51533775
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/Corr.scala
---
@@ -29,165 +28,95 @@ import org.apache.spark.sql.types._
* Definition of Pearson correlation can be found at
*
http://en.wikipedia.org/wiki/Pearson_product-moment_correlation_coefficient
*/
-case class Corr(
- left: Expression,
- right: Expression,
- mutableAggBufferOffset: Int = 0,
- inputAggBufferOffset: Int = 0)
- extends ImperativeAggregate {
-
- def this(left: Expression, right: Expression) =
- this(left, right, mutableAggBufferOffset = 0, inputAggBufferOffset = 0)
-
- override def children: Seq[Expression] = Seq(left, right)
+case class Corr(x: Expression, y: Expression) extends DeclarativeAggregate
{
+ override def children: Seq[Expression] = Seq(x, y)
override def nullable: Boolean = true
-
override def dataType: DataType = DoubleType
-
override def inputTypes: Seq[AbstractDataType] = Seq(DoubleType,
DoubleType)
- override def checkInputDataTypes(): TypeCheckResult = {
- if (left.dataType.isInstanceOf[DoubleType] &&
right.dataType.isInstanceOf[DoubleType]) {
- TypeCheckResult.TypeCheckSuccess
+ protected val count = AttributeReference("count", DoubleType, nullable =
false)()
+ protected val xAvg = AttributeReference("xAvg", DoubleType, nullable =
false)()
+ protected val yAvg = AttributeReference("yAvg", DoubleType, nullable =
false)()
+ protected val ck = AttributeReference("ck", DoubleType, nullable =
false)()
+ protected val xMk = AttributeReference("xMk", DoubleType, nullable =
false)()
+ protected val yMk = AttributeReference("yMk", DoubleType, nullable =
false)()
+
+ override val aggBufferAttributes: Seq[AttributeReference] = Seq(count,
xAvg, yAvg, ck, xMk, yMk)
+
+ override val initialValues: Seq[Expression] = Seq(
+ /* count = */ Literal(0.0),
+ /* xAvg = */ Literal(0.0),
+ /* yAvg = */ Literal(0.0),
+ /* ck = */ Literal(0.0),
+ /* xMk = */ Literal(0.0),
+ /* yMk = */ Literal(0.0)
+ )
+
+ override lazy val updateExpressions: Seq[Expression] = {
+ val n = count + Literal(1.0)
--- End diff --
Same argument on `count` and `n` usage. Calling them `n` and `newN` might
be better.
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