Github user viirya commented on a diff in the pull request:
https://github.com/apache/spark/pull/8587#discussion_r43453305
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/functions.scala
---
@@ -524,6 +525,116 @@ case class Sum(child: Expression) extends
DeclarativeAggregate {
override val evaluateExpression = Cast(currentSum, resultType)
}
+case class Corr(
+ left: Expression,
+ right: Expression,
+ mutableAggBufferOffset: Int = 0,
+ inputAggBufferOffset: Int = 0)
+ extends ImperativeAggregate {
+
+ def children: Seq[Expression] = Seq(left, right)
+
+ def nullable: Boolean = false
+
+ def dataType: DataType = DoubleType
+
+ def inputTypes: Seq[AbstractDataType] = Seq(DoubleType)
+
+ def aggBufferSchema: StructType =
StructType.fromAttributes(aggBufferAttributes)
+
+ def inputAggBufferAttributes: Seq[AttributeReference] =
aggBufferAttributes.map(_.newInstance())
+
+ val aggBufferAttributes: Seq[AttributeReference] = Seq(
+ AttributeReference("xAvg", DoubleType)(),
+ AttributeReference("yAvg", DoubleType)(),
+ AttributeReference("Ck", DoubleType)(),
+ AttributeReference("MkX", DoubleType)(),
+ AttributeReference("MkY", DoubleType)(),
+ AttributeReference("count", LongType)())
+
+ override def withNewMutableAggBufferOffset(newMutableAggBufferOffset:
Int): ImperativeAggregate =
+ copy(mutableAggBufferOffset = newMutableAggBufferOffset)
+
+ override def withNewInputAggBufferOffset(newInputAggBufferOffset: Int):
ImperativeAggregate =
+ copy(inputAggBufferOffset = newInputAggBufferOffset)
+
+ override def initialize(buffer: MutableRow): Unit = {
+ (0 until 5).map(idx => buffer.setDouble(mutableAggBufferOffset + idx,
0.0))
+ buffer.setLong(mutableAggBufferOffset + 5, 0L)
+ }
+
+ override def update(buffer: MutableRow, input: InternalRow): Unit = {
+ val x = left.eval(input).asInstanceOf[Double]
+ val y = right.eval(input).asInstanceOf[Double]
+
+ var xAvg = buffer.getDouble(mutableAggBufferOffset)
+ var yAvg = buffer.getDouble(mutableAggBufferOffset + 1)
+ var Ck = buffer.getDouble(mutableAggBufferOffset + 2)
+ var MkX = buffer.getDouble(mutableAggBufferOffset + 3)
+ var MkY = buffer.getDouble(mutableAggBufferOffset + 4)
+ var count = buffer.getLong(mutableAggBufferOffset + 5)
+
+ val deltaX = x - xAvg
+ val deltaY = y - yAvg
+ count += 1
+ xAvg += deltaX / count
+ yAvg += deltaY / count
+ Ck += deltaX * (y - yAvg)
+ MkX += deltaX * (x - xAvg)
+ MkY += deltaY * (y - yAvg)
+
+ buffer.setDouble(mutableAggBufferOffset, xAvg)
+ buffer.setDouble(mutableAggBufferOffset + 1, yAvg)
+ buffer.setDouble(mutableAggBufferOffset + 2, Ck)
+ buffer.setDouble(mutableAggBufferOffset + 3, MkX)
+ buffer.setDouble(mutableAggBufferOffset + 4, MkY)
+ buffer.setLong(mutableAggBufferOffset + 5, count)
+ }
+
+ override def merge(buffer1: MutableRow, buffer2: InternalRow): Unit = {
+ val count2 = buffer2.getLong(inputAggBufferOffset + 5)
+
+ if (count2 > 0) {
+ var xAvg = buffer1.getDouble(mutableAggBufferOffset)
+ var yAvg = buffer1.getDouble(mutableAggBufferOffset + 1)
+ var Ck = buffer1.getDouble(mutableAggBufferOffset + 2)
+ var MkX = buffer1.getDouble(mutableAggBufferOffset + 3)
+ var MkY = buffer1.getDouble(mutableAggBufferOffset + 4)
+ var count = buffer1.getLong(mutableAggBufferOffset + 5)
+
+ val xAvg2 = buffer2.getDouble(inputAggBufferOffset)
+ val yAvg2 = buffer2.getDouble(inputAggBufferOffset + 1)
+ val Ck2 = buffer2.getDouble(inputAggBufferOffset + 2)
+ val MkX2 = buffer2.getDouble(inputAggBufferOffset + 3)
+ val MkY2 = buffer2.getDouble(inputAggBufferOffset + 4)
+
+ val totalCount = count + count2
+ val deltaX = xAvg - xAvg2
+ val deltaY = yAvg - yAvg2
+ Ck += Ck2 + deltaX * deltaY * count / totalCount * count2
+ xAvg = (xAvg * count + xAvg2 * count2) / totalCount
+ yAvg = (yAvg * count + yAvg2 * count2) / totalCount
+ MkX += MkX2 + deltaX * deltaX * count / totalCount * count2
+ MkY += MkY2 + deltaY * deltaY * count / totalCount * count2
+ count = totalCount
+
+ buffer1.setDouble(mutableAggBufferOffset, xAvg)
+ buffer1.setDouble(mutableAggBufferOffset + 1, yAvg)
+ buffer1.setDouble(mutableAggBufferOffset + 2, Ck)
+ buffer1.setDouble(mutableAggBufferOffset + 3, MkX)
+ buffer1.setDouble(mutableAggBufferOffset + 4, MkY)
+ buffer1.setLong(mutableAggBufferOffset + 5, count)
+ }
+ }
+
+ override def eval(buffer: InternalRow): Any = {
+ val Ck = buffer.getDouble(mutableAggBufferOffset + 2)
+ val MkX = buffer.getDouble(mutableAggBufferOffset + 3)
+ val MkY = buffer.getDouble(mutableAggBufferOffset + 4)
+ Ck / math.sqrt(MkX * MkY)
--- End diff --
From the failed test HiveCompatibilitySuite, looks like Hive will return
NULL for this case. I think we should follow it.
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