org.apache.spark.sql.catalyst.expressions.aggregate.Average.scala Maven / Gradle / Ivy
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*
* http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.spark.sql.catalyst.expressions.aggregate
import org.apache.spark.sql.catalyst.analysis.{DecimalPrecision, TypeCheckResult}
import org.apache.spark.sql.catalyst.dsl.expressions._
import org.apache.spark.sql.catalyst.expressions._
import org.apache.spark.sql.catalyst.util.TypeUtils
import org.apache.spark.sql.types._
abstract class AverageLike(child: Expression) extends DeclarativeAggregate {
override def nullable: Boolean = true
// Return data type.
override def dataType: DataType = resultType
private lazy val resultType = child.dataType match {
case DecimalType.Fixed(p, s) =>
DecimalType.bounded(p + 4, s + 4)
case _ => DoubleType
}
private lazy val sumDataType = child.dataType match {
case _ @ DecimalType.Fixed(p, s) => DecimalType.bounded(p + 10, s)
case _ => DoubleType
}
private lazy val sum = AttributeReference("sum", sumDataType)()
private lazy val count = AttributeReference("count", LongType)()
override lazy val aggBufferAttributes = sum :: count :: Nil
override lazy val initialValues = Seq(
/* sum = */ Literal(0).cast(sumDataType),
/* count = */ Literal(0L)
)
override lazy val mergeExpressions = Seq(
/* sum = */ sum.left + sum.right,
/* count = */ count.left + count.right
)
// If all input are nulls, count will be 0 and we will get null after the division.
override lazy val evaluateExpression = child.dataType match {
case _: DecimalType =>
DecimalPrecision.decimalAndDecimal(sum / count.cast(DecimalType.LongDecimal)).cast(resultType)
case _ =>
sum.cast(resultType) / count.cast(resultType)
}
protected def updateExpressionsDef: Seq[Expression] = Seq(
/* sum = */
Add(
sum,
coalesce(child.cast(sumDataType), Literal(0).cast(sumDataType))),
/* count = */ If(child.isNull, count, count + 1L)
)
override lazy val updateExpressions = updateExpressionsDef
}
@ExpressionDescription(
usage = "_FUNC_(expr) - Returns the mean calculated from values of a group.")
case class Average(child: Expression)
extends AverageLike(child) with ImplicitCastInputTypes {
override def prettyName: String = "avg"
override def children: Seq[Expression] = child :: Nil
override def inputTypes: Seq[AbstractDataType] = Seq(NumericType)
override def checkInputDataTypes(): TypeCheckResult =
TypeUtils.checkForNumericExpr(child.dataType, "function average")
}