/
Average.scala
96 lines (80 loc) · 3.56 KB
/
Average.scala
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.spark.sql.catalyst.expressions.aggregate
import org.apache.spark.sql.catalyst.analysis.{DecimalPrecision, FunctionRegistry}
import org.apache.spark.sql.catalyst.dsl.expressions._
import org.apache.spark.sql.catalyst.expressions._
import org.apache.spark.sql.types._
@ExpressionDescription(
usage = "_FUNC_(expr) - Returns the mean calculated from values of a group.",
examples = """
Examples:
> SELECT _FUNC_(col) FROM VALUES (1), (2), (3) AS tab(col);
2.0
> SELECT _FUNC_(col) FROM VALUES (1), (2), (NULL) AS tab(col);
1.5
> SELECT _FUNC_(cast(v as interval)) FROM VALUES ('-1 weeks'), ('2 seconds'), (null) t(v);
-3 days -11 hours -59 minutes -59 seconds
""",
since = "1.0.0")
case class Average(child: Expression) extends DeclarativeAggregate with ImplicitCastInputTypes {
override def prettyName: String = getTagValue(FunctionRegistry.FUNC_ALIAS).getOrElse("avg")
override def children: Seq[Expression] = child :: Nil
override def inputTypes: Seq[AbstractDataType] = Seq(TypeCollection.NumericAndInterval)
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 interval: CalendarIntervalType => interval
case _ => DoubleType
}
private lazy val sumDataType = child.dataType match {
case _ @ DecimalType.Fixed(p, s) => DecimalType.bounded(p + 10, s)
case interval: CalendarIntervalType => interval
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.default(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 CalendarIntervalType =>
val newCount = If(EqualTo(count, Literal(0L)), Literal(null, LongType), count)
DivideInterval(sum.cast(resultType), newCount.cast(DoubleType))
case _ =>
sum.cast(resultType) / count.cast(resultType)
}
override lazy val updateExpressions: Seq[Expression] = Seq(
/* sum = */
Add(
sum,
coalesce(child.cast(sumDataType), Literal.default(sumDataType))),
/* count = */ If(child.isNull, count, count + 1L)
)
}