spark MaxByAndMinBy 源码

spark MaxByAndMinBy 代码

文件路径：/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/MaxByAndMinBy.scala

/*
 * 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.TypeCheckResult
import org.apache.spark.sql.catalyst.dsl.expressions._
import org.apache.spark.sql.catalyst.expressions._
import org.apache.spark.sql.catalyst.trees.BinaryLike
import org.apache.spark.sql.catalyst.util.TypeUtils
import org.apache.spark.sql.types._

/**
 * The shared abstract superclass for `MaxBy` and `MinBy` SQL aggregate functions.
 */
abstract class MaxMinBy extends DeclarativeAggregate with BinaryLike[Expression] {

  def valueExpr: Expression
  def orderingExpr: Expression

  // The predicate compares two ordering values.
  protected def predicate(oldExpr: Expression, newExpr: Expression): Expression
  // The arithmetic expression returns greatest/least value of all parameters.
  // Used to pick up updated ordering value.
  protected def orderingUpdater(oldExpr: Expression, newExpr: Expression): Expression

  override def left: Expression = valueExpr
  override def right: Expression = orderingExpr

  override def nullable: Boolean = true

  // Return data type.
  override def dataType: DataType = valueExpr.dataType

  override def checkInputDataTypes(): TypeCheckResult =
    TypeUtils.checkForOrderingExpr(orderingExpr.dataType, s"function $prettyName")

  // The attributes used to keep extremum (max or min) and associated aggregated values.
  private lazy val extremumOrdering =
    AttributeReference("extremumOrdering", orderingExpr.dataType)()
  private lazy val valueWithExtremumOrdering =
    AttributeReference("valueWithExtremumOrdering", valueExpr.dataType)()

  override lazy val aggBufferAttributes: Seq[AttributeReference] =
    valueWithExtremumOrdering :: extremumOrdering :: Nil

  private lazy val nullValue = Literal.create(null, valueExpr.dataType)
  private lazy val nullOrdering = Literal.create(null, orderingExpr.dataType)

  override lazy val initialValues: Seq[Literal] = Seq(
    /* valueWithExtremumOrdering = */ nullValue,
    /* extremumOrdering = */ nullOrdering
  )

  override lazy val updateExpressions: Seq[Expression] = Seq(
    /* valueWithExtremumOrdering = */
    CaseWhen(
      (extremumOrdering.isNull && orderingExpr.isNull, nullValue) ::
        (extremumOrdering.isNull, valueExpr) ::
        (orderingExpr.isNull, valueWithExtremumOrdering) :: Nil,
      If(predicate(extremumOrdering, orderingExpr), valueWithExtremumOrdering, valueExpr)
    ),
    /* extremumOrdering = */ orderingUpdater(extremumOrdering, orderingExpr)
  )

  override lazy val mergeExpressions: Seq[Expression] = Seq(
    /* valueWithExtremumOrdering = */
    CaseWhen(
      (extremumOrdering.left.isNull && extremumOrdering.right.isNull, nullValue) ::
        (extremumOrdering.left.isNull, valueWithExtremumOrdering.right) ::
        (extremumOrdering.right.isNull, valueWithExtremumOrdering.left) :: Nil,
      If(predicate(extremumOrdering.left, extremumOrdering.right),
        valueWithExtremumOrdering.left, valueWithExtremumOrdering.right)
    ),
    /* extremumOrdering = */ orderingUpdater(extremumOrdering.left, extremumOrdering.right)
  )

  override lazy val evaluateExpression: AttributeReference = valueWithExtremumOrdering
}

@ExpressionDescription(
  usage = "_FUNC_(x, y) - Returns the value of `x` associated with the maximum value of `y`.",
  examples = """
    Examples:
      > SELECT _FUNC_(x, y) FROM VALUES (('a', 10)), (('b', 50)), (('c', 20)) AS tab(x, y);
       b
  """,
  group = "agg_funcs",
  since = "3.0.0")
case class MaxBy(valueExpr: Expression, orderingExpr: Expression) extends MaxMinBy {

  override def prettyName: String = "max_by"

  override protected def predicate(oldExpr: Expression, newExpr: Expression): Expression =
    oldExpr > newExpr

  override protected def orderingUpdater(oldExpr: Expression, newExpr: Expression): Expression =
    greatest(oldExpr, newExpr)

  override protected def withNewChildrenInternal(newLeft: Expression, newRight: Expression): MaxBy =
    copy(valueExpr = newLeft, orderingExpr = newRight)
}

@ExpressionDescription(
  usage = "_FUNC_(x, y) - Returns the value of `x` associated with the minimum value of `y`.",
  examples = """
    Examples:
      > SELECT _FUNC_(x, y) FROM VALUES (('a', 10)), (('b', 50)), (('c', 20)) AS tab(x, y);
       a
  """,
  group = "agg_funcs",
  since = "3.0.0")
case class MinBy(valueExpr: Expression, orderingExpr: Expression) extends MaxMinBy {

  override def prettyName: String = "min_by"

  override protected def predicate(oldExpr: Expression, newExpr: Expression): Expression =
    oldExpr < newExpr

  override protected def orderingUpdater(oldExpr: Expression, newExpr: Expression): Expression =
    least(oldExpr, newExpr)

  override protected def withNewChildrenInternal(newLeft: Expression, newRight: Expression): MinBy =
    copy(valueExpr = newLeft, orderingExpr = newRight)
}

相关信息

spark 源码目录

相关文章

spark AnyValue 源码

spark ApproxCountDistinctForIntervals 源码

spark ApproximatePercentile 源码

spark Average 源码

spark BloomFilterAggregate 源码

spark CentralMomentAgg 源码

spark Corr 源码

spark Count 源码

spark CountIf 源码

spark CountMinSketchAgg 源码