Github user hvanhovell commented on a diff in the pull request: https://github.com/apache/spark/pull/14136#discussion_r70242570 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/Percentile.scala --- @@ -0,0 +1,148 @@ +/* + * 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.InternalRow +import org.apache.spark.sql.catalyst.expressions._ +import org.apache.spark.sql.catalyst.util.GenericArrayData +import org.apache.spark.sql.types._ +import org.apache.spark.util.collection.OpenHashMap + +/** + * The Percentile aggregate function computes the exact percentile(s) of expr at pc with range in + * [0, 1]. + * The parameter pc can be a DoubleType or DoubleType array. + */ +@ExpressionDescription( + usage = """_FUNC_(epxr, pc) - Returns the percentile(s) of expr at pc (range: [0,1]). pc can be + a double or double array.""") +case class Percentile( + child: Expression, + pc: Seq[Double], + mutableAggBufferOffset: Int = 0, + inputAggBufferOffset: Int = 0) + extends ImperativeAggregate { + + def this(child: Expression, pc: Double) = { + this(child = child, pc = Seq(pc), mutableAggBufferOffset = 0, inputAggBufferOffset = 0) + } + + override def prettyName: String = "percentile" + + override def withNewMutableAggBufferOffset(newMutableAggBufferOffset: Int): ImperativeAggregate = + copy(mutableAggBufferOffset = newMutableAggBufferOffset) + + override def withNewInputAggBufferOffset(newInputAggBufferOffset: Int): ImperativeAggregate = + copy(inputAggBufferOffset = newInputAggBufferOffset) + + var counts = new OpenHashMap[Long, Long]() + + override def children: Seq[Expression] = Seq(child) + + override def nullable: Boolean = false + + override def dataType: DataType = ArrayType(DoubleType) + + override def inputTypes: Seq[AbstractDataType] = Seq(AnyDataType) + + override def supportsPartial: Boolean = false + + override def aggBufferSchema: StructType = StructType.fromAttributes(aggBufferAttributes) + + override val aggBufferAttributes: Seq[AttributeReference] = pc.map(percentile => + AttributeReference(percentile.toString, DoubleType)()) + + override val inputAggBufferAttributes: Seq[AttributeReference] = + aggBufferAttributes.map(_.newInstance()) + + override def initialize(buffer: MutableRow): Unit = { + for (i <- 0 until pc.size) { + buffer.setNullAt(mutableAggBufferOffset + i) + } + } + + override def update(buffer: MutableRow, input: InternalRow): Unit = { + val v = child.eval(input) + + v match { + case o: Int => counts.changeValue(o.toLong, 1L, _ + 1L) + case o: Long => counts.changeValue(o, 1L, _ + 1L) + case _ => return false + } + } + + override def merge(buffer: MutableRow, inputBuffer: InternalRow): Unit = { + sys.error("Percentile cannot be used in partial aggregations.") + } + + override def eval(buffer: InternalRow): Any = { + if (counts.size == 0) { + return new GenericArrayData(Seq.empty) + } + + // Sort all items and generate a sequence, then accumulate the counts + val sortedCounts = counts.toSeq.sortBy(_._1) + val aggreCounts = sortedCounts.scanLeft(0L, 0L) { (k1: (Long, Long), k2: (Long, Long)) => + (k2._1, k1._2 + k2._2) + }.drop(1) + val maxPosition = aggreCounts.last._2 - 1 + + new GenericArrayData(pc.map { percentile => + if (percentile < 0.0 || percentile > 1.0) { --- End diff -- We can check this at a much earlier stage.
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