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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