org.apache.hadoop.hive.ql.udf.generic.GenericUDAFCumeDist Maven / Gradle / Ivy
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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,
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* See the License for the specific language governing permissions and
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package org.apache.hadoop.hive.ql.udf.generic;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.WindowFunctionDescription;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.serde2.io.DoubleWritable;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.io.IntWritable;
@WindowFunctionDescription
(
description = @Description(
name = "cume_dist",
value = "_FUNC_(x) - The CUME_DIST function (defined as the inverse of percentile in some " +
"statistical books) computes the position of a specified value relative to a set of values. " +
"To compute the CUME_DIST of a value x in a set S of size N, you use the formula: " +
"CUME_DIST(x) = number of values in S coming before " +
" and including x in the specified order/ N"
),
supportsWindow = false,
pivotResult = true,
rankingFunction = true,
impliesOrder = true
)
public class GenericUDAFCumeDist extends GenericUDAFRank {
static final Log LOG = LogFactory.getLog(GenericUDAFCumeDist.class.getName());
@Override
protected GenericUDAFAbstractRankEvaluator createEvaluator() {
return new GenericUDAFCumeDistEvaluator();
}
public static class GenericUDAFCumeDistEvaluator extends GenericUDAFAbstractRankEvaluator {
@Override
public ObjectInspector init(Mode m, ObjectInspector[] parameters) throws HiveException {
super.init(m, parameters);
return ObjectInspectorFactory
.getStandardListObjectInspector(PrimitiveObjectInspectorFactory.writableDoubleObjectInspector);
}
@Override
public Object terminate(AggregationBuffer agg) throws HiveException {
List ranks = ((RankBuffer) agg).rowNums;
int ranksSize = ranks.size();
double ranksSizeDouble = ranksSize;
List distances = new ArrayList(ranksSize);
int last = -1;
int current = -1;
// tracks the number of elements with the same rank at the current time
int elementsAtRank = 1;
for (int index = 0; index < ranksSize; index++) {
current = ranks.get(index).get();
if (index == 0) {
last = current;
} else if (last == current) {
elementsAtRank++;
} else {
last = current;
double distance = ((double) index) / ranksSizeDouble;
while (elementsAtRank-- > 0) {
distances.add(new DoubleWritable(distance));
}
elementsAtRank = 1;
}
}
if (ranksSize > 0 && last == current) {
double distance = ((double) ranksSize) / ranksSizeDouble;
while (elementsAtRank-- > 0) {
distances.add(new DoubleWritable(distance));
}
}
return distances;
}
}
}