com.yahoo.sketches.hive.kll.GetQuantileUDF Maven / Gradle / Ivy
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/*
* Copyright 2018, Oath Inc.
* Licensed under the terms of the Apache License 2.0. See LICENSE file at the project root for terms.
*/
package com.yahoo.sketches.hive.kll;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.BytesWritable;
import com.yahoo.memory.Memory;
import com.yahoo.sketches.kll.KllFloatsSketch;
@Description(name = "GetQuantile", value = "_FUNC_(sketch, fraction)",
extended = " Returns a quantile value from a given KllFloatsSketch."
+ " A single value for a given fraction is returned."
+ " The fraction represents a normalized rank, and must be from 0 to 1 inclusive."
+ " For example, a fraction of 0.5 corresponds to 50th percentile, which is"
+ " the median value of the distribution (the number separating the higher half"
+ " of the probability distribution from the lower half).")
public class GetQuantileUDF extends UDF {
/**
* Returns a quantile value from a given sketch
* @param serializedSketch serialized sketch
* @param fraction value from 0 to 1 inclusive
* @return quantile value
*/
public Float evaluate(final BytesWritable serializedSketch, final double fraction) {
if (serializedSketch == null) { return null; }
final KllFloatsSketch sketch = KllFloatsSketch.heapify(Memory.wrap(serializedSketch.getBytes()));
return sketch.getQuantile(fraction);
}
}