com.yahoo.sketches.hive.hll.SketchToEstimateUDF Maven / Gradle / Ivy
/*
* Copyright 2017, Yahoo! 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.hll;
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.hll.HllSketch;
@Description(
name = "SketchToEstimate",
value = "_FUNC_(sketch)",
extended = "Returns an estimate of unique count from a given HllSketch."
+ " The result is a double value.")
public class SketchToEstimateUDF extends UDF {
/**
* Get an estimate from a given HllSketch
* @param serializedSketch HllSketch in a serialized binary form
* @return estimate of unique count
*/
public Double evaluate(final BytesWritable serializedSketch) {
if (serializedSketch == null) { return null; }
final HllSketch sketch = HllSketch.wrap(Memory.wrap(serializedSketch.getBytes()));
return sketch.getEstimate();
}
}