com.yahoo.sketches.hive.tuple.ArrayOfDoublesSketchToQuantilesSketchUDF 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.tuple;
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.quantiles.DoublesSketch;
import com.yahoo.sketches.quantiles.DoublesSketchBuilder;
import com.yahoo.sketches.quantiles.UpdateDoublesSketch;
import com.yahoo.sketches.tuple.ArrayOfDoublesSketch;
import com.yahoo.sketches.tuple.ArrayOfDoublesSketchIterator;
import com.yahoo.sketches.tuple.ArrayOfDoublesSketches;
@Description(
name = "ArrayOfDoublesSketchToQuantilesSketch",
value = "_FUNC_(sketch, column, k)",
extended = "Returns a quanitles DoublesSketch constructed from a given"
+ " column of double values from a given ArrayOfDoublesSketch using parameter k"
+ " that determines the accuracy and size of the quantiles sketch."
+ " The column number is optional (the default is 1)."
+ " The parameter k is optional (the default is defined in the sketch library)."
+ " The result is a serialized quantiles sketch.")
public class ArrayOfDoublesSketchToQuantilesSketchUDF extends UDF {
/**
* Convert the first column from a given ArrayOfDoublesSketch to a quantiles DoublesSketch
* using the default parameter k.
* @param serializedSketch ArrayOfDoublesSketch in as serialized binary
* @return serialized DoublesSketch
*/
public BytesWritable evaluate(final BytesWritable serializedSketch) {
return evaluate(serializedSketch, 1, 0);
}
/**
* Convert a given column from a given ArrayOfDoublesSketch to a quantiles DoublesSketch
* using the default parameter k.
* @param serializedSketch ArrayOfDoublesSketch in as serialized binary
* @param column 1-based column number
* @return serialized DoublesSketch
*/
public BytesWritable evaluate(final BytesWritable serializedSketch, final int column) {
return evaluate(serializedSketch, column, 0);
}
/**
* Convert a given column from a given ArrayOfDoublesSketch to a quantiles DoublesSketch
* @param serializedSketch ArrayOfDoublesSketch in as serialized binary
* @param column 1-based column number
* @param k parameter that determines the accuracy and size of the quantiles sketch
* @return serialized DoublesSketch
*/
public BytesWritable evaluate(final BytesWritable serializedSketch, final int column,
final int k) {
if (serializedSketch == null) { return null; }
final ArrayOfDoublesSketch sketch = ArrayOfDoublesSketches.wrapSketch(
Memory.wrap(serializedSketch.getBytes()));
if (column < 1) {
throw new IllegalArgumentException("Column number must be greater than zero. Received: "
+ column);
}
if (column > sketch.getNumValues()) {
throw new IllegalArgumentException("Column number " + column
+ " is out of range. The given sketch has "
+ sketch.getNumValues() + " columns");
}
final DoublesSketchBuilder builder = DoublesSketch.builder();
if (k > 0) {
builder.setK(k);
}
final UpdateDoublesSketch qs = builder.build();
final ArrayOfDoublesSketchIterator it = sketch.iterator();
while (it.next()) {
qs.update(it.getValues()[column - 1]);
}
return new BytesWritable(qs.compact().toByteArray());
}
}