| /* |
| * Copyright 2016, 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.quantiles; |
| |
| import java.util.Arrays; |
| import java.util.Comparator; |
| import java.util.List; |
| |
| 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.ArrayOfStringsSerDe; |
| import com.yahoo.sketches.quantiles.ItemsSketch; |
| |
| @Description( |
| name = "GetQuantiles", |
| value = "_FUNC_(sketch, fractions...) or _FUNC_(sketch, number)", |
| extended = "Returns quantile values from a given ItemsSketch<String> based on a given" |
| + " list of fractions or a number of evenly spaced fractions." |
| + " The fractions represent normalized ranks, 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)." |
| + " The number of evenly spaced fractions must be a positive integer greater than 0." |
| + " A value of 1 will return the min value (normalized rank of 0.0)." |
| + " A value of 2 will return the min and the max value (ranks 0.0 amd 1.0)." |
| + " A value of 3 will return the min, the median and the max value (ranks 0.0, 0.5, and 1.0), etc.") |
| public class GetQuantilesFromStringsSketchUDF extends UDF { |
| |
| /** |
| * Returns a list of quantile values from a given sketch |
| * @param serializedSketch serialized sketch |
| * @param fractions list of values from 0 to 1 inclusive |
| * @return list of quantile values |
| */ |
| public List<String> evaluate(final BytesWritable serializedSketch, final Double... fractions) { |
| if (serializedSketch == null) { return null; } |
| final ItemsSketch<String> sketch = ItemsSketch.getInstance( |
| Memory.wrap(serializedSketch.getBytes()), |
| Comparator.naturalOrder(), |
| new ArrayOfStringsSerDe() |
| ); |
| return Arrays.asList(sketch.getQuantiles(Util.objectsToPrimitives(fractions))); |
| } |
| |
| /** |
| * Returns a list of quantile values from a given sketch |
| * @param serializedSketch serialized sketch |
| * @param number of evenly spaced fractions |
| * @return list of quantile values |
| */ |
| public List<String> evaluate(final BytesWritable serializedSketch, final int number) { |
| if (serializedSketch == null) { return null; } |
| final ItemsSketch<String> sketch = ItemsSketch.getInstance( |
| Memory.wrap(serializedSketch.getBytes()), |
| Comparator.naturalOrder(), |
| new ArrayOfStringsSerDe() |
| ); |
| final String[] quantiles = sketch.getQuantiles(number); |
| if (quantiles == null) { return null; } |
| return Arrays.asList(quantiles); |
| } |
| |
| } |