| /* |
| * 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.pig.quantiles; |
| |
| import java.io.IOException; |
| import java.util.Comparator; |
| |
| import org.apache.pig.EvalFunc; |
| import org.apache.pig.data.DataByteArray; |
| import org.apache.pig.data.Tuple; |
| |
| import com.yahoo.memory.Memory; |
| import com.yahoo.sketches.ArrayOfStringsSerDe; |
| import com.yahoo.sketches.quantiles.ItemsSketch; |
| |
| /** |
| * This UDF is to get an approximation to the Probability Mass Function (PMF) of the input stream |
| * given a sketch and a set of split points - an array of <i>m</i> unique, monotonically increasing |
| * values that divide the domain into <i>m+1</i> consecutive disjoint intervals. |
| * The function returns an array of m+1 doubles each of which is an approximation to the fraction |
| * of the input stream values that fell into one of those intervals. Intervals are inclusive of |
| * the left split point and exclusive of the right split point. |
| */ |
| public class GetPmfFromStringsSketch extends EvalFunc<Tuple> { |
| |
| @Override |
| public Tuple exec(final Tuple input) throws IOException { |
| if (input.size() < 2) { |
| throw new IllegalArgumentException("expected two or more inputs: sketch and list of split points"); |
| } |
| |
| if (!(input.get(0) instanceof DataByteArray)) { |
| throw new IllegalArgumentException( |
| "expected a DataByteArray as a sketch, got " + input.get(0).getClass().getSimpleName()); |
| } |
| final DataByteArray dba = (DataByteArray) input.get(0); |
| final ItemsSketch<String> sketch = |
| ItemsSketch.getInstance(Memory.wrap(dba.get()), Comparator.naturalOrder(), |
| new ArrayOfStringsSerDe()); |
| |
| final String[] splitPoints = new String[input.size() - 1]; |
| for (int i = 1; i < input.size(); i++) { |
| if (!(input.get(i) instanceof String)) { |
| throw new IllegalArgumentException("expected a string value as a split point, got " |
| + input.get(i).getClass().getSimpleName()); |
| } |
| splitPoints[i - 1] = (String) input.get(i); |
| } |
| final double[] pmf = sketch.getPMF(splitPoints); |
| if (pmf == null) { return null; } |
| return Util.doubleArrayToTuple(pmf); |
| } |
| |
| } |