| /* |
| * Copyright 2019, Verizon Media. |
| * Licensed under the terms of the Apache License 2.0. See LICENSE file at the project root for terms. |
| */ |
| |
| package com.yahoo.sketches.pig.cpc; |
| |
| import static com.yahoo.sketches.Util.DEFAULT_UPDATE_SEED; |
| |
| import java.io.IOException; |
| |
| import org.apache.pig.EvalFunc; |
| import org.apache.pig.data.DataByteArray; |
| import org.apache.pig.data.Tuple; |
| |
| import com.yahoo.sketches.cpc.CpcSketch; |
| |
| /** |
| * This is a User Defined Function (UDF) for getting a distinct count estimate from a given CpcdSketch |
| * |
| * @author Alexander Saydakov |
| */ |
| public class GetEstimate extends EvalFunc<Double> { |
| |
| private final long seed_; |
| |
| /** |
| * Constructor with default seed |
| */ |
| public GetEstimate() { |
| this(DEFAULT_UPDATE_SEED); |
| } |
| |
| /** |
| * Constructor with given seed |
| * @param seed in a form of a String |
| */ |
| public GetEstimate(final String seed) { |
| this(Long.parseLong(seed)); |
| } |
| |
| /** |
| * Base constructor |
| * @param seed parameter for the hash function |
| */ |
| GetEstimate(final long seed) { |
| seed_ = seed; |
| } |
| |
| @Override |
| public Double exec(final Tuple sketchTuple) throws IOException { |
| if ((sketchTuple == null) || (sketchTuple.size() == 0)) { |
| return null; |
| } |
| final DataByteArray dba = (DataByteArray) sketchTuple.get(0); |
| final CpcSketch sketch = CpcSketch.heapify(dba.get(), seed_); |
| return sketch.getEstimate(); |
| } |
| |
| } |