org.apache.mahout.text.LuceneSegmentRecordReader.java Source code

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Here is the source code for org.apache.mahout.text.LuceneSegmentRecordReader.java

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package org.apache.mahout.text;
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.lucene.index.SegmentCommitInfo;
import org.apache.lucene.index.SegmentReader;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.search.Weight;
import org.apache.lucene.store.IOContext;

import java.io.IOException;

/**
 * {@link RecordReader} implementation for Lucene segments. Each {@link InputSplit} contains a separate Lucene segment.
 * Emits records consisting of a {@link Text} document ID and a null key.
 */
public class LuceneSegmentRecordReader extends RecordReader<Text, NullWritable> {

    public static final int USE_TERM_INFO = 1;

    private SegmentReader segmentReader;
    private Scorer scorer;

    private int nextDocId;
    private Text key = new Text();

    @Override
    public void initialize(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {
        LuceneSegmentInputSplit inputSplit = (LuceneSegmentInputSplit) split;

        Configuration configuration = context.getConfiguration();
        LuceneStorageConfiguration lucene2SeqConfiguration = new LuceneStorageConfiguration(configuration);

        SegmentCommitInfo segmentInfo = inputSplit.getSegment(configuration);
        segmentReader = new SegmentReader(segmentInfo, USE_TERM_INFO, IOContext.READ);

        IndexSearcher searcher = new IndexSearcher(segmentReader);
        String idField = lucene2SeqConfiguration.getIdField();
        LuceneIndexHelper.fieldShouldExistInIndex(segmentReader, idField);
        for (String field : lucene2SeqConfiguration.getFields()) {
            LuceneIndexHelper.fieldShouldExistInIndex(segmentReader, field);
        }

        Weight weight = lucene2SeqConfiguration.getQuery().createWeight(searcher);
        scorer = weight.scorer(segmentReader.getContext(), false, false, null);
        if (scorer == null) {
            throw new IllegalArgumentException(
                    "Could not create query scorer for query: " + lucene2SeqConfiguration.getQuery());
        }
    }

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        nextDocId = scorer.nextDoc();

        return nextDocId != Scorer.NO_MORE_DOCS;
    }

    @Override
    public Text getCurrentKey() throws IOException, InterruptedException {
        key.set(String.valueOf(nextDocId));
        return key;
    }

    @Override
    public NullWritable getCurrentValue() throws IOException, InterruptedException {
        return NullWritable.get();
    }

    @Override
    public float getProgress() throws IOException, InterruptedException {
        //this is a rough estimate, due to the possible inaccuracies of cost
        return scorer.cost() == 0 ? 0 : (float) nextDocId / scorer.cost();
    }

    @Override
    public void close() throws IOException {
        segmentReader.close();
        //searcher.close();
    }
}