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(searcher, idField);
for (String field : lucene2SeqConfiguration.getFields()) {
LuceneIndexHelper.fieldShouldExistInIndex(searcher, 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();
}
}