ivory.core.data.document.TermDocVectorsForwardIndex.java Source code

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Here is the source code for ivory.core.data.document.TermDocVectorsForwardIndex.java

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/*
 * Ivory: A Hadoop toolkit for web-scale information retrieval
 *
 * Licensed 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.
 */

package ivory.core.data.document;

import ivory.core.RetrievalEnvironment;
import ivory.core.preprocess.BuildTermDocVectorsForwardIndex;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.text.DecimalFormat;
import java.text.NumberFormat;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.log4j.Logger;

import com.google.common.base.Preconditions;

import edu.umd.cloud9.debug.MemoryUsageUtils;

/**
 * Object providing an index into one or more {@code SequenceFile}s
 * containing {@link TermDocVector}s, providing random access to the document
 * vectors.
 * 
 * @see BuildTermDocVectorsForwardIndex
 * 
 * @author Jimmy Lin
 */
public class TermDocVectorsForwardIndex {
    private static final Logger LOG = Logger.getLogger(TermDocVectorsForwardIndex.class);
    private static final NumberFormat FORMAT = new DecimalFormat("00000");

    // This is 10^15 (i.e., an exabyte). We're assuming that each individual file is smaller than
    // this value, which seems safe, at least for a while... :)
    public static final long BigNumber = 1000000000000000L;

    private final FileSystem fs;
    private final Configuration conf;
    private final long[] positions;
    private final String path;
    private final int docnoOffset;
    private final int collectionDocumentCount;

    /**
     * Creates a {code TermDocVectorsIndex} object.
     *
     * @param indexPath location of the index file
     * @param fs handle to the FileSystem
     * @throws IOException
     */
    public TermDocVectorsForwardIndex(String indexPath, FileSystem fs) throws IOException {
        Preconditions.checkNotNull(indexPath);
        this.fs = Preconditions.checkNotNull(fs);
        conf = fs.getConf();

        RetrievalEnvironment env = new RetrievalEnvironment(indexPath, fs);
        path = env.getTermDocVectorsDirectory();

        FSDataInputStream posInput = fs.open(new Path(env.getTermDocVectorsForwardIndex()));

        docnoOffset = posInput.readInt();
        collectionDocumentCount = posInput.readInt();

        positions = new long[collectionDocumentCount];
        for (int i = 0; i < collectionDocumentCount; i++) {
            positions[i] = posInput.readLong();
        }
        posInput.close();
    }

    /**
     * Returns the document vector given a docno.
     */
    public TermDocVector getDocVector(int docno) throws IOException {
        // TODO: This method re-opens the SequenceFile on every access.
        // Would be more efficient to cache the file handles.
        if (docno > collectionDocumentCount || docno < 1) {
            return null;
        }

        long pos = positions[docno - docnoOffset - 1];

        int fileNo = (int) (pos / BigNumber);
        pos = pos % BigNumber;

        SequenceFile.Reader reader = null;
        try {
            reader = new SequenceFile.Reader(fs, new Path(path + "/part-m-" + FORMAT.format(fileNo)), conf);
        } catch (IOException e) {
            // Try alternative naming scheme for output of old API.
            reader = new SequenceFile.Reader(fs, new Path(path + "/part-" + FORMAT.format(fileNo)), conf);
        }

        IntWritable key = new IntWritable();
        TermDocVector value;

        try {
            value = (TermDocVector) reader.getValueClass().newInstance();
        } catch (Exception e) {
            throw new RuntimeException("Unable to instantiate key/value pair!");
        }

        reader.seek(pos);
        reader.next(key, value);

        if (key.get() != docno) {
            LOG.error(String.format("Unable to doc vector for docno %d: found docno %d instead.", docno, key));
            return null;
        }

        reader.close();
        return value;
    }

    /**
     * Simple test program.
     */
    public static void main(String[] args) throws Exception {
        if (args.length != 1) {
            System.out.println("usage: [indexPath]");
            System.exit(-1);
        }

        long startingMemoryUse = MemoryUsageUtils.getUsedMemory();
        Configuration conf = new Configuration();
        TermDocVectorsForwardIndex index = new TermDocVectorsForwardIndex(args[0], FileSystem.get(conf));
        long endingMemoryUse = MemoryUsageUtils.getUsedMemory();

        System.out.println("Memory usage: " + (endingMemoryUse - startingMemoryUse) + " bytes\n");

        String term = null;
        BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Look up postings of doc > ");
        while ((term = stdin.readLine()) != null) {
            int docno = Integer.parseInt(term);
            System.out.println(docno + ": " + index.getDocVector(docno));
            System.out.print("Look up postings of doc > ");
        }
    }
}