ivory.core.data.index.IntPostingsForwardIndex.java Source code

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Here is the source code for ivory.core.data.index.IntPostingsForwardIndex.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.index;

import ivory.core.RetrievalEnvironment;

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 edu.umd.cloud9.debug.MemoryUsageUtils;

public class IntPostingsForwardIndex {
    private static final Logger LOG = Logger.getLogger(IntPostingsForwardIndex.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 long[] positions;
    private final String postingsPath;
    private final FileSystem fs;
    private final Configuration conf;

    public IntPostingsForwardIndex(String indexPath, FileSystem fs) throws IOException {
        this.fs = fs;
        this.conf = fs.getConf();
        RetrievalEnvironment env = new RetrievalEnvironment(indexPath, fs);
        postingsPath = env.getPostingsDirectory();

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

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

    public PostingsList getPostingsList(int termid) throws IOException {
        // TODO: This method re-opens the SequenceFile on every access. Would be more efficient to cache
        // the file handles.

        long pos = positions[termid - 1];

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

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

        IntWritable key = new IntWritable();
        PostingsList value = null;
        try {
            value = (PostingsList) Class.forName(reader.getValueClassName()).newInstance();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }

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

        if (key.get() != termid) {
            LOG.error("unable to fetch postings for term \"" + termid + "\": found key \"" + key + "\" instead");
            return null;
        }

        reader.close();
        return value;
    }

    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();
        IntPostingsForwardIndex index = new IntPostingsForwardIndex(args[0], FileSystem.getLocal(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 termid > ");
        while ((term = stdin.readLine()) != null) {
            int termid = Integer.parseInt(term);
            System.out.println(termid + ": " + index.getPostingsList(termid));
            System.out.print("Look up postings of termid > ");
        }
    }
}