package edu.umd.cloud9.collection.wikipedia;
import java.io.IOException;
import java.text.DecimalFormat;
import java.util.Arrays;
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.collection.DocumentForwardIndex;
import edu.umd.cloud9.collection.wikipedia.language.WikipediaPageFactory;
/**
* Forward index for Wikipedia collections.
*
* @author Jimmy Lin
* @author Peter Exner
*/
public class WikipediaForwardIndex implements DocumentForwardIndex<WikipediaPage> {
private static final Logger LOG = Logger.getLogger(WikipediaPage.class);
private Configuration conf;
private int[] docnos;
private int[] offsets;
private short[] fileno;
private String collectionPath;
private int lastDocno = -1;
private WikipediaDocnoMapping docnoMapping = new WikipediaDocnoMapping();
public WikipediaForwardIndex() {
conf = new Configuration();
}
public WikipediaForwardIndex(Configuration conf) {
this.conf = Preconditions.checkNotNull(conf);
}
@Override
public void loadIndex(Path index, Path mapping, FileSystem fs) throws IOException {
LOG.info("Loading forward index: " + index);
docnoMapping.loadMapping(mapping, fs);
FSDataInputStream in = fs.open(index);
// Class name; throw away.
in.readUTF();
collectionPath = in.readUTF();
int blocks = in.readInt();
LOG.info(blocks + " blocks expected");
docnos = new int[blocks];
offsets = new int[blocks];
fileno = new short[blocks];
for (int i = 0; i < blocks; i++) {
docnos[i] = in.readInt();
offsets[i] = in.readInt();
fileno[i] = in.readShort();
if (i > 0 && i % 100000 == 0)
LOG.info(i + " blocks read");
}
in.close();
}
@Override
public String getCollectionPath() {
return collectionPath;
}
@Override
public WikipediaPage getDocument(int docno) {
long start = System.currentTimeMillis();
// trap invalid docnos
if (docno < getFirstDocno() || docno > getLastDocno())
return null;
int idx = Arrays.binarySearch(docnos, docno);
if (idx < 0) {
idx = -idx - 2;
}
try {
FileSystem fs = FileSystem.get(conf);
DecimalFormat df = new DecimalFormat("00000");
Path file = new Path(collectionPath + "/part-m-" + df.format(fileno[idx]));
// Try the old file naming convention.
if (!fs.exists(file)) {
file = new Path(collectionPath + "/part-" + df.format(fileno[idx]));
}
LOG.info("fetching docno " + docno + ": seeking to " + offsets[idx] + " at " + file);
SequenceFile.Reader reader = new SequenceFile.Reader(conf,
SequenceFile.Reader.file(file));
IntWritable key = new IntWritable();
WikipediaPage value = WikipediaPageFactory.createWikipediaPage(conf.get("wiki.language"));
reader.seek(offsets[idx]);
while (reader.next(key)) {
if (key.get() == docno)
break;
}
reader.getCurrentValue(value);
reader.close();
long duration = System.currentTimeMillis() - start;
LOG.info(" docno " + docno + " fetched in " + duration + "ms");
return value;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
public WikipediaPage getDocument(String docid) {
return getDocument(docnoMapping.getDocno(docid));
}
@Override
public int getDocno(String docid) {
return docnoMapping.getDocno(docid);
}
@Override
public String getDocid(int docno) {
return docnoMapping.getDocid(docno);
}
@Override
public int getFirstDocno() {
return docnos[0];
}
@Override
public int getLastDocno() {
if (lastDocno != -1) {
return lastDocno;
}
// find the last entry, and then see all the way to the end of the
// collection
int idx = docnos.length - 1;
try {
FileSystem fs = FileSystem.get(conf);
DecimalFormat df = new DecimalFormat("00000");
Path file = new Path(collectionPath + "/part-m-" + df.format(fileno[idx]));
// Try the old file naming convention.
if (!fs.exists(file)) {
file = new Path(collectionPath + "/part-" + df.format(fileno[idx]));
}
SequenceFile.Reader reader = new SequenceFile.Reader(conf,
SequenceFile.Reader.file(file));
IntWritable key = new IntWritable();
reader.seek(offsets[idx]);
while (reader.next(key));
lastDocno = key.get();
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
return lastDocno;
}
}