import java.io.IOException;
import java.io.File;
import java.io.PrintStream;
import java.util.Vector;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.RAMDirectory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.store.Lock;
import org.apache.lucene.store.InputStream;
import org.apache.lucene.store.OutputStream;
import org.apache.lucene.document.Document;
import org.apache.lucene.analysis.Analyzer;
public final class IndexWriter {
private Directory directory; // where this index resides
private Analyzer analyzer; // how to analyze text
private SegmentInfos segmentInfos = new SegmentInfos(); // the segments
private final Directory ramDirectory = new RAMDirectory(); // for temp segs
/** Constructs an IndexWriter for the index in <code>path</code>. Text will
be analyzed with <code>a</code>. If <code>create</code> is true, then a
new, empty index will be created in <code>d</code>, replacing the index
already there, if any. */
public IndexWriter(String path, Analyzer a, boolean create)
throws IOException {
this(FSDirectory.getDirectory(path, create), a, create);
}
/** Constructs an IndexWriter for the index in <code>path</code>. Text will
be analyzed with <code>a</code>. If <code>create</code> is true, then a
new, empty index will be created in <code>d</code>, replacing the index
already there, if any. */
public IndexWriter(File path, Analyzer a, boolean create)
throws IOException {
this(FSDirectory.getDirectory(path, create), a, create);
}
/** Constructs an IndexWriter for the index in <code>d</code>. Text will be
analyzed with <code>a</code>. If <code>create</code> is true, then a new,
empty index will be created in <code>d</code>, replacing the index already
there, if any. */
public IndexWriter(Directory d, Analyzer a, final boolean create)
throws IOException {
directory = d;
analyzer = a;
Lock writeLock = directory.makeLock("write.lock");
if (!writeLock.obtain()) // obtain write lock
throw new IOException("Index locked for write: " + writeLock);
synchronized (directory) { // in- & inter-process sync
new Lock.With(directory.makeLock("commit.lock")) {
public Object doBody() throws IOException {
if (create)
segmentInfos.write(directory);
else
segmentInfos.read(directory);
return null;
}
}.run();
}
}
/** Flushes all changes to an index, closes all associated files, and closes
the directory that the index is stored in. */
public final synchronized void close() throws IOException {
flushRamSegments();
ramDirectory.close();
directory.makeLock("write.lock").release(); // release write lock
directory.close();
}
/** Returns the number of documents currently in this index. */
public final synchronized int docCount() {
int count = 0;
for (int i = 0; i < segmentInfos.size(); i++) {
SegmentInfo si = segmentInfos.info(i);
count += si.docCount;
}
return count;
}
/** The maximum number of terms that will be indexed for a single field in a
document. This limits the amount of memory required for indexing, so that
collections with very large files will not crash the indexing process by
running out of memory.
<p>By default, no more than 10,000 terms will be indexed for a field. */
public int maxFieldLength = 10000;
/** Adds a document to this index.*/
public final void addDocument(Document doc) throws IOException {
DocumentWriter dw =
new DocumentWriter(ramDirectory, analyzer, maxFieldLength);
String segmentName = newSegmentName();
dw.addDocument(segmentName, doc);
synchronized (this) {
segmentInfos.addElement(new SegmentInfo(segmentName, 1, ramDirectory));
maybeMergeSegments();
}
}
private final synchronized String newSegmentName() {
return "_" + Integer.toString(segmentInfos.counter++, Character.MAX_RADIX);
}
/** Determines how often segment indexes are merged by addDocument(). With
* smaller values, less RAM is used while indexing, and searches on
* unoptimized indexes are faster, but indexing speed is slower. With larger
* values more RAM is used while indexing and searches on unoptimized indexes
* are slower, but indexing is faster. Thus larger values (> 10) are best
* for batched index creation, and smaller values (< 10) for indexes that are
* interactively maintained.
*
* <p>This must never be less than 2. The default value is 10.*/
public int mergeFactor = 10;
/** Determines the largest number of documents ever merged by addDocument().
* Small values (e.g., less than 10,000) are best for interactive indexing,
* as this limits the length of pauses while indexing to a few seconds.
* Larger values are best for batched indexing and speedier searches.
*
* <p>The default value is {@link Integer#MAX_VALUE}. */
public int maxMergeDocs = Integer.MAX_VALUE;
/** If non-null, information about merges will be printed to this. */
public PrintStream infoStream = null;
/** Merges all segments together into a single segment, optimizing an index
for search. */
public final synchronized void optimize() throws IOException {
flushRamSegments();
while (segmentInfos.size() > 1 ||
(segmentInfos.size() == 1 &&
SegmentReader.hasDeletions(segmentInfos.info(0)))){
int minSegment = segmentInfos.size() - mergeFactor;
mergeSegments(minSegment < 0 ? 0 : minSegment);
}
}
/** Merges all segments from an array of indexes into this index.
*
* <p>This may be used to parallelize batch indexing. A large document
* collection can be broken into sub-collections. Each sub-collection can be
* indexed in parallel, on a different thread, process or machine. The
* complete index can then be created by merging sub-collection indexes
* with this method.
*
* <p>After this completes, the index is optimized. */
public final synchronized void addIndexes(Directory[] dirs)
throws IOException {
optimize(); // start with zero or 1 seg
int minSegment = segmentInfos.size();
int segmentsAddedSinceMerge = 0;
for (int i = 0; i < dirs.length; i++) {
SegmentInfos sis = new SegmentInfos(); // read infos from dir
sis.read(dirs[i]);
for (int j = 0; j < sis.size(); j++) {
segmentInfos.addElement(sis.info(j)); // add each info
// merge whenever mergeFactor segments have been added
if (++segmentsAddedSinceMerge == mergeFactor) {
mergeSegments(minSegment++, false);
segmentsAddedSinceMerge = 0;
}
}
}
optimize(); // final cleanup
}
/** Merges all RAM-resident segments. */
private final void flushRamSegments() throws IOException {
int minSegment = segmentInfos.size()-1;
int docCount = 0;
while (minSegment >= 0 &&
(segmentInfos.info(minSegment)).dir == ramDirectory) {
docCount += segmentInfos.info(minSegment).docCount;
minSegment--;
}
if (minSegment < 0 || // add one FS segment?
(docCount + segmentInfos.info(minSegment).docCount) > mergeFactor ||
!(segmentInfos.info(segmentInfos.size()-1).dir == ramDirectory))
minSegment++;
if (minSegment >= segmentInfos.size())
return; // none to merge
mergeSegments(minSegment);
}
/** Incremental segment merger. */
private final void maybeMergeSegments() throws IOException {
long targetMergeDocs = mergeFactor;
while (targetMergeDocs <= maxMergeDocs) {
// find segments smaller than current target size
int minSegment = segmentInfos.size();
int mergeDocs = 0;
while (--minSegment >= 0) {
SegmentInfo si = segmentInfos.info(minSegment);
if (si.docCount >= targetMergeDocs)
break;
mergeDocs += si.docCount;
}
if (mergeDocs >= targetMergeDocs) // found a merge to do
mergeSegments(minSegment+1);
else
break;
targetMergeDocs *= mergeFactor; // increase target size
}
}
/** Pops segments off of segmentInfos stack down to minSegment, merges them,
and pushes the merged index onto the top of the segmentInfos stack. */
private final void mergeSegments(int minSegment) throws IOException {
mergeSegments(minSegment, true);
}
/** Pops segments off of segmentInfos stack down to minSegment, merges them,
and pushes the merged index onto the top of the segmentInfos stack. */
private final void mergeSegments(int minSegment, boolean delete)
throws IOException {
String mergedName = newSegmentName();
int mergedDocCount = 0;
if (infoStream != null) infoStream.print("merging segments");
SegmentMerger merger = new SegmentMerger(directory, mergedName);
final Vector segmentsToDelete = new Vector();
for (int i = minSegment; i < segmentInfos.size(); i++) {
SegmentInfo si = segmentInfos.info(i);
if (infoStream != null)
infoStream.print(" " + si.name + " (" + si.docCount + " docs)");
SegmentReader reader = new SegmentReader(si);
merger.add(reader);
if (delete)
segmentsToDelete.addElement(reader); // queue for deletion
mergedDocCount += si.docCount;
}
if (infoStream != null) {
infoStream.println();
infoStream.println(" into "+mergedName+" ("+mergedDocCount+" docs)");
}
merger.merge();
segmentInfos.setSize(minSegment); // pop old infos & add new
segmentInfos.addElement(new SegmentInfo(mergedName, mergedDocCount,
directory));
synchronized (directory) { // in- & inter-process sync
new Lock.With(directory.makeLock("commit.lock")) {
public Object doBody() throws IOException {
segmentInfos.write(directory); // commit before deleting
deleteSegments(segmentsToDelete); // delete now-unused segments
return null;
}
}.run();
}
}
/* Some operating systems (e.g. Windows) don't permit a file to be deleted
while it is opened for read (e.g. by another process or thread). So we
assume that when a delete fails it is because the file is open in another
process, and queue the file for subsequent deletion. */
private final void deleteSegments(Vector segments) throws IOException {
Vector deletable = new Vector();
deleteFiles(readDeleteableFiles(), deletable); // try to delete deleteable
for (int i = 0; i < segments.size(); i++) {
SegmentReader reader = (SegmentReader)segments.elementAt(i);
if (reader.directory == this.directory)
deleteFiles(reader.files(), deletable); // try to delete our files
else
deleteFiles(reader.files(), reader.directory); // delete, eg, RAM files
}
writeDeleteableFiles(deletable); // note files we can't delete
}
private final void deleteFiles(Vector files, Directory directory)
throws IOException {
for (int i = 0; i < files.size(); i++)
directory.deleteFile((String)files.elementAt(i));
}
private final void deleteFiles(Vector files, Vector deletable)
throws IOException {
for (int i = 0; i < files.size(); i++) {
String file = (String)files.elementAt(i);
try {
directory.deleteFile(file); // try to delete each file
} catch (IOException e) { // if delete fails
if (directory.fileExists(file)) {
if (infoStream != null)
infoStream.println(e.getMessage() + "; Will re-try later.");
deletable.addElement(file); // add to deletable
}
}
}
}
private final Vector readDeleteableFiles() throws IOException {
Vector result = new Vector();
if (!directory.fileExists("deletable"))
return result;
InputStream input = directory.openFile("deletable");
try {
for (int i = input.readInt(); i > 0; i--) // read file names
result.addElement(input.readString());
} finally {
input.close();
}
return result;
}
private final void writeDeleteableFiles(Vector files) throws IOException {
OutputStream output = directory.createFile("deleteable.new");
try {
output.writeInt(files.size());
for (int i = 0; i < files.size(); i++)
output.writeString((String)files.elementAt(i));
} finally {
output.close();
}
directory.renameFile("deleteable.new", "deletable");
}
}