FileDocCategorySizeDatePackage
IndexWriter.javaAPI DocApache Lucene 1.929663Mon Feb 27 11:12:34 GMT 2006org.apache.lucene.index

IndexWriter

public class IndexWriter extends Object
An IndexWriter creates and maintains an index. The third argument to the constructor determines whether a new index is created, or whether an existing index is opened for the addition of new documents. In either case, documents are added with the addDocument method. When finished adding documents, close should be called.

If an index will not have more documents added for a while and optimal search performance is desired, then the optimize method should be called before the index is closed.

Opening an IndexWriter creates a lock file for the directory in use. Trying to open another IndexWriter on the same directory will lead to an IOException. The IOException is also thrown if an IndexReader on the same directory is used to delete documents from the index.

see
IndexModifier IndexModifier supports the important methods of IndexWriter plus deletion

Fields Summary
public static final long
WRITE_LOCK_TIMEOUT
Default value is 1,000.
public static final long
COMMIT_LOCK_TIMEOUT
Default value is 10,000.
public static final String
WRITE_LOCK_NAME
public static final String
COMMIT_LOCK_NAME
public static final int
DEFAULT_MERGE_FACTOR
Default value is 10. Change using {@link #setMergeFactor(int)}.
public static final int
DEFAULT_MAX_BUFFERED_DOCS
Default value is 10. Change using {@link #setMaxBufferedDocs(int)}.
public static final int
DEFAULT_MIN_MERGE_DOCS
public static final int
DEFAULT_MAX_MERGE_DOCS
Default value is {@link Integer#MAX_VALUE}. Change using {@link #setMaxMergeDocs(int)}.
public static final int
DEFAULT_MAX_FIELD_LENGTH
Default value is 10,000. Change using {@link #setMaxFieldLength(int)}.
public static final int
DEFAULT_TERM_INDEX_INTERVAL
Default value is 128. Change using {@link #setTermIndexInterval(int)}.
private Directory
directory
private Analyzer
analyzer
private Similarity
similarity
private SegmentInfos
segmentInfos
private final Directory
ramDirectory
private Lock
writeLock
private int
termIndexInterval
private boolean
useCompoundFile
Use compound file setting. Defaults to true, minimizing the number of files used. Setting this to false may improve indexing performance, but may also cause file handle problems.
private boolean
closeDir
public int
maxFieldLength
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.

Note that this effectively truncates large documents, excluding from the index terms that occur further in the document. If you know your source documents are large, be sure to set this value high enough to accomodate the expected size. If you set it to Integer.MAX_VALUE, then the only limit is your memory, but you should anticipate an OutOfMemoryError.

By default, no more than 10,000 terms will be indexed for a field.

public int
mergeFactor
Determines how often segment indices are merged by addDocument(). With smaller values, less RAM is used while indexing, and searches on unoptimized indices are faster, but indexing speed is slower. With larger values, more RAM is used during indexing, and while searches on unoptimized indices are slower, indexing is faster. Thus larger values (> 10) are best for batch index creation, and smaller values (< 10) for indices that are interactively maintained.

This must never be less than 2. The default value is 10.

public int
minMergeDocs
Determines the minimal number of documents required before the buffered in-memory documents are merging and a new Segment is created. Since Documents are merged in a {@link org.apache.lucene.store.RAMDirectory}, large value gives faster indexing. At the same time, mergeFactor limits the number of files open in a FSDirectory.

The default value is 10.

public int
maxMergeDocs
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.

The default value is {@link Integer#MAX_VALUE}.

public PrintStream
infoStream
If non-null, information about merges will be printed to this.
Constructors Summary
private IndexWriter(Directory d, Analyzer a, boolean create, boolean closeDir)

      this.closeDir = closeDir;
      directory = d;
      analyzer = a;

      Lock writeLock = directory.makeLock(IndexWriter.WRITE_LOCK_NAME);
      if (!writeLock.obtain(WRITE_LOCK_TIMEOUT)) // obtain write lock
        throw new IOException("Index locked for write: " + writeLock);
      this.writeLock = writeLock;                   // save it

      synchronized (directory) {        // in- & inter-process sync
        new Lock.With(directory.makeLock(IndexWriter.COMMIT_LOCK_NAME), COMMIT_LOCK_TIMEOUT) {
            public Object doBody() throws IOException {
              if (create)
                segmentInfos.write(directory);
              else
                segmentInfos.read(directory);
              return null;
            }
          }.run();
      }
public IndexWriter(String path, Analyzer a, boolean create)
Constructs an IndexWriter for the index in path. Text will be analyzed with a. If create is true, then a new, empty index will be created in path, replacing the index already there, if any.

param
path the path to the index directory
param
a the analyzer to use
param
create true to create the index or overwrite the existing one; false to append to the existing index
throws
IOException if the directory cannot be read/written to, or if it does not exist, and create is false

    this(FSDirectory.getDirectory(path, create), a, create, true);
public IndexWriter(File path, Analyzer a, boolean create)
Constructs an IndexWriter for the index in path. Text will be analyzed with a. If create is true, then a new, empty index will be created in path, replacing the index already there, if any.

param
path the path to the index directory
param
a the analyzer to use
param
create true to create the index or overwrite the existing one; false to append to the existing index
throws
IOException if the directory cannot be read/written to, or if it does not exist, and create is false

    this(FSDirectory.getDirectory(path, create), a, create, true);
public IndexWriter(Directory d, Analyzer a, boolean create)
Constructs an IndexWriter for the index in d. Text will be analyzed with a. If create is true, then a new, empty index will be created in d, replacing the index already there, if any.

param
d the index directory
param
a the analyzer to use
param
create true to create the index or overwrite the existing one; false to append to the existing index
throws
IOException if the directory cannot be read/written to, or if it does not exist, and create is false

    this(d, a, create, false);
Methods Summary
public voidaddDocument(org.apache.lucene.document.Document doc)
Adds a document to this index. If the document contains more than {@link #setMaxFieldLength(int)} terms for a given field, the remainder are discarded.


                             
        
    addDocument(doc, analyzer);
public voidaddDocument(org.apache.lucene.document.Document doc, org.apache.lucene.analysis.Analyzer analyzer)
Adds a document to this index, using the provided analyzer instead of the value of {@link #getAnalyzer()}. If the document contains more than {@link #setMaxFieldLength(int)} terms for a given field, the remainder are discarded.

    DocumentWriter dw =
      new DocumentWriter(ramDirectory, analyzer, this);
    dw.setInfoStream(infoStream);
    String segmentName = newSegmentName();
    dw.addDocument(segmentName, doc);
    synchronized (this) {
      segmentInfos.addElement(new SegmentInfo(segmentName, 1, ramDirectory));
      maybeMergeSegments();
    }
public synchronized voidaddIndexes(org.apache.lucene.store.Directory[] dirs)
Merges all segments from an array of indexes into this index.

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.

After this completes, the index is optimized.

    optimize();					  // start with zero or 1 seg

    int start = segmentInfos.size();

    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 newly added segments in log(n) passes
    while (segmentInfos.size() > start+mergeFactor) {
      for (int base = start+1; base < segmentInfos.size(); base++) {
        int end = Math.min(segmentInfos.size(), base+mergeFactor);
        if (end-base > 1)
          mergeSegments(base, end);
      }
    }

    optimize();					  // final cleanup
public synchronized voidaddIndexes(org.apache.lucene.index.IndexReader[] readers)
Merges the provided indexes into this index.

After this completes, the index is optimized.

The provided IndexReaders are not closed.


    optimize();					  // start with zero or 1 seg

    final String mergedName = newSegmentName();
    SegmentMerger merger = new SegmentMerger(this, mergedName);

    final Vector segmentsToDelete = new Vector();
    IndexReader sReader = null;
    if (segmentInfos.size() == 1){ // add existing index, if any
        sReader = SegmentReader.get(segmentInfos.info(0));
        merger.add(sReader);
        segmentsToDelete.addElement(sReader);   // queue segment for deletion
    }
      
    for (int i = 0; i < readers.length; i++)      // add new indexes
      merger.add(readers[i]);

    int docCount = merger.merge();                // merge 'em

    segmentInfos.setSize(0);                      // pop old infos & add new
    segmentInfos.addElement(new SegmentInfo(mergedName, docCount, directory));
    
    if(sReader != null)
        sReader.close();

    synchronized (directory) {			  // in- & inter-process sync
      new Lock.With(directory.makeLock(COMMIT_LOCK_NAME), COMMIT_LOCK_TIMEOUT) {
	  public Object doBody() throws IOException {
	    segmentInfos.write(directory);	  // commit changes
	    deleteSegments(segmentsToDelete);  // delete now-unused segments
	    return null;
	  }
	}.run();
    }
    
    if (useCompoundFile) {
      final Vector filesToDelete = merger.createCompoundFile(mergedName + ".tmp");
      synchronized (directory) { // in- & inter-process sync
        new Lock.With(directory.makeLock(COMMIT_LOCK_NAME), COMMIT_LOCK_TIMEOUT) {
          public Object doBody() throws IOException {
            // make compound file visible for SegmentReaders
            directory.renameFile(mergedName + ".tmp", mergedName + ".cfs");
            // delete now unused files of segment 
            deleteFiles(filesToDelete);   
            return null;
          }
        }.run();
      }
    }
public synchronized voidclose()
Flushes all changes to an index and closes all associated files.

    flushRamSegments();
    ramDirectory.close();
    if (writeLock != null) {
      writeLock.release();                          // release write lock
      writeLock = null;
    }
    if(closeDir)
      directory.close();
private final voiddeleteFiles(java.util.Vector files)

    Vector deletable = new Vector();
    deleteFiles(readDeleteableFiles(), deletable); // try to delete deleteable
    deleteFiles(files, deletable);     // try to delete our files
    writeDeleteableFiles(deletable);        // note files we can't delete
private final voiddeleteFiles(java.util.Vector files, org.apache.lucene.store.Directory directory)

    for (int i = 0; i < files.size(); i++)
      directory.deleteFile((String)files.elementAt(i));
private final voiddeleteFiles(java.util.Vector files, java.util.Vector deletable)

    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.toString() + "; Will re-try later.");
          deletable.addElement(file);		  // add to deletable
        }
      }
    }
private final voiddeleteSegments(java.util.Vector segments)

    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 other files
    }

    writeDeleteableFiles(deletable);		  // note files we can't delete
public synchronized intdocCount()
Returns the number of documents currently in this index.

    int count = 0;
    for (int i = 0; i < segmentInfos.size(); i++) {
      SegmentInfo si = segmentInfos.info(i);
      count += si.docCount;
    }
    return count;
protected voidfinalize()
Release the write lock, if needed.

    if (writeLock != null) {
      writeLock.release();                        // release write lock
      writeLock = null;
    }
private final voidflushRamSegments()
Merges all RAM-resident segments.

    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);
public org.apache.lucene.analysis.AnalyzergetAnalyzer()
Returns the analyzer used by this index.

      return analyzer;
public org.apache.lucene.store.DirectorygetDirectory()
Returns the Directory used by this index.

      return directory;
public java.io.PrintStreamgetInfoStream()

see
#setInfoStream

    return infoStream;
public intgetMaxBufferedDocs()

see
#setMaxBufferedDocs

    return minMergeDocs;
public intgetMaxFieldLength()

see
#setMaxFieldLength

    return maxFieldLength;
public intgetMaxMergeDocs()

see
#setMaxMergeDocs

    return maxMergeDocs;
public intgetMergeFactor()

see
#setMergeFactor

    return mergeFactor;
final intgetSegmentsCounter()

    return segmentInfos.counter;
public org.apache.lucene.search.SimilaritygetSimilarity()
Expert: Return the Similarity implementation used by this IndexWriter.

This defaults to the current value of {@link Similarity#getDefault()}.

    return this.similarity;
public intgetTermIndexInterval()
Expert: Return the interval between indexed terms.

see
#setTermIndexInterval(int)

 return termIndexInterval;
public booleangetUseCompoundFile()
Get the current setting of whether to use the compound file format. Note that this just returns the value you set with setUseCompoundFile(boolean) or the default. You cannot use this to query the status of an existing index.

see
#setUseCompoundFile(boolean)


                                                
     
    return useCompoundFile;
private final voidmaybeMergeSegments()
Incremental segment merger.

    long targetMergeDocs = minMergeDocs;
    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
    }
private final voidmergeSegments(int minSegment)
Pops segments off of segmentInfos stack down to minSegment, merges them, and pushes the merged index onto the top of the segmentInfos stack.

    mergeSegments(minSegment, segmentInfos.size());
private final voidmergeSegments(int minSegment, int end)
Merges the named range of segments, replacing them in the stack with a single segment.

    final String mergedName = newSegmentName();
    if (infoStream != null) infoStream.print("merging segments");
    SegmentMerger merger = new SegmentMerger(this, mergedName);

    final Vector segmentsToDelete = new Vector();
    for (int i = minSegment; i < end; i++) {
      SegmentInfo si = segmentInfos.info(i);
      if (infoStream != null)
        infoStream.print(" " + si.name + " (" + si.docCount + " docs)");
      IndexReader reader = SegmentReader.get(si);
      merger.add(reader);
      if ((reader.directory() == this.directory) || // if we own the directory
          (reader.directory() == this.ramDirectory))
        segmentsToDelete.addElement(reader);   // queue segment for deletion
    }

    int mergedDocCount = merger.merge();

    if (infoStream != null) {
      infoStream.println(" into "+mergedName+" ("+mergedDocCount+" docs)");
    }

    for (int i = end-1; i >= minSegment; i--)     // remove old infos & add new
      segmentInfos.remove(i);
    segmentInfos.addElement(new SegmentInfo(mergedName, mergedDocCount,
                                            directory));

    // close readers before we attempt to delete now-obsolete segments
    merger.closeReaders();

    synchronized (directory) {                 // in- & inter-process sync
      new Lock.With(directory.makeLock(COMMIT_LOCK_NAME), COMMIT_LOCK_TIMEOUT) {
          public Object doBody() throws IOException {
            segmentInfos.write(directory);     // commit before deleting
            deleteSegments(segmentsToDelete);  // delete now-unused segments
            return null;
          }
        }.run();
    }
    
    if (useCompoundFile) {
      final Vector filesToDelete = merger.createCompoundFile(mergedName + ".tmp");
      synchronized (directory) { // in- & inter-process sync
        new Lock.With(directory.makeLock(COMMIT_LOCK_NAME), COMMIT_LOCK_TIMEOUT) {
          public Object doBody() throws IOException {
            // make compound file visible for SegmentReaders
            directory.renameFile(mergedName + ".tmp", mergedName + ".cfs");
            // delete now unused files of segment 
            deleteFiles(filesToDelete);   
            return null;
          }
        }.run();
      }
    }
private final synchronized java.lang.StringnewSegmentName()

    return "_" + Integer.toString(segmentInfos.counter++, Character.MAX_RADIX);
public synchronized voidoptimize()
Merges all segments together into a single segment, optimizing an index for search.


                     
        
    flushRamSegments();
    while (segmentInfos.size() > 1 ||
           (segmentInfos.size() == 1 &&
            (SegmentReader.hasDeletions(segmentInfos.info(0)) ||
             segmentInfos.info(0).dir != directory ||
             (useCompoundFile &&
              (!SegmentReader.usesCompoundFile(segmentInfos.info(0)) ||
                SegmentReader.hasSeparateNorms(segmentInfos.info(0))))))) {
      int minSegment = segmentInfos.size() - mergeFactor;
      mergeSegments(minSegment < 0 ? 0 : minSegment);
    }
private final java.util.VectorreadDeleteableFiles()

    Vector result = new Vector();
    if (!directory.fileExists(IndexFileNames.DELETABLE))
      return result;

    IndexInput input = directory.openInput(IndexFileNames.DELETABLE);
    try {
      for (int i = input.readInt(); i > 0; i--)	  // read file names
        result.addElement(input.readString());
    } finally {
      input.close();
    }
    return result;
public voidsetInfoStream(java.io.PrintStream infoStream)
If non-null, information about merges and a message when maxFieldLength is reached will be printed to this.

    this.infoStream = infoStream;
public voidsetMaxBufferedDocs(int maxBufferedDocs)
Determines the minimal number of documents required before the buffered in-memory documents are merging and a new Segment is created. Since Documents are merged in a {@link org.apache.lucene.store.RAMDirectory}, large value gives faster indexing. At the same time, mergeFactor limits the number of files open in a FSDirectory.

The default value is 10.

throws
IllegalArgumentException if maxBufferedDocs is smaller than 2

    if (maxBufferedDocs < 2)
      throw new IllegalArgumentException("maxBufferedDocs must at least be 2");
    this.minMergeDocs = maxBufferedDocs;
public voidsetMaxFieldLength(int maxFieldLength)
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.

Note that this effectively truncates large documents, excluding from the index terms that occur further in the document. If you know your source documents are large, be sure to set this value high enough to accomodate the expected size. If you set it to Integer.MAX_VALUE, then the only limit is your memory, but you should anticipate an OutOfMemoryError.

By default, no more than 10,000 terms will be indexed for a field.

    this.maxFieldLength = maxFieldLength;
public voidsetMaxMergeDocs(int maxMergeDocs)
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.

The default value is {@link Integer#MAX_VALUE}.

    this.maxMergeDocs = maxMergeDocs;
public voidsetMergeFactor(int mergeFactor)
Determines how often segment indices are merged by addDocument(). With smaller values, less RAM is used while indexing, and searches on unoptimized indices are faster, but indexing speed is slower. With larger values, more RAM is used during indexing, and while searches on unoptimized indices are slower, indexing is faster. Thus larger values (> 10) are best for batch index creation, and smaller values (< 10) for indices that are interactively maintained.

This must never be less than 2. The default value is 10.

    if (mergeFactor < 2)
      throw new IllegalArgumentException("mergeFactor cannot be less than 2");
    this.mergeFactor = mergeFactor;
public voidsetSimilarity(org.apache.lucene.search.Similarity similarity)
Expert: Set the Similarity implementation used by this IndexWriter.

see
Similarity#setDefault(Similarity)

    this.similarity = similarity;
public voidsetTermIndexInterval(int interval)
Expert: Set the interval between indexed terms. Large values cause less memory to be used by IndexReader, but slow random-access to terms. Small values cause more memory to be used by an IndexReader, and speed random-access to terms. This parameter determines the amount of computation required per query term, regardless of the number of documents that contain that term. In particular, it is the maximum number of other terms that must be scanned before a term is located and its frequency and position information may be processed. In a large index with user-entered query terms, query processing time is likely to be dominated not by term lookup but rather by the processing of frequency and positional data. In a small index or when many uncommon query terms are generated (e.g., by wildcard queries) term lookup may become a dominant cost. In particular, numUniqueTerms/interval terms are read into memory by an IndexReader, and, on average, interval/2 terms must be scanned for each random term access.

see
#DEFAULT_TERM_INDEX_INTERVAL

    this.termIndexInterval = interval;
public voidsetUseCompoundFile(boolean value)
Setting to turn on usage of a compound file. When on, multiple files for each segment are merged into a single file once the segment creation is finished. This is done regardless of what directory is in use.

    useCompoundFile = value;
private final voidwriteDeleteableFiles(java.util.Vector files)

    IndexOutput output = directory.createOutput("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", IndexFileNames.DELETABLE);