Also see:

setDefaultWriteLockTimeout

Also see:

LogMergePolicy#DEFAULT_MERGE_FACTOR

Also see:

LogDocMergePolicy#DEFAULT_MAX_MERGE_DOCS

 public IndexWriter(String path,
    Analyzer a) throws IOException, CorruptIndexException, LockObtainFailedException 
{
    init(FSDirectory.getDirectory(path), a, true, null, true);
}

Constructs an IndexWriter for the index in path, first creating it if it does not already exist. Text will be analyzed with a.

Parameters:

path - the path to the index directory

a - the analyzer to use

Throws:

CorruptIndexException - if the index is corrupt

LockObtainFailedException - if another writer has this index open (write.lock could not be obtained)

IOException - if the directory cannot be read/written to or if there is any other low-level IO error

 public IndexWriter(File path,
    Analyzer a) throws IOException, CorruptIndexException, LockObtainFailedException 
{
    init(FSDirectory.getDirectory(path), a, true, null, true);
}

Constructs an IndexWriter for the index in path, first creating it if it does not already exist. Text will be analyzed with a.

Parameters:

path - the path to the index directory

a - the analyzer to use

Throws:

CorruptIndexException - if the index is corrupt

LockObtainFailedException - if another writer has this index open (write.lock could not be obtained)

IOException - if the directory cannot be read/written to or if there is any other low-level IO error

 public IndexWriter(Directory d,
    Analyzer a) throws IOException, CorruptIndexException, LockObtainFailedException 
{
    init(d, a, false, null, true);
}

Constructs an IndexWriter for the index in d, first creating it if it does not already exist. Text will be analyzed with a.

Parameters:

d - the index directory

a - the analyzer to use

Throws:

CorruptIndexException - if the index is corrupt

LockObtainFailedException - if another writer has this index open (write.lock could not be obtained)

IOException - if the directory cannot be read/written to or if there is any other low-level IO error

 public IndexWriter(String path,
    Analyzer a,
    boolean create) throws IOException, CorruptIndexException, LockObtainFailedException 
{
    init(FSDirectory.getDirectory(path), a, create, true, null, true);
}

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.

Parameters:

path - the path to the index directory

a - the analyzer to use

create - true to create the index or overwrite the existing one; false to append to the existing index

Throws:

CorruptIndexException - if the index is corrupt

LockObtainFailedException - if another writer has this index open (write.lock could not be obtained)

IOException - if the directory cannot be read/written to, or if it does not exist and create is false or if there is any other low-level IO error

 public IndexWriter(File path,
    Analyzer a,
    boolean create) throws IOException, CorruptIndexException, LockObtainFailedException 
{
    init(FSDirectory.getDirectory(path), a, create, true, null, true);
}

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.

Parameters:

path - the path to the index directory

a - the analyzer to use

create - true to create the index or overwrite the existing one; false to append to the existing index

Throws:

CorruptIndexException - if the index is corrupt

LockObtainFailedException - if another writer has this index open (write.lock could not be obtained)

IOException - if the directory cannot be read/written to, or if it does not exist and create is false or if there is any other low-level IO error

 public IndexWriter(Directory d,
    Analyzer a,
    boolean create) throws IOException, CorruptIndexException, LockObtainFailedException 
{
    init(d, a, create, false, null, true);
}

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.

Parameters:

d - the index directory

a - the analyzer to use

create - true to create the index or overwrite the existing one; false to append to the existing index

Throws:

CorruptIndexException - if the index is corrupt

LockObtainFailedException - if another writer has this index open (write.lock could not be obtained)

IOException - if the directory cannot be read/written to, or if it does not exist and create is false or if there is any other low-level IO error

 public IndexWriter(Directory d,
    boolean autoCommit,
    Analyzer a) throws IOException, CorruptIndexException, LockObtainFailedException 
{
    init(d, a, false, null, autoCommit);
}

Constructs an IndexWriter for the index in d, first creating it if it does not already exist. Text will be analyzed with a.

Parameters:

d - the index directory

autoCommit - see above

a - the analyzer to use

Throws:

CorruptIndexException - if the index is corrupt

LockObtainFailedException - if another writer has this index open (write.lock could not be obtained)

IOException - if the directory cannot be read/written to or if there is any other low-level IO error

 public IndexWriter(Directory d,
    boolean autoCommit,
    Analyzer a,
    boolean create) throws IOException, CorruptIndexException, LockObtainFailedException 
{
    init(d, a, create, false, null, autoCommit);
}

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.

Parameters:

d - the index directory

autoCommit - see above

a - the analyzer to use

create - true to create the index or overwrite the existing one; false to append to the existing index

Throws:

CorruptIndexException - if the index is corrupt

LockObtainFailedException - if another writer has this index open (write.lock could not be obtained)

IOException - if the directory cannot be read/written to, or if it does not exist and create is false or if there is any other low-level IO error

 public IndexWriter(Directory d,
    boolean autoCommit,
    Analyzer a,
    IndexDeletionPolicy deletionPolicy) throws IOException, CorruptIndexException, LockObtainFailedException 
{
    init(d, a, false, deletionPolicy, autoCommit);
}

Expert: constructs an IndexWriter with a custom IndexDeletionPolicy , for the index in d, first creating it if it does not already exist. Text will be analyzed with a.

Parameters:

d - the index directory

autoCommit - see above

a - the analyzer to use

deletionPolicy - see above

Throws:

CorruptIndexException - if the index is corrupt

LockObtainFailedException - if another writer has this index open (write.lock could not be obtained)

IOException - if the directory cannot be read/written to or if there is any other low-level IO error

 public IndexWriter(Directory d,
    boolean autoCommit,
    Analyzer a,
    boolean create,
    IndexDeletionPolicy deletionPolicy) throws IOException, CorruptIndexException, LockObtainFailedException 
{
    init(d, a, create, false, deletionPolicy, autoCommit);
}

Expert: constructs an IndexWriter with a custom IndexDeletionPolicy , 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.

Parameters:

d - the index directory

autoCommit - see above

a - the analyzer to use

create - true to create the index or overwrite the existing one; false to append to the existing index

deletionPolicy - see above

Throws:

CorruptIndexException - if the index is corrupt

LockObtainFailedException - if another writer has this index open (write.lock could not be obtained)

IOException - if the directory cannot be read/written to, or if it does not exist and create is false or if there is any other low-level IO error

 public  void abort() throws IOException 
{
    ensureOpen();
    if (autoCommit)
      throw new IllegalStateException("abort() can only be called when IndexWriter was opened with autoCommit=false");
    boolean doClose;
    synchronized(this) {
      // Ensure that only one thread actually gets to do the closing:
      if (!closing) {
        doClose = true;
        closing = true;
      } else
        doClose = false;
    }
    if (doClose) {
      finishMerges(false);
      // Must pre-close these two, in case they set
      // commitPending=true, so that we can then set it to
      // false before calling closeInternal
      mergePolicy.close();
      mergeScheduler.close();
      synchronized(this) {
        // Keep the same segmentInfos instance but replace all
        // of its SegmentInfo instances.  This is so the next
        // attempt to commit using this instance of IndexWriter
        // will always write to a new generation ("write
        // once").
        segmentInfos.clear();
        segmentInfos.addAll(rollbackSegmentInfos);
        docWriter.abort(null);
        // Ask deleter to locate unreferenced files & remove
        // them:
        deleter.checkpoint(segmentInfos, false);
        deleter.refresh();
      }
      commitPending = false;
      closeInternal(false);
    } else
      waitForClose();
}

Close the IndexWriter without committing any of the changes that have occurred since it was opened. This removes any temporary files that had been created, after which the state of the index will be the same as it was when this writer was first opened. This can only be called when this IndexWriter was opened with autoCommit=false.

 public  void addDocument(Document doc) throws IOException, CorruptIndexException 
{
                                                                                                                                                                                                                                                
    addDocument(doc, analyzer);
}

Adds a document to this index. If the document contains more than #setMaxFieldLength(int) terms for a given field, the remainder are discarded.

Note that if an Exception is hit (for example disk full) then the index will be consistent, but this document may not have been added. Furthermore, it's possible the index will have one segment in non-compound format even when using compound files (when a merge has partially succeeded).

This method periodically flushes pending documents to the Directory (every #setMaxBufferedDocs ), and also periodically merges segments in the index (every #setMergeFactor flushes). When this occurs, the method will take more time to run (possibly a long time if the index is large), and will require free temporary space in the Directory to do the merging.

The amount of free space required when a merge is triggered is up to 1X the size of all segments being merged, when no readers/searchers are open against the index, and up to 2X the size of all segments being merged when readers/searchers are open against the index (see #optimize() for details). The sequence of primitive merge operations performed is governed by the merge policy.

Note that each term in the document can be no longer than 16383 characters, otherwise an IllegalArgumentException will be thrown.

 public  void addDocument(Document doc,
    Analyzer analyzer) throws IOException, CorruptIndexException 
{
    ensureOpen();
    boolean doFlush = false;
    boolean success = false;
    try {
      try {
        doFlush = docWriter.addDocument(doc, analyzer);
        success = true;
      } finally {
        if (!success) {
          if (infoStream != null)
            message("hit exception adding document");
          synchronized (this) {
            // If docWriter has some aborted files that were
            // never incref'd, then we clean them up here
            if (docWriter != null) {
              final List files = docWriter.abortedFiles();
              if (files != null)
                deleter.deleteNewFiles(files);
            }
          }
        }
      }
      if (doFlush)
        flush(true, false);
    } catch (OutOfMemoryError oom) {
      hitOOM = true;
      throw oom;
    }
}

Adds a document to this index, using the provided analyzer instead of the value of #getAnalyzer() . If the document contains more than #setMaxFieldLength(int) terms for a given field, the remainder are discarded.

See #addDocument(Document) for details on index and IndexWriter state after an Exception, and flushing/merging temporary free space requirements.

 public  void addIndexes(Directory[] dirs) throws IOException, CorruptIndexException 
{
    ensureOpen();
    // Do not allow add docs or deletes while we are running:
    docWriter.pauseAllThreads();
    try {
      if (infoStream != null)
        message("flush at addIndexes");
      flush();
      boolean success = false;
      startTransaction();
      try {
        synchronized(this) {
          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++) {
              final SegmentInfo info = sis.info(j);
              segmentInfos.addElement(sis.info(j));	  // add each info
            }
          }
        }
        optimize();
        success = true;
      } finally {
        if (success) {
          commitTransaction();
        } else {
          rollbackTransaction();
        }
      }
    } catch (OutOfMemoryError oom) {
      hitOOM = true;
      throw oom;
    } finally {
      docWriter.resumeAllThreads();
    }
}

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.

NOTE: the index in each Directory must not be changed (opened by a writer) while this method is running. This method does not acquire a write lock in each input Directory, so it is up to the caller to enforce this.

NOTE: while this is running, any attempts to add or delete documents (with another thread) will be paused until this method completes.

After this completes, the index is optimized.

This method is transactional in how Exceptions are handled: it does not commit a new segments_N file until all indexes are added. This means if an Exception occurs (for example disk full), then either no indexes will have been added or they all will have been.

If an Exception is hit, it's still possible that all indexes were successfully added. This happens when the Exception is hit when trying to build a CFS file. In this case, one segment in the index will be in non-CFS format, even when using compound file format.

Also note that on an Exception, the index may still have been partially or fully optimized even though none of the input indexes were added.

Note that this requires temporary free space in the Directory up to 2X the sum of all input indexes (including the starting index). If readers/searchers are open against the starting index, then temporary free space required will be higher by the size of the starting index (see #optimize() for details).

Once this completes, the final size of the index will be less than the sum of all input index sizes (including the starting index). It could be quite a bit smaller (if there were many pending deletes) or just slightly smaller.

See LUCENE-702 for details.

 public  void addIndexes(IndexReader[] readers) throws IOException, CorruptIndexException 
{
    ensureOpen();
    // Do not allow add docs or deletes while we are running:
    docWriter.pauseAllThreads();
    try {
      optimize();					  // start with zero or 1 seg
      final String mergedName = newSegmentName();
      SegmentMerger merger = new SegmentMerger(this, mergedName, null);
      SegmentInfo info;
      IndexReader sReader = null;
      try {
        synchronized(this) {
          if (segmentInfos.size() == 1){ // add existing index, if any
            sReader = SegmentReader.get(segmentInfos.info(0));
            merger.add(sReader);
          }
        }
        for (int i = 0; i <  readers.length; i++)      // add new indexes
          merger.add(readers[i]);
        boolean success = false;
        startTransaction();
        try {
          int docCount = merger.merge();                // merge 'em
          if(sReader != null) {
            sReader.close();
            sReader = null;
          }
          synchronized(this) {
            segmentInfos.setSize(0);                      // pop old infos & add new
            info = new SegmentInfo(mergedName, docCount, directory, false, true,
                                   -1, null, false);
            segmentInfos.addElement(info);
          }
          success = true;
        } finally {
          if (!success) {
            if (infoStream != null)
              message("hit exception in addIndexes during merge");
            rollbackTransaction();
          } else {
            commitTransaction();
          }
        }
      } finally {
        if (sReader != null) {
          sReader.close();
        }
      }
      if (mergePolicy instanceof LogMergePolicy && getUseCompoundFile()) {
        boolean success = false;
        startTransaction();
        try {
          merger.createCompoundFile(mergedName + ".cfs");
          synchronized(this) {
            info.setUseCompoundFile(true);
          }
		  success = true;
        } finally {
          if (!success) {
            if (infoStream != null)
              message("hit exception building compound file in addIndexes during merge");
            rollbackTransaction();
          } else {
            commitTransaction();
          }
        }
      }
    } catch (OutOfMemoryError oom) {
      hitOOM = true;
      throw oom;
    } finally {
      docWriter.resumeAllThreads();
    }
}

Merges the provided indexes into this index.

After this completes, the index is optimized.

The provided IndexReaders are not closed.

NOTE: the index in each Directory must not be changed (opened by a writer) while this method is running. This method does not acquire a write lock in each input Directory, so it is up to the caller to enforce this.

NOTE: while this is running, any attempts to add or delete documents (with another thread) will be paused until this method completes.

See #addIndexes(Directory[]) for details on transactional semantics, temporary free space required in the Directory, and non-CFS segments on an Exception.

 public  void addIndexesNoOptimize(Directory[] dirs) throws IOException, CorruptIndexException 
{
    ensureOpen();
    // Do not allow add docs or deletes while we are running:
    docWriter.pauseAllThreads();
    try {
      if (infoStream != null)
        message("flush at addIndexesNoOptimize");
      flush();
      boolean success = false;
      startTransaction();
      try {
        synchronized(this) {
          for (int i = 0; i <  dirs.length; i++) {
            if (directory == dirs[i]) {
              // cannot add this index: segments may be deleted in merge before added
              throw new IllegalArgumentException("Cannot add this index to itself");
            }
            SegmentInfos sis = new SegmentInfos(); // read infos from dir
            sis.read(dirs[i]);
            for (int j = 0; j <  sis.size(); j++) {
              SegmentInfo info = sis.info(j);
              segmentInfos.addElement(info); // add each info
            }
          }
        }
        maybeMerge();
        // If after merging there remain segments in the index
        // that are in a different directory, just copy these
        // over into our index.  This is necessary (before
        // finishing the transaction) to avoid leaving the
        // index in an unusable (inconsistent) state.
        copyExternalSegments();
        success = true;
      } finally {
        if (success) {
          commitTransaction();
        } else {
          rollbackTransaction();
        }
      }
    } catch (OutOfMemoryError oom) {
      hitOOM = true;
      throw oom;
    } finally {
      docWriter.resumeAllThreads();
    }
}

Merges all segments from an array of indexes into this index.

This is similar to addIndexes(Directory[]). However, no optimize() is called either at the beginning or at the end. Instead, merges are carried out as necessary.

NOTE: the index in each Directory must not be changed (opened by a writer) while this method is running. This method does not acquire a write lock in each input Directory, so it is up to the caller to enforce this.

NOTE: while this is running, any attempts to add or delete documents (with another thread) will be paused until this method completes.

This requires this index not be among those to be added, and the upper bound* of those segment doc counts not exceed maxMergeDocs.

See #addIndexes(Directory[]) for details on transactional semantics, temporary free space required in the Directory, and non-CFS segments on an Exception.

 synchronized  void addMergeException(MergePolicy.OneMerge merge) 
{
    if (!mergeExceptions.contains(merge) && mergeGen == merge.mergeGen)
      mergeExceptions.add(merge);
}

 public  void close() throws IOException, CorruptIndexException 
{
    close(true);
}

Flushes all changes to an index and closes all associated files.

If an Exception is hit during close, eg due to disk full or some other reason, then both the on-disk index and the internal state of the IndexWriter instance will be consistent. However, the close will not be complete even though part of it (flushing buffered documents) may have succeeded, so the write lock will still be held.

If you can correct the underlying cause (eg free up some disk space) then you can call close() again. Failing that, if you want to force the write lock to be released (dangerous, because you may then lose buffered docs in the IndexWriter instance) then you can do something like this:

try {
writer.close();
} finally {
if (IndexReader.isLocked(directory)) {
IndexReader.unlock(directory);
}
}

after which, you must be certain not to use the writer instance anymore.

 public  void close(boolean waitForMerges) throws IOException, CorruptIndexException 
{
    boolean doClose;
    // If any methods have hit OutOfMemoryError, then abort
    // on close, in case the internal state of IndexWriter
    // or DocumentsWriter is corrupt
    if (hitOOM)
      abort();
    synchronized(this) {
      // Ensure that only one thread actually gets to do the closing:
      if (!closing) {
        doClose = true;
        closing = true;
      } else
        doClose = false;
    }
    if (doClose)
      closeInternal(waitForMerges);
    else
      // Another thread beat us to it (is actually doing the
      // close), so we will block until that other thread
      // has finished closing
      waitForClose();
}

Closes the index with or without waiting for currently running merges to finish. This is only meaningful when using a MergeScheduler that runs merges in background threads.

 public  void deleteDocuments(Term term) throws IOException, CorruptIndexException 
{
    ensureOpen();
    try {
      boolean doFlush = docWriter.bufferDeleteTerm(term);
      if (doFlush)
        flush(true, false);
    } catch (OutOfMemoryError oom) {
      hitOOM = true;
      throw oom;
    }
}

Deletes the document(s) containing term.

 public  void deleteDocuments(Term[] terms) throws IOException, CorruptIndexException 
{
    ensureOpen();
    try {
      boolean doFlush = docWriter.bufferDeleteTerms(terms);
      if (doFlush)
        flush(true, false);
    } catch (OutOfMemoryError oom) {
      hitOOM = true;
      throw oom;
    }
}

Deletes the document(s) containing any of the terms. All deletes are flushed at the same time.

  void doAfterFlush() throws IOException 
{

}

 public synchronized int docCount() 
{
    ensureOpen();
    int count = docWriter.getNumDocsInRAM();
    for (int i = 0; i <  segmentInfos.size(); i++) {
      SegmentInfo si = segmentInfos.info(i);
      count += si.docCount;
    }
    return count;
}

Returns the number of documents currently in this index.

 protected final  void ensureOpen() throws AlreadyClosedException 
{
                        
    if (closed) {
      throw new AlreadyClosedException("this IndexWriter is closed");
    }
}

Used internally to throw an AlreadyClosedException if this IndexWriter has been closed.

 protected  void finalize() throws Throwable 
{
    try {
      if (writeLock != null) {
        writeLock.release();                        // release write lock
        writeLock = null;
      }
    } finally {
      super.finalize();
    }
}

Release the write lock, if needed.

 public final  void flush() throws IOException, CorruptIndexException 
{
  
    flush(true, false);
}

Flush all in-memory buffered updates (adds and deletes) to the Directory.

Note: if autoCommit=false, flushed data would still not be visible to readers, until #close is called.

 protected final  void flush(boolean triggerMerge,
    boolean flushDocStores) throws IOException, CorruptIndexException 
{
    ensureOpen();
    if (doFlush(flushDocStores) && triggerMerge)
      maybeMerge();
}

Flush all in-memory buffered udpates (adds and deletes) to the Directory.

 public Analyzer getAnalyzer() 
{
    ensureOpen();
    return analyzer;
}

Returns the analyzer used by this index.

 final synchronized int getBufferedDeleteTermsSize() 
{
    return docWriter.getBufferedDeleteTerms().size();
}

 public static PrintStream getDefaultInfoStream() 
{
    return IndexWriter.defaultInfoStream;
}

Returns the current default infoStream for newly instantiated IndexWriters.

 public static long getDefaultWriteLockTimeout() 
{
    return IndexWriter.WRITE_LOCK_TIMEOUT;
}

Returns default write lock timeout for newly instantiated IndexWriters.

 public Directory getDirectory() 
{
    ensureOpen();
    return directory;
}

Returns the Directory used by this index.

 final synchronized int getDocCount(int i) 
{
    if (i  >= 0 && i <  segmentInfos.size()) {
      return segmentInfos.info(i).docCount;
    } else {
      return -1;
    }
}

 public PrintStream getInfoStream() 
{
    ensureOpen();
    return infoStream;
}

Returns the current infoStream in use by this writer.

 public int getMaxBufferedDeleteTerms() 
{
    ensureOpen();
    return docWriter.getMaxBufferedDeleteTerms();
}

Returns the number of buffered deleted terms that will trigger a flush if enabled.

 public int getMaxBufferedDocs() 
{
    ensureOpen();
    return docWriter.getMaxBufferedDocs();
}

Returns the number of buffered added documents that will trigger a flush if enabled.

 public int getMaxFieldLength() 
{
    ensureOpen();
    return maxFieldLength;
}

Returns the maximum number of terms that will be indexed for a single field in a document.

 public int getMaxMergeDocs() 
{
    return getLogMergePolicy().getMaxMergeDocs();
}

Returns the largest segment (measured by document count) that may be merged with other segments.

Note that this method is a convenience method: it just calls mergePolicy.getMaxMergeDocs as long as mergePolicy is an instance of LogMergePolicy . Otherwise an IllegalArgumentException is thrown.

 public int getMergeFactor() 
{
    return getLogMergePolicy().getMergeFactor();
}

Returns the number of segments that are merged at once and also controls the total number of segments allowed to accumulate in the index.

Note that this method is a convenience method: it just calls mergePolicy.getMergeFactor as long as mergePolicy is an instance of LogMergePolicy . Otherwise an IllegalArgumentException is thrown.

 public MergePolicy getMergePolicy() 
{
    ensureOpen();
    return mergePolicy;
}

Expert: returns the current MergePolicy in use by this writer.

 public MergeScheduler getMergeScheduler() 
{
    ensureOpen();
    return mergeScheduler;
}

Expert: returns the current MergePolicy in use by this writer.

 synchronized MergePolicy.OneMerge getNextMerge() 
{
    if (pendingMerges.size() == 0)
      return null;
    else {
      // Advance the merge from pending to running
      MergePolicy.OneMerge merge = (MergePolicy.OneMerge) pendingMerges.removeFirst();
      runningMerges.add(merge);
      return merge;
    }
}

Expert: the MergeScheduler calls this method to retrieve the next merge requested by the MergePolicy

 final synchronized int getNumBufferedDeleteTerms() 
{
    return docWriter.getNumBufferedDeleteTerms();
}

 final synchronized int getNumBufferedDocuments() 
{
    return docWriter.getNumDocsInRAM();
}

 public double getRAMBufferSizeMB() 
{
    return docWriter.getRAMBufferSizeMB();
}

Returns the value set by #setRAMBufferSizeMB if enabled.

 final synchronized int getSegmentCount() 
{
    return segmentInfos.size();
}

 public Similarity getSimilarity() 
{
    ensureOpen();
    return this.similarity;
}

Expert: Return the Similarity implementation used by this IndexWriter.

This defaults to the current value of Similarity#getDefault() .

 public int getTermIndexInterval() 
{
    ensureOpen();
    return termIndexInterval;
}

Expert: Return the interval between indexed terms.

 public boolean getUseCompoundFile() 
{
    return getLogMergePolicy().getUseCompoundFile();
}

Get the current setting of whether newly flushed segments will use the compound file format. Note that this just returns the value previously set with setUseCompoundFile(boolean), or the default value (true). You cannot use this to query the status of previously flushed segments.

Note that this method is a convenience method: it just calls mergePolicy.getUseCompoundFile as long as mergePolicy is an instance of LogMergePolicy . Otherwise an IllegalArgumentException is thrown.

 public long getWriteLockTimeout() 
{
    ensureOpen();
    return writeLockTimeout;
}

Returns allowed timeout when acquiring the write lock.

 public final  void maybeMerge() throws IOException, CorruptIndexException 
{
    maybeMerge(false);
}

Expert: asks the mergePolicy whether any merges are necessary now and if so, runs the requested merges and then iterate (test again if merges are needed) until no more merges are returned by the mergePolicy. Explicit calls to maybeMerge() are usually not necessary. The most common case is when merge policy parameters have changed.

 final  void merge(MergePolicy.OneMerge merge) throws IOException, CorruptIndexException 
{
    assert merge.registerDone;
    assert !merge.optimize || merge.maxNumSegmentsOptimize  > 0;
    boolean success = false;
    try {
      try {
        try {
          mergeInit(merge);
          if (infoStream != null)
            message("now merge\n  merge=" + merge.segString(directory) + "\n  index=" + segString());
          mergeMiddle(merge);
          success = true;
        } catch (MergePolicy.MergeAbortedException e) {
          merge.setException(e);
          addMergeException(merge);
          // We can ignore this exception, unless the merge
          // involves segments from external directories, in
          // which case we must throw it so, for example, the
          // rollbackTransaction code in addIndexes* is
          // executed.
          if (merge.isExternal)
            throw e;
        }
      } finally {
        synchronized(this) {
          try {
            mergeFinish(merge);
            if (!success) {
              if (infoStream != null)
                message("hit exception during merge");
              addMergeException(merge);
              if (merge.info != null && !segmentInfos.contains(merge.info))
                deleter.refresh(merge.info.name);
            }
            // This merge (and, generally, any change to the
            // segments) may now enable new merges, so we call
            // merge policy & update pending merges.
            if (success && !merge.isAborted() && !closed && !closing)
              updatePendingMerges(merge.maxNumSegmentsOptimize, merge.optimize);
          } finally {
            runningMerges.remove(merge);
            // Optimize may be waiting on the final optimize
            // merge to finish; and finishMerges() may be
            // waiting for all merges to finish:
            notifyAll();
          }
        }
      }
    } catch (OutOfMemoryError oom) {
      hitOOM = true;
      throw oom;
    }
}

Merges the indicated segments, replacing them in the stack with a single segment.

 final synchronized  void mergeFinish(MergePolicy.OneMerge merge) throws IOException 
{
    if (merge.increfDone)
      decrefMergeSegments(merge);
    assert merge.registerDone;
    final SegmentInfos sourceSegments = merge.segments;
    final int end = sourceSegments.size();
    for(int i=0;i< end;i++)
      mergingSegments.remove(sourceSegments.info(i));
    mergingSegments.remove(merge.info);
    merge.registerDone = false;
}

Does fininishing for a merge, which is fast but holds the synchronized lock on IndexWriter instance.

 final synchronized  void mergeInit(MergePolicy.OneMerge merge) throws IOException 
{
    boolean success = false;
    try {
      _mergeInit(merge);
      success = true;
    } finally {
      if (!success) {
        mergeFinish(merge);
        runningMerges.remove(merge);
      }
    }
}

Does initial setup for a merge, which is fast but holds the synchronized lock on IndexWriter instance.

 public  void message(String message) 
{
    if (infoStream != null)
      infoStream.println("IW " + messageID + " [" + Thread.currentThread().getName() + "]: " + message);
}

Prints a message to the infoStream (if non-null), prefixed with the identifying information for this writer and the thread that's calling it.

 final String newSegmentName() 
{
    // Cannot synchronize on IndexWriter because that causes
    // deadlock
    synchronized(segmentInfos) {
      // Important to set commitPending so that the
      // segmentInfos is written on close.  Otherwise we
      // could close, re-open and re-return the same segment
      // name that was previously returned which can cause
      // problems at least with ConcurrentMergeScheduler.
      commitPending = true;
      return "_" + Integer.toString(segmentInfos.counter++, Character.MAX_RADIX);
    }
}

 SegmentInfo newestSegment() 
{
    return segmentInfos.info(segmentInfos.size()-1);
}

 public final synchronized int numRamDocs() 
{
    ensureOpen();
    return docWriter.getNumDocsInRAM();
}

Expert: Return the number of documents whose segments are currently cached in memory. Useful when calling flush()

 public  void optimize() throws IOException, CorruptIndexException 
{
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
    optimize(true);
}

Requests an "optimize" operation on an index, priming the index for the fastest available search. Traditionally this has meant merging all segments into a single segment as is done in the default merge policy, but individaul merge policies may implement optimize in different ways.

 public  void optimize(int maxNumSegments) throws IOException, CorruptIndexException 
{
    optimize(maxNumSegments, true);
}

Optimize the index down to <= maxNumSegments. If maxNumSegments==1 then this is the same as #optimize() .

 public  void optimize(boolean doWait) throws IOException, CorruptIndexException 
{
    optimize(1, doWait);
}

Just like #optimize() , except you can specify whether the call should block until the optimize completes. This is only meaningful with a MergeScheduler that is able to run merges in background threads.

 public  void optimize(int maxNumSegments,
    boolean doWait) throws IOException, CorruptIndexException 
{
    ensureOpen();
    if (maxNumSegments <  1)
      throw new IllegalArgumentException("maxNumSegments must be  >= 1; got " + maxNumSegments);
    if (infoStream != null)
      message("optimize: index now " + segString());
    flush();
    synchronized(this) {
      resetMergeExceptions();
      segmentsToOptimize = new HashSet();
      final int numSegments = segmentInfos.size();
      for(int i=0;i< numSegments;i++)
        segmentsToOptimize.add(segmentInfos.info(i));
      // Now mark all pending & running merges as optimize
      // merge:
      Iterator it = pendingMerges.iterator();
      while(it.hasNext()) {
        final MergePolicy.OneMerge merge = (MergePolicy.OneMerge) it.next();
        merge.optimize = true;
        merge.maxNumSegmentsOptimize = maxNumSegments;
      }
      it = runningMerges.iterator();
      while(it.hasNext()) {
        final MergePolicy.OneMerge merge = (MergePolicy.OneMerge) it.next();
        merge.optimize = true;
        merge.maxNumSegmentsOptimize = maxNumSegments;
      }
    }
    maybeMerge(maxNumSegments, true);
    if (doWait) {
      synchronized(this) {
        while(optimizeMergesPending()) {
          try {
            wait();
          } catch (InterruptedException ie) {
          }
          if (mergeExceptions.size()  > 0) {
            // Forward any exceptions in background merge
            // threads to the current thread:
            final int size = mergeExceptions.size();
            for(int i=0;i< size;i++) {
              final MergePolicy.OneMerge merge = (MergePolicy.OneMerge) mergeExceptions.get(0);
              if (merge.optimize) {
                IOException err = new IOException("background merge hit exception: " + merge.segString(directory));
                err.initCause(merge.getException());
                throw err;
              }
            }
          }
        }
      }
    }
    // NOTE: in the ConcurrentMergeScheduler case, when
    // doWait is false, we can return immediately while
    // background threads accomplish the optimization
}

Just like #optimize(int) , except you can specify whether the call should block until the optimize completes. This is only meaningful with a MergeScheduler that is able to run merges in background threads.

 public final long ramSizeInBytes() 
{
    ensureOpen();
    return docWriter.getRAMUsed();
}

Expert: Return the total size of all index files currently cached in memory. Useful for size management with flushRamDocs()

 final synchronized boolean registerMerge(MergePolicy.OneMerge merge) 
{
    if (merge.registerDone)
      return true;
    final int count = merge.segments.size();
    boolean isExternal = false;
    for(int i=0;i< count;i++) {
      final SegmentInfo info = merge.segments.info(i);
      if (mergingSegments.contains(info))
        return false;
      if (segmentInfos.indexOf(info) == -1)
        return false;
      if (info.dir != directory)
        isExternal = true;
    }
    pendingMerges.add(merge);
    if (infoStream != null)
      message("add merge to pendingMerges: " + merge.segString(directory) + " [total " + pendingMerges.size() + " pending]");
    merge.mergeGen = mergeGen;
    merge.isExternal = isExternal;
    // OK it does not conflict; now record that this merge
    // is running (while synchronized) to avoid race
    // condition where two conflicting merges from different
    // threads, start
    for(int i=0;i< count;i++)
      mergingSegments.add(merge.segments.info(i));
    // Merge is now registered
    merge.registerDone = true;
    return true;
}

Checks whether this merge involves any segments already participating in a merge. If not, this merge is "registered", meaning we record that its segments are now participating in a merge, and true is returned. Else (the merge conflicts) false is returned.

 public synchronized String segString() 
{
    StringBuffer buffer = new StringBuffer();
    for(int i = 0; i <  segmentInfos.size(); i++) {
      if (i  > 0) {
        buffer.append(' ");
      }
      buffer.append(segmentInfos.info(i).segString(directory));
    }
    return buffer.toString();
}

 public static  void setDefaultInfoStream(PrintStream infoStream) 
{
    IndexWriter.defaultInfoStream = infoStream;
}

If non-null, this will be the default infoStream used by a newly instantiated IndexWriter.

 public static  void setDefaultWriteLockTimeout(long writeLockTimeout) 
{
    IndexWriter.WRITE_LOCK_TIMEOUT = writeLockTimeout;
}

Sets the default (for any instance of IndexWriter) maximum time to wait for a write lock (in milliseconds).

 public  void setInfoStream(PrintStream infoStream) 
{
    ensureOpen();
    this.infoStream = infoStream;
    setMessageID();
    docWriter.setInfoStream(infoStream);
    deleter.setInfoStream(infoStream);
    if (infoStream != null)
      messageState();
}

If non-null, information about merges, deletes and a message when maxFieldLength is reached will be printed to this.

 public  void setMaxBufferedDeleteTerms(int maxBufferedDeleteTerms) 
{
    ensureOpen();
    if (maxBufferedDeleteTerms != DISABLE_AUTO_FLUSH
        && maxBufferedDeleteTerms <  1)
      throw new IllegalArgumentException(
          "maxBufferedDeleteTerms must at least be 1 when enabled");
    docWriter.setMaxBufferedDeleteTerms(maxBufferedDeleteTerms);
    if (infoStream != null)
      message("setMaxBufferedDeleteTerms " + maxBufferedDeleteTerms);
}

Determines the minimal number of delete terms required before the buffered in-memory delete terms are applied and flushed. If there are documents buffered in memory at the time, they are merged and a new segment is created.

Disabled by default (writer flushes by RAM usage).

 public  void setMaxBufferedDocs(int maxBufferedDocs) 
{
    ensureOpen();
    if (maxBufferedDocs != DISABLE_AUTO_FLUSH && maxBufferedDocs <  2)
      throw new IllegalArgumentException(
          "maxBufferedDocs must at least be 2 when enabled");
    if (maxBufferedDocs == DISABLE_AUTO_FLUSH
        && getRAMBufferSizeMB() == DISABLE_AUTO_FLUSH)
      throw new IllegalArgumentException(
          "at least one of ramBufferSize and maxBufferedDocs must be enabled");
    docWriter.setMaxBufferedDocs(maxBufferedDocs);
    pushMaxBufferedDocs();
    if (infoStream != null)
      message("setMaxBufferedDocs " + maxBufferedDocs);
}

Determines the minimal number of documents required before the buffered in-memory documents are flushed as a new Segment. Large values generally gives faster indexing.

When this is set, the writer will flush every maxBufferedDocs added documents. Pass in #DISABLE_AUTO_FLUSH to prevent triggering a flush due to number of buffered documents. Note that if flushing by RAM usage is also enabled, then the flush will be triggered by whichever comes first.

Disabled by default (writer flushes by RAM usage).

 public  void setMaxFieldLength(int maxFieldLength) 
{
    ensureOpen();
    this.maxFieldLength = maxFieldLength;
    if (infoStream != null)
      message("setMaxFieldLength " + 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. This setting refers to the number of running terms, not to the number of different terms.

Note: this silently truncates large documents, excluding from the index all 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  void setMaxMergeDocs(int maxMergeDocs) 
{
    getLogMergePolicy().setMaxMergeDocs(maxMergeDocs);
}

Determines the largest segment (measured by document count) that may be merged with other segments. 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 Integer#MAX_VALUE .

Note that this method is a convenience method: it just calls mergePolicy.setMaxMergeDocs as long as mergePolicy is an instance of LogMergePolicy . Otherwise an IllegalArgumentException is thrown.

The default merge policy (LogByteSizeMergePolicy ) also allows you to set this limit by net size (in MB) of the segment, using LogByteSizeMergePolicy#setMaxMergeMB .

 public  void setMergeFactor(int mergeFactor) 
{
    getLogMergePolicy().setMergeFactor(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.

Note that this method is a convenience method: it just calls mergePolicy.setMergeFactor as long as mergePolicy is an instance of LogMergePolicy . Otherwise an IllegalArgumentException is thrown.

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

 public  void setMergePolicy(MergePolicy mp) 
{
    ensureOpen();
    if (mp == null)
      throw new NullPointerException("MergePolicy must be non-null");
    if (mergePolicy != mp)
      mergePolicy.close();
    mergePolicy = mp;
    pushMaxBufferedDocs();
    if (infoStream != null)
      message("setMergePolicy " + mp);
}

Expert: set the merge policy used by this writer.

 public  void setMergeScheduler(MergeScheduler mergeScheduler) throws IOException, CorruptIndexException 
{
    ensureOpen();
    if (mergeScheduler == null)
      throw new NullPointerException("MergeScheduler must be non-null");
    if (this.mergeScheduler != mergeScheduler) {
      finishMerges(true);
      this.mergeScheduler.close();
    }
    this.mergeScheduler = mergeScheduler;
    if (infoStream != null)
      message("setMergeScheduler " + mergeScheduler);
}

Expert: set the merge scheduler used by this writer.

 public  void setRAMBufferSizeMB(double mb) 
{
    if (mb != DISABLE_AUTO_FLUSH && mb < = 0.0)
      throw new IllegalArgumentException(
          "ramBufferSize should be  > 0.0 MB when enabled");
    if (mb == DISABLE_AUTO_FLUSH && getMaxBufferedDocs() == DISABLE_AUTO_FLUSH)
      throw new IllegalArgumentException(
          "at least one of ramBufferSize and maxBufferedDocs must be enabled");
    docWriter.setRAMBufferSizeMB(mb);
    if (infoStream != null)
      message("setRAMBufferSizeMB " + mb);
}

Determines the amount of RAM that may be used for buffering added documents before they are flushed as a new Segment. Generally for faster indexing performance it's best to flush by RAM usage instead of document count and use as large a RAM buffer as you can.

When this is set, the writer will flush whenever buffered documents use this much RAM. Pass in #DISABLE_AUTO_FLUSH to prevent triggering a flush due to RAM usage. Note that if flushing by document count is also enabled, then the flush will be triggered by whichever comes first.

The default value is #DEFAULT_RAM_BUFFER_SIZE_MB .

 public  void setSimilarity(Similarity similarity) 
{
    ensureOpen();
    this.similarity = similarity;
}

Expert: Set the Similarity implementation used by this IndexWriter.

 public  void setTermIndexInterval(int interval) 
{
    ensureOpen();
    this.termIndexInterval = 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.

 public  void setUseCompoundFile(boolean value) 
{
    getLogMergePolicy().setUseCompoundFile(value);
    getLogMergePolicy().setUseCompoundDocStore(value);
}

Setting to turn on usage of a compound file. When on, multiple files for each segment are merged into a single file when a new segment is flushed.

Note that this method is a convenience method: it just calls mergePolicy.setUseCompoundFile as long as mergePolicy is an instance of LogMergePolicy . Otherwise an IllegalArgumentException is thrown.

 public  void setWriteLockTimeout(long writeLockTimeout) 
{
    ensureOpen();
    this.writeLockTimeout = writeLockTimeout;
}

Sets the maximum time to wait for a write lock (in milliseconds) for this instance of IndexWriter. @see

 boolean testPoint(String name) 
{
    return true;
}

 public  void updateDocument(Term term,
    Document doc) throws IOException, CorruptIndexException 
{
    ensureOpen();
    updateDocument(term, doc, getAnalyzer());
}

Updates a document by first deleting the document(s) containing term and then adding the new document. The delete and then add are atomic as seen by a reader on the same index (flush may happen only after the add).

 public  void updateDocument(Term term,
    Document doc,
    Analyzer analyzer) throws IOException, CorruptIndexException 
{
    ensureOpen();
    try {
      boolean doFlush = false;
      boolean success = false;
      try {
        doFlush = docWriter.updateDocument(term, doc, analyzer);
        success = true;
      } finally {
        if (!success) {
          if (infoStream != null)
            message("hit exception updating document");
          synchronized (this) {
            // If docWriter has some aborted files that were
            // never incref'd, then we clean them up here
            final List files = docWriter.abortedFiles();
            if (files != null)
              deleter.deleteNewFiles(files);
          }
        }
      }
      if (doFlush)
        flush(true, false);
    } catch (OutOfMemoryError oom) {
      hitOOM = true;
      throw oom;
    }
}

Updates a document by first deleting the document(s) containing term and then adding the new document. The delete and then add are atomic as seen by a reader on the same index (flush may happen only after the add).