File	Doc	Category	Size	Date	Package
IndexReader.java	API Doc	Apache Lucene 2.2.0	38724	Sat Jun 16 22:20:36 BST 2007	org.apache.lucene.index

IndexReader

• java.lang.Object

Fields Summary
private Directory	directory
private boolean	directoryOwner
private boolean	closeDirectory
private IndexDeletionPolicy	deletionPolicy
private boolean	closed
private SegmentInfos	segmentInfos
private Lock	writeLock
private boolean	stale
private boolean	hasChanges
private boolean	rollbackHasChanges Used by commit() to record pre-commit state in case rollback is necessary
private SegmentInfos	rollbackSegmentInfos

Constructors Summary
protected IndexReader(Directory directory) Constructor used if IndexReader is not owner of its directory. This is used for IndexReaders that are used within other IndexReaders that take care or locking directories. param directory Directory where IndexReader files reside. this.directory = directory;
IndexReader(Directory directory, SegmentInfos segmentInfos, boolean closeDirectory) Constructor used if IndexReader is owner of its directory. If IndexReader is owner of its directory, it locks its directory in case of write operations. param directory Directory where IndexReader files reside. param segmentInfos Used for write-l param closeDirectory init(directory, segmentInfos, closeDirectory, true);

Methods Summary
private void	acquireWriteLock() Tries to acquire the WriteLock on this directory. this method is only valid if this IndexReader is directory owner. throws StaleReaderException if the index has changed since this reader was opened throws CorruptIndexException if the index is corrupt throws LockObtainFailedException if another writer has this index open (write.lock could not be obtained) throws IOException if there is a low-level IO error ensureOpen(); if (stale) throw new StaleReaderException("IndexReader out of date and no longer valid for delete, undelete, or setNorm operations"); if (writeLock == null) { Lock writeLock = directory.makeLock(IndexWriter.WRITE_LOCK_NAME); if (!writeLock.obtain(IndexWriter.WRITE_LOCK_TIMEOUT)) // obtain write lock throw new LockObtainFailedException("Index locked for write: " + writeLock); this.writeLock = writeLock; // we have to check whether index has changed since this reader was opened. // if so, this reader is no longer valid for deletion if (SegmentInfos.readCurrentVersion(directory) > segmentInfos.getVersion()) { stale = true; this.writeLock.release(); this.writeLock = null; throw new StaleReaderException("IndexReader out of date and no longer valid for delete, undelete, or setNorm operations"); } }
public final synchronized void	close() Closes files associated with this index. Also saves any new deletions to disk. No other methods should be called after this has been called. throws IOException if there is a low-level IO error if (!closed) { commit(); doClose(); if (directoryOwner) closed = true; if(closeDirectory) directory.close(); }
protected final synchronized void	commit() Commit changes resulting from delete, undeleteAll, or setNorm operations If an exception is hit, then either no changes or all changes will have been committed to the index (transactional semantics). throws IOException if there is a low-level IO error if(hasChanges){ if(directoryOwner){ // Default deleter (for backwards compatibility) is // KeepOnlyLastCommitDeleter: IndexFileDeleter deleter = new IndexFileDeleter(directory, deletionPolicy == null ? new KeepOnlyLastCommitDeletionPolicy() : deletionPolicy, segmentInfos, null); // Checkpoint the state we are about to change, in // case we have to roll back: startCommit(); boolean success = false; try { doCommit(); segmentInfos.write(directory); success = true; } finally { if (!success) { // Rollback changes that were made to // SegmentInfos but failed to get [fully] // committed. This way this reader instance // remains consistent (matched to what's // actually in the index): rollbackCommit(); // Recompute deletable files & remove them (so // partially written .del files, etc, are // removed): deleter.refresh(); } } // Have the deleter remove any now unreferenced // files due to this commit: deleter.checkpoint(segmentInfos, true); if (writeLock != null) { writeLock.release(); // release write lock writeLock = null; } } else doCommit(); } hasChanges = false;
public final synchronized void	deleteDocument(int docNum) Deletes the document numbered docNum. Once a document is deleted it will not appear in TermDocs or TermPostitions enumerations. Attempts to read its field with the {@link #document} method will result in an error. The presence of this document may still be reflected in the {@link #docFreq} statistic, though this will be corrected eventually as the index is further modified. throws StaleReaderException if the index has changed since this reader was opened throws CorruptIndexException if the index is corrupt throws LockObtainFailedException if another writer has this index open (write.lock could not be obtained) throws IOException if there is a low-level IO error ensureOpen(); if(directoryOwner) acquireWriteLock(); hasChanges = true; doDelete(docNum);
public final int	deleteDocuments(org.apache.lucene.index.Term term) Deletes all documents that have a given term indexed. This is useful if one uses a document field to hold a unique ID string for the document. Then to delete such a document, one merely constructs a term with the appropriate field and the unique ID string as its text and passes it to this method. See {@link #deleteDocument(int)} for information about when this deletion will become effective. return the number of documents deleted throws StaleReaderException if the index has changed since this reader was opened throws CorruptIndexException if the index is corrupt throws LockObtainFailedException if another writer has this index open (write.lock could not be obtained) throws IOException if there is a low-level IO error ensureOpen(); TermDocs docs = termDocs(term); if (docs == null) return 0; int n = 0; try { while (docs.next()) { deleteDocument(docs.doc()); n++; } } finally { docs.close(); } return n;
public org.apache.lucene.store.Directory	directory() Returns the directory this index resides in. ensureOpen(); return directory;
protected abstract void	doClose() Implements close.
protected abstract void	doCommit() Implements commit.
protected abstract void	doDelete(int docNum) Implements deletion of the document numbered docNum. Applications should call {@link #deleteDocument(int)} or {@link #deleteDocuments(Term)}.
protected abstract void	doSetNorm(int doc, java.lang.String field, byte value) Implements setNorm in subclass.
protected abstract void	doUndeleteAll() Implements actual undeleteAll() in subclass.
public abstract int	docFreq(org.apache.lucene.index.Term t) Returns the number of documents containing the term t. throws IOException if there is a low-level IO error
public org.apache.lucene.document.Document	document(int n) Returns the stored fields of the nth Document in this index. throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error ensureOpen(); return document(n, null);
public abstract org.apache.lucene.document.Document	document(int n, org.apache.lucene.document.FieldSelector fieldSelector) Get the {@link org.apache.lucene.document.Document} at the nth position. The {@link org.apache.lucene.document.FieldSelector} may be used to determine what {@link org.apache.lucene.document.Field}s to load and how they should be loaded. NOTE: If this Reader (more specifically, the underlying FieldsReader) is closed before the lazy {@link org.apache.lucene.document.Field} is loaded an exception may be thrown. If you want the value of a lazy {@link org.apache.lucene.document.Field} to be available after closing you must explicitly load it or fetch the Document again with a new loader. param n Get the document at the nth position param fieldSelector The {@link org.apache.lucene.document.FieldSelector} to use to determine what Fields should be loaded on the Document. May be null, in which case all Fields will be loaded. return The stored fields of the {@link org.apache.lucene.document.Document} at the nth position throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error see org.apache.lucene.document.Fieldable see org.apache.lucene.document.FieldSelector see org.apache.lucene.document.SetBasedFieldSelector see org.apache.lucene.document.LoadFirstFieldSelector
protected final void	ensureOpen() throws AlreadyClosedException if this IndexReader is closed if (closed) { throw new AlreadyClosedException("this IndexReader is closed"); }
protected void	finalize() Release the write lock, if needed. try { if (writeLock != null) { writeLock.release(); // release write lock writeLock = null; } } finally { super.finalize(); }
public static long	getCurrentVersion(java.lang.String directory) Reads version number from segments files. The version number is initialized with a timestamp and then increased by one for each change of the index. param directory where the index resides. return version number. throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error return getCurrentVersion(new File(directory));
public static long	getCurrentVersion(java.io.File directory) Reads version number from segments files. The version number is initialized with a timestamp and then increased by one for each change of the index. param directory where the index resides. return version number. throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error Directory dir = FSDirectory.getDirectory(directory); long version = getCurrentVersion(dir); dir.close(); return version;
public static long	getCurrentVersion(org.apache.lucene.store.Directory directory) Reads version number from segments files. The version number is initialized with a timestamp and then increased by one for each change of the index. param directory where the index resides. return version number. throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error return SegmentInfos.readCurrentVersion(directory);
public abstract java.util.Collection	getFieldNames(org.apache.lucene.index.IndexReader$FieldOption fldOption) Get a list of unique field names that exist in this index and have the specified field option information. param fldOption specifies which field option should be available for the returned fields return Collection of Strings indicating the names of the fields. see IndexReader.FieldOption
public abstract org.apache.lucene.index.TermFreqVector	getTermFreqVector(int docNumber, java.lang.String field) Return a term frequency vector for the specified document and field. The returned vector contains terms and frequencies for the terms in the specified field of this document, if the field had the storeTermVector flag set. If termvectors had been stored with positions or offsets, a TermPositionsVector is returned. param docNumber document for which the term frequency vector is returned param field field for which the term frequency vector is returned. return term frequency vector May be null if field does not exist in the specified document or term vector was not stored. throws IOException if index cannot be accessed see org.apache.lucene.document.Field.TermVector
public abstract org.apache.lucene.index.TermFreqVector[]	getTermFreqVectors(int docNumber) Return an array of term frequency vectors for the specified document. The array contains a vector for each vectorized field in the document. Each vector contains terms and frequencies for all terms in a given vectorized field. If no such fields existed, the method returns null. The term vectors that are returned my either be of type TermFreqVector or of type TermPositionsVector if positions or offsets have been stored. param docNumber document for which term frequency vectors are returned return array of term frequency vectors. May be null if no term vectors have been stored for the specified document. throws IOException if index cannot be accessed see org.apache.lucene.document.Field.TermVector
public long	getVersion() Version number when this IndexReader was opened. ensureOpen(); return segmentInfos.getVersion();
public abstract boolean	hasDeletions() Returns true if any documents have been deleted
public boolean	hasNorms(java.lang.String field) Returns true if there are norms stored for this field. // backward compatible implementation. // SegmentReader has an efficient implementation. ensureOpen(); return norms(field) != null;
public static boolean	indexExists(java.lang.String directory) Returns true if an index exists at the specified directory. If the directory does not exist or if there is no index in it. false is returned. param directory the directory to check for an index return true if an index exists; false otherwise return indexExists(new File(directory));
public static boolean	indexExists(java.io.File directory) Returns true if an index exists at the specified directory. If the directory does not exist or if there is no index in it. param directory the directory to check for an index return true if an index exists; false otherwise return SegmentInfos.getCurrentSegmentGeneration(directory.list()) != -1;
public static boolean	indexExists(org.apache.lucene.store.Directory directory) Returns true if an index exists at the specified directory. If the directory does not exist or if there is no index in it. param directory the directory to check for an index return true if an index exists; false otherwise throws IOException if there is a problem with accessing the index return SegmentInfos.getCurrentSegmentGeneration(directory) != -1;
void	init(org.apache.lucene.store.Directory directory, org.apache.lucene.index.SegmentInfos segmentInfos, boolean closeDirectory, boolean directoryOwner) this.directory = directory; this.segmentInfos = segmentInfos; this.directoryOwner = directoryOwner; this.closeDirectory = closeDirectory;
public boolean	isCurrent() Check whether this IndexReader is still using the current (i.e., most recently committed) version of the index. If a writer has committed any changes to the index since this reader was opened, this will return false, in which case you must open a new IndexReader in order to see the changes. See the description of the autoCommit flag which controls when the {@link IndexWriter} actually commits changes to the index. throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error ensureOpen(); return SegmentInfos.readCurrentVersion(directory) == segmentInfos.getVersion();
public abstract boolean	isDeleted(int n) Returns true if document n has been deleted
public static boolean	isLocked(org.apache.lucene.store.Directory directory) Returns true iff the index in the named directory is currently locked. param directory the directory to check for a lock throws IOException if there is a low-level IO error return directory.makeLock(IndexWriter.WRITE_LOCK_NAME).isLocked();
public static boolean	isLocked(java.lang.String directory) Returns true iff the index in the named directory is currently locked. param directory the directory to check for a lock throws IOException if there is a low-level IO error Directory dir = FSDirectory.getDirectory(directory); boolean result = isLocked(dir); dir.close(); return result;
public boolean	isOptimized() Checks is the index is optimized (if it has a single segment and no deletions) return true if the index is optimized; false otherwise ensureOpen(); return segmentInfos.size() == 1 && hasDeletions() == false;
public static long	lastModified(java.lang.String directory) Returns the time the index in the named directory was last modified. Do not use this to check whether the reader is still up-to-date, use {@link #isCurrent()} instead. throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error return lastModified(new File(directory));
public static long	lastModified(java.io.File fileDirectory) Returns the time the index in the named directory was last modified. Do not use this to check whether the reader is still up-to-date, use {@link #isCurrent()} instead. throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error return ((Long) new SegmentInfos.FindSegmentsFile(fileDirectory) { public Object doBody(String segmentFileName) { return new Long(FSDirectory.fileModified(fileDirectory, segmentFileName)); } }.run()).longValue();
public static long	lastModified(org.apache.lucene.store.Directory directory2) Returns the time the index in the named directory was last modified. Do not use this to check whether the reader is still up-to-date, use {@link #isCurrent()} instead. throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error return ((Long) new SegmentInfos.FindSegmentsFile(directory2) { public Object doBody(String segmentFileName) throws IOException { return new Long(directory2.fileModified(segmentFileName)); } }.run()).longValue();
public static void	main(java.lang.String[] args) Prints the filename and size of each file within a given compound file. Add the -extract flag to extract files to the current working directory. In order to make the extracted version of the index work, you have to copy the segments file from the compound index into the directory where the extracted files are stored. param args Usage: org.apache.lucene.index.IndexReader [-extract] <cfsfile> String filename = null; boolean extract = false; for (int i = 0; i < args.length; ++i) { if (args[i].equals("-extract")) { extract = true; } else if (filename == null) { filename = args[i]; } } if (filename == null) { System.out.println("Usage: org.apache.lucene.index.IndexReader [-extract] <cfsfile>"); return; } Directory dir = null; CompoundFileReader cfr = null; try { File file = new File(filename); String dirname = file.getAbsoluteFile().getParent(); filename = file.getName(); dir = FSDirectory.getDirectory(dirname); cfr = new CompoundFileReader(dir, filename); String [] files = cfr.list(); Arrays.sort(files); // sort the array of filename so that the output is more readable for (int i = 0; i < files.length; ++i) { long len = cfr.fileLength(files[i]); if (extract) { System.out.println("extract " + files[i] + " with " + len + " bytes to local directory..."); IndexInput ii = cfr.openInput(files[i]); FileOutputStream f = new FileOutputStream(files[i]); // read and write with a small buffer, which is more effectiv than reading byte by byte byte[] buffer = new byte[1024]; int chunk = buffer.length; while(len > 0) { final int bufLen = (int) Math.min(chunk, len); ii.readBytes(buffer, 0, bufLen); f.write(buffer, 0, bufLen); len -= bufLen; } f.close(); ii.close(); } else System.out.println(files[i] + ": " + len + " bytes"); } } catch (IOException ioe) { ioe.printStackTrace(); } finally { try { if (dir != null) dir.close(); if (cfr != null) cfr.close(); } catch (IOException ioe) { ioe.printStackTrace(); } }
public abstract int	maxDoc() Returns one greater than the largest possible document number. This may be used to, e.g., determine how big to allocate an array which will have an element for every document number in an index.
public abstract byte[]	norms(java.lang.String field) Returns the byte-encoded normalization factor for the named field of every document. This is used by the search code to score documents. see org.apache.lucene.document.Field#setBoost(float)
public abstract void	norms(java.lang.String field, byte[] bytes, int offset) Reads the byte-encoded normalization factor for the named field of every document. This is used by the search code to score documents. see org.apache.lucene.document.Field#setBoost(float)
public abstract int	numDocs() Returns the number of documents in this index.
public static org.apache.lucene.index.IndexReader	open(java.lang.String path) Returns an IndexReader reading the index in an FSDirectory in the named path. throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error param path the path to the index directory return open(FSDirectory.getDirectory(path), true, null);
public static org.apache.lucene.index.IndexReader	open(java.io.File path) Returns an IndexReader reading the index in an FSDirectory in the named path. param path the path to the index directory throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error return open(FSDirectory.getDirectory(path), true, null);
public static org.apache.lucene.index.IndexReader	open(org.apache.lucene.store.Directory directory) Returns an IndexReader reading the index in the given Directory. param directory the index directory throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error return open(directory, false, null);
public static org.apache.lucene.index.IndexReader	open(org.apache.lucene.store.Directory directory, org.apache.lucene.index.IndexDeletionPolicy deletionPolicy) Expert: returns an IndexReader reading the index in the given Directory, with a custom {@link IndexDeletionPolicy}. param directory the index directory param deletionPolicy a custom deletion policy (only used if you use this reader to perform deletes or to set norms); see {@link IndexWriter} for details. throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error return open(directory, false, deletionPolicy);
private static org.apache.lucene.index.IndexReader	open(org.apache.lucene.store.Directory directory, boolean closeDirectory, org.apache.lucene.index.IndexDeletionPolicy deletionPolicy) return (IndexReader) new SegmentInfos.FindSegmentsFile(directory) { protected Object doBody(String segmentFileName) throws CorruptIndexException, IOException { SegmentInfos infos = new SegmentInfos(); infos.read(directory, segmentFileName); IndexReader reader; if (infos.size() == 1) { // index is optimized reader = SegmentReader.get(infos, infos.info(0), closeDirectory); } else { // To reduce the chance of hitting FileNotFound // (and having to retry), we open segments in // reverse because IndexWriter merges & deletes // the newest segments first. IndexReader[] readers = new IndexReader[infos.size()]; for (int i = infos.size()-1; i >= 0; i--) { try { readers[i] = SegmentReader.get(infos.info(i)); } catch (IOException e) { // Close all readers we had opened: for(i++;i<infos.size();i++) { readers[i].close(); } throw e; } } reader = new MultiReader(directory, infos, closeDirectory, readers); } reader.deletionPolicy = deletionPolicy; return reader; } }.run();
void	rollbackCommit() Rolls back state to just before the commit (this is called by commit() if there is some exception while committing). if (directoryOwner) { for(int i=0;i<segmentInfos.size();i++) { // Rollback each segmentInfo. Because the // SegmentReader holds a reference to the // SegmentInfo we can't [easily] just replace // segmentInfos, so we reset it in place instead: segmentInfos.info(i).reset(rollbackSegmentInfos.info(i)); } rollbackSegmentInfos = null; } hasChanges = rollbackHasChanges;
public final synchronized void	setNorm(int doc, java.lang.String field, byte value) Expert: Resets the normalization factor for the named field of the named document. The norm represents the product of the field's {@link org.apache.lucene.document.Fieldable#setBoost(float) boost} and its {@link Similarity#lengthNorm(String, int) length normalization}. Thus, to preserve the length normalization values when resetting this, one should base the new value upon the old. see #norms(String) see Similarity#decodeNorm(byte) throws StaleReaderException if the index has changed since this reader was opened throws CorruptIndexException if the index is corrupt throws LockObtainFailedException if another writer has this index open (write.lock could not be obtained) throws IOException if there is a low-level IO error ensureOpen(); if(directoryOwner) acquireWriteLock(); hasChanges = true; doSetNorm(doc, field, value);
public void	setNorm(int doc, java.lang.String field, float value) Expert: Resets the normalization factor for the named field of the named document. see #norms(String) see Similarity#decodeNorm(byte) throws StaleReaderException if the index has changed since this reader was opened throws CorruptIndexException if the index is corrupt throws LockObtainFailedException if another writer has this index open (write.lock could not be obtained) throws IOException if there is a low-level IO error ensureOpen(); setNorm(doc, field, Similarity.encodeNorm(value));
void	startCommit() Should internally checkpoint state that will change during commit so that we can rollback if necessary. if (directoryOwner) { rollbackSegmentInfos = (SegmentInfos) segmentInfos.clone(); } rollbackHasChanges = hasChanges;
public org.apache.lucene.index.TermDocs	termDocs(org.apache.lucene.index.Term term) Returns an enumeration of all the documents which contain term. For each document, the document number, the frequency of the term in that document is also provided, for use in search scoring. Thus, this method implements the mapping: Term    =>    <docNum, freq>* The enumeration is ordered by document number. Each document number is greater than all that precede it in the enumeration. throws IOException if there is a low-level IO error ensureOpen(); TermDocs termDocs = termDocs(); termDocs.seek(term); return termDocs;
public abstract org.apache.lucene.index.TermDocs	termDocs() Returns an unpositioned {@link TermDocs} enumerator. throws IOException if there is a low-level IO error
public org.apache.lucene.index.TermPositions	termPositions(org.apache.lucene.index.Term term) Returns an enumeration of all the documents which contain term. For each document, in addition to the document number and frequency of the term in that document, a list of all of the ordinal positions of the term in the document is available. Thus, this method implements the mapping: Term    =>    <docNum, freq, <pos1, pos2, ... posfreq-1> >* This positional information faciliates phrase and proximity searching. The enumeration is ordered by document number. Each document number is greater than all that precede it in the enumeration. throws IOException if there is a low-level IO error ensureOpen(); TermPositions termPositions = termPositions(); termPositions.seek(term); return termPositions;
public abstract org.apache.lucene.index.TermPositions	termPositions() Returns an unpositioned {@link TermPositions} enumerator. throws IOException if there is a low-level IO error
public abstract org.apache.lucene.index.TermEnum	terms() Returns an enumeration of all the terms in the index. The enumeration is ordered by Term.compareTo(). Each term is greater than all that precede it in the enumeration. Note that after calling terms(), {@link TermEnum#next()} must be called on the resulting enumeration before calling other methods such as {@link TermEnum#term()}. throws IOException if there is a low-level IO error
public abstract org.apache.lucene.index.TermEnum	terms(org.apache.lucene.index.Term t) Returns an enumeration of all terms starting at a given term. If the given term does not exist, the enumeration is positioned at the first term greater than the supplied therm. The enumeration is ordered by Term.compareTo(). Each term is greater than all that precede it in the enumeration. throws IOException if there is a low-level IO error
public final synchronized void	undeleteAll() Undeletes all documents currently marked as deleted in this index. throws StaleReaderException if the index has changed since this reader was opened throws LockObtainFailedException if another writer has this index open (write.lock could not be obtained) throws CorruptIndexException if the index is corrupt throws IOException if there is a low-level IO error ensureOpen(); if(directoryOwner) acquireWriteLock(); hasChanges = true; doUndeleteAll();
public static void	unlock(org.apache.lucene.store.Directory directory) Forcibly unlocks the index in the named directory. Caution: this should only be used by failure recovery code, when it is known that no other process nor thread is in fact currently accessing this index. directory.makeLock(IndexWriter.WRITE_LOCK_NAME).release();