gate.creole.annic.apache.lucene.index
Class IndexWriter

java.lang.Object
  gate.creole.annic.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.

Field Summary

static String	COMMIT_LOCK_NAME
static long	COMMIT_LOCK_TIMEOUT Default value is 10000.
static int	DEFAULT_MAX_FIELD_LENGTH Default value is 10000.
static int	DEFAULT_MAX_MERGE_DOCS Default value is Integer.MAX_VALUE.
static int	DEFAULT_MERGE_FACTOR Default value is 10.
static int	DEFAULT_MIN_MERGE_DOCS Default value is 10.
PrintStream	infoStream If non-null, information about merges will be printed to this.
int	maxFieldLength The maximum number of terms that will be indexed for a single field in a document.
int	maxMergeDocs Determines the largest number of documents ever merged by addDocument().
int	mergeFactor Determines how often segment indices are merged by addDocument().
int	minMergeDocs Determines the minimal number of documents required before the buffered in-memory documents are merging and a new Segment is created.
static String	WRITE_LOCK_NAME
static long	WRITE_LOCK_TIMEOUT Default value is 1000.

Constructor Summary

IndexWriter(Directory d, Analyzer a, boolean create)
Constructs an IndexWriter for the index in d.

IndexWriter(File path, Analyzer a, boolean create)
Constructs an IndexWriter for the index in path.

IndexWriter(String path, Analyzer a, boolean create)
Constructs an IndexWriter for the index in path.

Method Summary

void	addDocument(Document doc) Adds a document to this index.
void	addDocument(Document doc, Analyzer analyzer) Adds a document to this index, using the provided analyzer instead of the value of getAnalyzer().
void	addIndexes(Directory[] dirs) Merges all segments from an array of indexes into this index.
void	addIndexes(IndexReader[] readers) Merges the provided indexes into this index.
void	close() Flushes all changes to an index and closes all associated files.
int	docCount() Returns the number of documents currently in this index.
protected void	finalize() Release the write lock, if needed.
Analyzer	getAnalyzer() Returns the analyzer used by this index.
Similarity	getSimilarity() Expert: Return the Similarity implementation used by this IndexWriter.
boolean	getUseCompoundFile() Setting to turn on usage of a compound file.
void	optimize() Merges all segments together into a single segment, optimizing an index for search.
void	setSimilarity(Similarity similarity) Expert: Set the Similarity implementation used by this IndexWriter.
void	setUseCompoundFile(boolean value) Setting to turn on usage of a compound file.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

WRITE_LOCK_TIMEOUT

public static final long WRITE_LOCK_TIMEOUT

Default value is 1000. Use gate.creole.annic.apache.lucene.writeLockTimeout system property to override.

COMMIT_LOCK_TIMEOUT

public static final long COMMIT_LOCK_TIMEOUT

Default value is 10000. Use gate.creole.annic.apache.lucene.commitLockTimeout system property to override.

WRITE_LOCK_NAME

public static final String WRITE_LOCK_NAME

See Also:

Constant Field Values

COMMIT_LOCK_NAME

public static final String COMMIT_LOCK_NAME

See Also:

Constant Field Values

DEFAULT_MERGE_FACTOR

public static final int DEFAULT_MERGE_FACTOR

Default value is 10. Use gate.creole.annic.apache.lucene.mergeFactor system property to override.

DEFAULT_MIN_MERGE_DOCS

public static final int DEFAULT_MIN_MERGE_DOCS

Default value is 10. Use gate.creole.annic.apache.lucene.minMergeDocs system property to override.

DEFAULT_MAX_MERGE_DOCS

public static final int DEFAULT_MAX_MERGE_DOCS

Default value is Integer.MAX_VALUE. Use gate.creole.annic.apache.lucene.maxMergeDocs system property to override.

DEFAULT_MAX_FIELD_LENGTH

public static final int DEFAULT_MAX_FIELD_LENGTH

Default value is 10000. Use gate.creole.annic.apache.lucene.maxFieldLength system property to override.

maxFieldLength

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.

mergeFactor

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.

minMergeDocs

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 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.

maxMergeDocs

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 Integer.MAX_VALUE.

infoStream

public PrintStream infoStream

If non-null, information about merges will be printed to this.

Constructor Detail

IndexWriter

public IndexWriter(String path,
                   Analyzer a,
                   boolean create)
            throws IOException

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:

IOException - if the directory cannot be read/written to, or if it does not exist, and create is false

IndexWriter

public IndexWriter(File path,
                   Analyzer a,
                   boolean create)
            throws IOException

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:

IOException - if the directory cannot be read/written to, or if it does not exist, and create is false

IndexWriter

public IndexWriter(Directory d,
                   Analyzer a,
                   boolean create)
            throws IOException

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:

IOException - if the directory cannot be read/written to, or if it does not exist, and create is false

Method Detail

getUseCompoundFile

public boolean getUseCompoundFile()

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.

setUseCompoundFile

public void setUseCompoundFile(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.

setSimilarity

public void setSimilarity(Similarity similarity)

Expert: Set the Similarity implementation used by this IndexWriter.

See Also:

Similarity.setDefault(Similarity)

getSimilarity

public Similarity getSimilarity()

Expert: Return the Similarity implementation used by this IndexWriter.

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

close

public void close()
           throws IOException

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

Throws:

IOException

finalize

protected void finalize()
                 throws IOException

Release the write lock, if needed.

Overrides:

finalize in class Object

Throws:

IOException

getAnalyzer

public Analyzer getAnalyzer()

Returns the analyzer used by this index.

docCount

public int docCount()

Returns the number of documents currently in this index.

addDocument

public void addDocument(Document doc)
                 throws IOException

Adds a document to this index. If the document contains more than maxFieldLength terms for a given field, the remainder are discarded.

Throws:

IOException

addDocument

public void addDocument(Document doc,
                        Analyzer analyzer)
                 throws IOException

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

Throws:

IOException

optimize

public void optimize()
              throws IOException

Merges all segments together into a single segment, optimizing an index for search.

Throws:

IOException

addIndexes

public void addIndexes(Directory[] dirs)
                throws IOException

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.

Throws:

IOException

addIndexes

public void addIndexes(IndexReader[] readers)
                throws IOException

Merges the provided indexes into this index.

After this completes, the index is optimized.

The provided IndexReaders are not closed.

Throws:

IOException