org.apache.lucene.index

Class 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 Also:
IndexModifier supports the important methods of IndexWriter plus deletion

Field Summary

static String
COMMIT_LOCK_NAME
static long
COMMIT_LOCK_TIMEOUT
Default value is 10,000.
static int
DEFAULT_MAX_BUFFERED_DOCS
Default value is 10.
static int
DEFAULT_MAX_FIELD_LENGTH
Default value is 10,000.
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
Deprecated. use DEFAULT_MAX_BUFFERED_DOCS instead
static int
DEFAULT_TERM_INDEX_INTERVAL
Default value is 128.
static String
WRITE_LOCK_NAME
static long
WRITE_LOCK_TIMEOUT
Default value is 1,000.
PrintStream
infoStream
Deprecated. use setInfoStream(PrintStream) instead
int
maxFieldLength
Deprecated. use setMaxFieldLength(int) instead
int
maxMergeDocs
Deprecated. use setMaxMergeDocs(int) instead
int
mergeFactor
Deprecated. use setMergeFactor(int) instead
int
minMergeDocs
Deprecated. use setMaxBufferedDocs(int) instead

Constructor Summary

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

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(IndexReader[] readers)
Merges the provided indexes into this index.
void
addIndexes(Directory[] dirs)
Merges all segments from an array of 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.
Directory
getDirectory()
Returns the Directory used by this index.
PrintStream
getInfoStream()
int
getMaxBufferedDocs()
int
getMaxFieldLength()
int
getMaxMergeDocs()
int
getMergeFactor()
Similarity
getSimilarity()
Expert: Return the Similarity implementation used by this IndexWriter.
int
getTermIndexInterval()
Expert: Return the interval between indexed terms.
boolean
getUseCompoundFile()
Get the current setting of whether to use the compound file format.
void
optimize()
Merges all segments together into a single segment, optimizing an index for search.
void
setInfoStream(PrintStream infoStream)
If non-null, information about merges and a message when maxFieldLength is reached will be printed to this.
void
setMaxBufferedDocs(int maxBufferedDocs)
Determines the minimal number of documents required before the buffered in-memory documents are merging and a new Segment is created.
void
setMaxFieldLength(int maxFieldLength)
The maximum number of terms that will be indexed for a single field in a document.
void
setMaxMergeDocs(int maxMergeDocs)
Determines the largest number of documents ever merged by addDocument().
void
setMergeFactor(int mergeFactor)
Determines how often segment indices are merged by addDocument().
void
setSimilarity(Similarity similarity)
Expert: Set the Similarity implementation used by this IndexWriter.
void
setTermIndexInterval(int interval)
Expert: Set the interval between indexed terms.
void
setUseCompoundFile(boolean value)
Setting to turn on usage of a compound file.

Field Details

COMMIT_LOCK_NAME

public static final String COMMIT_LOCK_NAME

COMMIT_LOCK_TIMEOUT

public static final long COMMIT_LOCK_TIMEOUT
Default value is 10,000.
Field Value:
10000L

DEFAULT_MAX_BUFFERED_DOCS

public static final int DEFAULT_MAX_BUFFERED_DOCS
Field Value:
10

DEFAULT_MAX_FIELD_LENGTH

public static final int DEFAULT_MAX_FIELD_LENGTH
Field Value:
10000

DEFAULT_MAX_MERGE_DOCS

public static final int DEFAULT_MAX_MERGE_DOCS

DEFAULT_MERGE_FACTOR

public static final int DEFAULT_MERGE_FACTOR
Field Value:
10

DEFAULT_MIN_MERGE_DOCS

public static final int DEFAULT_MIN_MERGE_DOCS

Deprecated. use DEFAULT_MAX_BUFFERED_DOCS instead

Field Value:
10

DEFAULT_TERM_INDEX_INTERVAL

public static final int DEFAULT_TERM_INDEX_INTERVAL
Field Value:
128

WRITE_LOCK_NAME

public static final String WRITE_LOCK_NAME

WRITE_LOCK_TIMEOUT

public static final long WRITE_LOCK_TIMEOUT
Default value is 1,000.
Field Value:
1000L

infoStream

public PrintStream infoStream

Deprecated. use setInfoStream(PrintStream) instead

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

maxFieldLength

public int maxFieldLength

Deprecated. use setMaxFieldLength(int) instead

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.


maxMergeDocs

public int maxMergeDocs

Deprecated. use setMaxMergeDocs(int) instead

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.


mergeFactor

public int mergeFactor

Deprecated. use setMergeFactor(int) instead

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 (<3210) for indices that are interactively maintained.

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


minMergeDocs

public int minMergeDocs

Deprecated. use setMaxBufferedDocs(int) instead

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.

Constructor Details

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

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

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

Method Details

addDocument

public void addDocument(Document doc)
            throws IOException
Adds a document to this index. If the document contains more than setMaxFieldLength(int) terms for a given field, the remainder are discarded.

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 setMaxFieldLength(int) terms for a given field, the remainder are discarded.

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.


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.


close

public void close()
            throws IOException
Flushes all changes to an index and closes all associated files.

docCount

public int docCount()
Returns the number of documents currently in this index.

finalize

protected void finalize()
            throws IOException
Release the write lock, if needed.

getAnalyzer

public Analyzer getAnalyzer()
Returns the analyzer used by this index.

getDirectory

public Directory getDirectory()
Returns the Directory used by this index.

getInfoStream

public PrintStream getInfoStream()

getMaxBufferedDocs

public int getMaxBufferedDocs()

getMaxFieldLength

public int getMaxFieldLength()

getMaxMergeDocs

public int getMaxMergeDocs()

getMergeFactor

public int getMergeFactor()

getSimilarity

public Similarity getSimilarity()
Expert: Return the Similarity implementation used by this IndexWriter.

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


getTermIndexInterval

public int getTermIndexInterval()
Expert: Return the interval between indexed terms.

getUseCompoundFile

public boolean getUseCompoundFile()
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.

optimize

public void optimize()
            throws IOException
Merges all segments together into a single segment, optimizing an index for search.

setInfoStream

public void setInfoStream(PrintStream infoStream)
If non-null, information about merges and a message when maxFieldLength is reached will be printed to this.

setMaxBufferedDocs

public void setMaxBufferedDocs(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 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.


setMaxFieldLength

public void setMaxFieldLength(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.


setMaxMergeDocs

public void setMaxMergeDocs(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.


setMergeFactor

public void setMergeFactor(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 (<3210) for indices that are interactively maintained.

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


setSimilarity

public void setSimilarity(Similarity similarity)
Expert: Set the Similarity implementation used by this IndexWriter.

setTermIndexInterval

public void setTermIndexInterval(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.

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.

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