org.apache.lucene.index

Class IndexWriter


public class IndexWriter
extends Object

An IndexWriter creates and maintains an index.

The third argument (create) to the constructor determines whether a new index is created, or whether an existing index is opened for the addition of new documents. Note that you can open an index with create=true even while readers are using the index. The old readers will continue to search the "point in time" snapshot they had opened, and won't see the newly created index until they re-open.

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.

As of 2.1, IndexWriter can now delete documents by Term (see deleteDocuments ) and update (delete then add) documents (see updateDocument). Deletes are buffered until setMaxBufferedDeleteTerms(int) Terms at which point they are flushed to the index. Note that a flush occurs when there are enough buffered deletes or enough added documents, whichever is sooner. When a flush occurs, both pending deletes and added documents are flushed to the index.

Field Summary

static int
DEFAULT_MAX_BUFFERED_DELETE_TERMS
Default value is 1000.
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_TERM_INDEX_INTERVAL
Default value is 128.
static String
WRITE_LOCK_NAME
static long
WRITE_LOCK_TIMEOUT
Default value for the write lock timeout (1,000).

Constructor Summary

IndexWriter(File path, Analyzer a)
Constructs an IndexWriter for the index in path, creating it first if it does not already exist, otherwise appending to the existing index.
IndexWriter(File path, Analyzer a, boolean create)
Constructs an IndexWriter for the index in path.
IndexWriter(String path, Analyzer a)
Constructs an IndexWriter for the index in path, creating it first if it does not already exist, otherwise appending to the existing index.
IndexWriter(String path, Analyzer a, boolean create)
Constructs an IndexWriter for the index in path.
IndexWriter(Directory d, Analyzer a)
Constructs an IndexWriter for the index in d, creating it first if it does not already exist, otherwise appending to the existing index.
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
addIndexesNoOptimize(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.
void
deleteDocuments(Term term)
Deletes the document(s) containing term.
void
deleteDocuments(Term[] terms)
Deletes the document(s) containing any of the terms.
int
docCount()
Returns the number of documents currently in this index.
protected void
finalize()
Release the write lock, if needed.
void
flush()
Flush all in-memory buffered updates (adds and deletes) to the Directory.
Analyzer
getAnalyzer()
Returns the analyzer used by this index.
static long
getDefaultWriteLockTimeout()
Directory
getDirectory()
Returns the Directory used by this index.
PrintStream
getInfoStream()
int
getMaxBufferedDeleteTerms()
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.
long
getWriteLockTimeout()
protected void
maybeFlushRamSegments()
int
numRamDocs()
Expert: Return the number of documents whose segments are currently cached in memory.
void
optimize()
Merges all segments together into a single segment, optimizing an index for search.
long
ramSizeInBytes()
Expert: Return the total size of all index files currently cached in memory.
static void
setDefaultWriteLockTimeout(long writeLockTimeout)
Sets the default (for any instance of IndexWriter) maximum time to wait for a write lock (in milliseconds).
void
setInfoStream(PrintStream infoStream)
If non-null, information about merges and a message when maxFieldLength is reached will be printed to this.
void
setMaxBufferedDeleteTerms(int maxBufferedDeleteTerms)
Determines the minimal number of delete terms required before the buffered in-memory delete terms are applied and flushed.
void
setMaxBufferedDocs(int maxBufferedDocs)
Determines the minimal number of documents required before the buffered in-memory documents are merged 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.
void
setWriteLockTimeout(long writeLockTimeout)
Sets the maximum time to wait for a write lock (in milliseconds) for this instance of IndexWriter.
void
updateDocument(Term term, Document doc)
Updates a document by first deleting the document(s) containing term and then adding the new document.
void
updateDocument(Term term, Document doc, Analyzer analyzer)
Updates a document by first deleting the document(s) containing term and then adding the new document.

Field Details

DEFAULT_MAX_BUFFERED_DELETE_TERMS

public static final int DEFAULT_MAX_BUFFERED_DELETE_TERMS
Field Value:
1000

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_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 long WRITE_LOCK_TIMEOUT
Default value for the write lock timeout (1,000).

Constructor Details

IndexWriter

public IndexWriter(File path,
                   Analyzer a)
            throws IOException
Constructs an IndexWriter for the index in path, creating it first if it does not already exist, otherwise appending to the existing index. Text will be analyzed with a.
Parameters:
path - the path to the index directory
a - the analyzer to use

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)
            throws IOException
Constructs an IndexWriter for the index in path, creating it first if it does not already exist, otherwise appending to the existing index. Text will be analyzed with a.
Parameters:
path - the path to the index directory
a - the analyzer to use

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)
            throws IOException
Constructs an IndexWriter for the index in d, creating it first if it does not already exist, otherwise appending to the existing index. Text will be analyzed with a.
Parameters:
d - the index directory
a - the analyzer to use

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.

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(int)), and also periodically merges segments in the index (every setMergeFactor(int) 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). Most merges are small (merging the smallest segments together), but whenever a full merge occurs (all segments in the index, which is the worst case for temporary space usage) then the maximum free disk space required is the same as optimize().


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.

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


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.

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


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.

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.


addIndexesNoOptimize

public void addIndexesNoOptimize(Directory[] dirs)
            throws IOException
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.

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.


close

public void close()
            throws IOException
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.

deleteDocuments

public void deleteDocuments(Term term)
            throws IOException
Deletes the document(s) containing term.
Parameters:
term - the term to identify the documents to be deleted

deleteDocuments

public void deleteDocuments(Term[] terms)
            throws IOException
Deletes the document(s) containing any of the terms. All deletes are flushed at the same time.
Parameters:
terms - array of terms to identify the documents to be deleted

docCount

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

finalize

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

flush

public final void flush()
            throws IOException
Flush all in-memory buffered updates (adds and deletes) to the Directory.

getAnalyzer

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

getDefaultWriteLockTimeout

public static long getDefaultWriteLockTimeout()

getDirectory

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

getInfoStream

public PrintStream getInfoStream()

getMaxBufferedDeleteTerms

public int getMaxBufferedDeleteTerms()

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.

getWriteLockTimeout

public long getWriteLockTimeout()

maybeFlushRamSegments

protected final void maybeFlushRamSegments()
            throws IOException

numRamDocs

public final int numRamDocs()
Expert: Return the number of documents whose segments are currently cached in memory. Useful when calling flushRamSegments()

optimize

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

Note that this requires substantial temporary free space in the Directory (see LUCENE-764 for details):

  • If no readers/searchers are open against the index, then free space required is up to 1X the total size of the starting index. For example, if the starting index is 10 GB, then you must have up to 10 GB of free space before calling optimize.

  • If readers/searchers are using the index, then free space required is up to 2X the size of the starting index. This is because in addition to the 1X used by optimize, the original 1X of the starting index is still consuming space in the Directory as the readers are holding the segments files open. Even on Unix, where it will appear as if the files are gone ("ls" won't list them), they still consume storage due to "delete on last close" semantics.

    Furthermore, if some but not all readers re-open while the optimize is underway, this will cause > 2X temporary space to be consumed as those new readers will then hold open the partially optimized segments at that time. It is best not to re-open readers while optimize is running.

The actual temporary usage could be much less than these figures (it depends on many factors).

Once the optimize completes, the total size of the index will be less than the size of the starting index. It could be quite a bit smaller (if there were many pending deletes) or just slightly smaller.

If an Exception is hit during optimize(), for example due to disk full, the index will not be corrupt and no documents will have been lost. However, it may have been partially optimized (some segments were merged but not all), and it's possible that one of the segments in the index will be in non-compound format even when using compound file format. This will occur when the Exception is hit during conversion of the segment into compound format.


ramSizeInBytes

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

setDefaultWriteLockTimeout

public static void setDefaultWriteLockTimeout(long writeLockTimeout)
Sets the default (for any instance of IndexWriter) maximum time to wait for a write lock (in milliseconds).

setInfoStream

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

setMaxBufferedDeleteTerms

public void setMaxBufferedDeleteTerms(int maxBufferedDeleteTerms)

setMaxBufferedDocs

public void setMaxBufferedDocs(int maxBufferedDocs)
Determines the minimal number of documents required before the buffered in-memory documents are merged 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.

setWriteLockTimeout

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

updateDocument

public void updateDocument(Term term,
                           Document doc)
            throws IOException
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).
Parameters:
term - the term to identify the document(s) to be deleted
doc - the document to be added

updateDocument

public void updateDocument(Term term,
                           Document doc,
                           Analyzer analyzer)
            throws IOException
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).
Parameters:
term - the term to identify the document(s) to be deleted
doc - the document to be added
analyzer - the analyzer to use when analyzing the document

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