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Class Description
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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.
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Class Variables
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WRITE_LOCK_TIMEOUT
public static long
Default value is 1000. Use org.apache.lucene.writeLockTimeout
system property to override.
COMMIT_LOCK_TIMEOUT
public static long
Default value is 10000. Use org.apache.lucene.commitLockTimeout
system property to override.
WRITE_LOCK_NAME
public static final String
No description available for this variable.
COMMIT_LOCK_NAME
public static final String
No description available for this variable.
DEFAULT_MERGE_FACTOR
public static final int
Default value is 10. Use org.apache.lucene.mergeFactor
system property to override.
DEFAULT_MIN_MERGE_DOCS
public static final int
Default value is 10. Use org.apache.lucene.minMergeDocs
system property to override.
DEFAULT_MAX_MERGE_DOCS
public static final int
Default value is MAX_VALUE.
Use org.apache.lucene.maxMergeDocs system property to override.
DEFAULT_MAX_FIELD_LENGTH
public static final int
Default value is 10000. Use org.apache.lucene.maxFieldLength
system property to override.
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Instance Variables
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maxFieldLength
public int
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
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
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 org.apache.lucene.store.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
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 MAX_VALUE.
infoStream
public PrintStream
If non-null, information about merges will be printed to this.
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Constructors
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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.
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.
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.
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Class Methods
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None declared in this class.
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Instance Methods
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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.
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.
addIndexes
public synchronized 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.
addIndexes
public synchronized 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.
close
public synchronized void close(
)
throws
IOException
Flushes all changes to an index and closes all associated files.
docCount
public synchronized 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.
getSimilarity
public Similarity getSimilarity(
)
Expert: Return the Similarity implementation used by this IndexWriter.
This defaults to the current value of getDefault().
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.
optimize
public synchronized void optimize(
)
throws
IOException
Merges all segments together into a single segment, optimizing an index
for search.
setSimilarity
public void setSimilarity(
Similarity similarity
)
Expert: Set the Similarity implementation used by this IndexWriter.
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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