IndexWriter (GATE Core 8.6 API)

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

Fields
Modifier and Type	Field and Description
`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

Constructors
Constructor and Description
`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

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`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

Class IndexWriter

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

WRITE_LOCK_TIMEOUT

COMMIT_LOCK_TIMEOUT

WRITE_LOCK_NAME

COMMIT_LOCK_NAME

DEFAULT_MERGE_FACTOR

DEFAULT_MIN_MERGE_DOCS

DEFAULT_MAX_MERGE_DOCS

DEFAULT_MAX_FIELD_LENGTH

maxFieldLength

mergeFactor

minMergeDocs

maxMergeDocs

infoStream

Constructor Detail

IndexWriter

IndexWriter

IndexWriter

Method Detail

getUseCompoundFile

setUseCompoundFile

setSimilarity

getSimilarity

close

finalize

getAnalyzer

docCount

addDocument

addDocument

optimize

addIndexes

addIndexes