IndexReader (GATE Core 9.1-SNAPSHOT API)

java.lang.Object
- gate.creole.annic.apache.lucene.index.IndexReader

Direct Known Subclasses:

FilterIndexReader, MultiReader
```
public abstract class IndexReader
extends Object
```
IndexReader is an abstract class, providing an interface for accessing an index. Search of an index is done entirely through this abstract interface, so that any subclass which implements it is searchable.
Concrete subclasses of IndexReader are usually constructed with a call to the static method open(java.lang.String).
For efficiency, in this API documents are often referred to via document numbers, non-negative integers which each name a unique document in the index. These document numbers are ephemeral--they may change as documents are added to and deleted from an index. Clients should thus not rely on a given document having the same number between sessions.

Version:

$Id: IndexReader.java 529 2004-10-05 11:55:26Z niraj $

Author:

Doug Cutting

Constructor Summary

Constructors
Modifier Constructor and Description

protected IndexReader(Directory directory)
Constructor used if IndexReader is not owner of its directory.

Constructors
Modifier	Constructor and Description
`protected`	`IndexReader(Directory directory)` Constructor used if IndexReader is not owner of its directory.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`void`	`close()` Closes files associated with this index.
`protected void`	`commit()` Commit changes resulting from delete, undeleteAll, or setNorm operations
`void`	`delete(int docNum)` Deletes the document numbered `docNum`.
`int`	`delete(Term term)` Deletes all documents containing `term`.
`Directory`	`directory()` Returns the directory this index resides in.
`abstract int`	`docFreq(Term t)` Returns the number of documents containing the term `t`.
`protected abstract void`	`doClose()` Implements close.
`protected abstract void`	`doCommit()` Implements commit.
`abstract Document`	`document(int n)` Returns the stored fields of the `n`^th `Document` in this index.
`protected abstract void`	`doDelete(int docNum)` Implements deletion of the document numbered `docNum`.
`protected abstract void`	`doSetNorm(int doc, String field, byte value)` Implements setNorm in subclass.
`protected abstract void`	`doUndeleteAll()` Implements actual undeleteAll() in subclass.
`protected void`	`finalize()` Release the write lock, if needed.
`static long`	`getCurrentVersion(Directory directory)` Reads version number from segments files.
`static long`	`getCurrentVersion(File directory)` Reads version number from segments files.
`static long`	`getCurrentVersion(String directory)` Reads version number from segments files.
`abstract Collection`	`getFieldNames()` Returns a list of all unique field names that exist in the index pointed to by this IndexReader.
`abstract Collection`	`getFieldNames(boolean indexed)` Returns a list of all unique field names that exist in the index pointed to by this IndexReader.
`abstract Collection`	`getIndexedFieldNames(boolean storedTermVector)`
`abstract TermFreqVector`	`getTermFreqVector(int docNumber, String field)` Return a term frequency vector for the specified document and field.
`abstract TermFreqVector[]`	`getTermFreqVectors(int docNumber)` Return an array of term frequency vectors for the specified document.
`abstract boolean`	`hasDeletions()` Returns true if any documents have been deleted
`static boolean`	`indexExists(Directory directory)` Returns `true` if an index exists at the specified directory.
`static boolean`	`indexExists(File directory)` Returns `true` if an index exists at the specified directory.
`static boolean`	`indexExists(String directory)` Returns `true` if an index exists at the specified directory.
`abstract boolean`	`isDeleted(int n)` Returns true if document n has been deleted
`static boolean`	`isLocked(Directory directory)` Returns `true` iff the index in the named directory is currently locked.
`static boolean`	`isLocked(String directory)` Returns `true` iff the index in the named directory is currently locked.
`static long`	`lastModified(Directory directory)` Deprecated. Replaced by `getCurrentVersion(Directory)`
`static long`	`lastModified(File directory)` Deprecated. Replaced by `getCurrentVersion(File)`
`static long`	`lastModified(String directory)` Deprecated. Replaced by `getCurrentVersion(String)`
`abstract int`	`maxDoc()` Returns one greater than the largest possible document number.
`abstract byte[]`	`norms(String field)` Returns the byte-encoded normalization factor for the named field of every document.
`abstract void`	`norms(String field, byte[] bytes, int offset)` Reads the byte-encoded normalization factor for the named field of every document.
`abstract int`	`numDocs()` Returns the number of documents in this index.
`static IndexReader`	`open(Directory directory)` Returns an IndexReader reading the index in the given Directory.
`static IndexReader`	`open(File path)` Returns an IndexReader reading the index in an FSDirectory in the named path.
`static IndexReader`	`open(String path)` Returns an IndexReader reading the index in an FSDirectory in the named path.
`void`	`setNorm(int doc, String field, byte value)` Expert: Resets the normalization factor for the named field of the named document.
`void`	`setNorm(int doc, String field, float value)` Expert: Resets the normalization factor for the named field of the named document.
`abstract TermDocs`	`termDocs()` Returns an unpositioned `TermDocs` enumerator.
`TermDocs`	`termDocs(Term term)` Returns an enumeration of all the documents which contain `term`.
`abstract TermPositions`	`termPositions()` Returns an unpositioned `TermPositions` enumerator.
`TermPositions`	`termPositions(Term term)` Returns an enumeration of all the documents which contain `term`.
`abstract TermEnum`	`terms()` Returns an enumeration of all the terms in the index.
`abstract TermEnum`	`terms(Term t)` Returns an enumeration of all terms after a given term.
`void`	`undeleteAll()` Undeletes all documents currently marked as deleted in this index.
`static void`	`unlock(Directory directory)` Forcibly unlocks the index in the named directory.

Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - IndexReader
```
protected IndexReader(Directory directory)
```
    Constructor used if IndexReader is not owner of its directory. This is used for IndexReaders that are used within other IndexReaders that take care or locking directories.
    
    Parameters:
    
    directory - Directory where IndexReader files reside.
- Method Detail
  - open
```
public static IndexReader open(String path)
                        throws IOException
```
    Returns an IndexReader reading the index in an FSDirectory in the named path.
    
    Throws:
    
    IOException
  - open
```
public static IndexReader open(File path)
                        throws IOException
```
    Returns an IndexReader reading the index in an FSDirectory in the named path.
    
    Throws:
    
    IOException
  - open
```
public static IndexReader open(Directory directory)
                        throws IOException
```
    Returns an IndexReader reading the index in the given Directory.
    
    Throws:
    
    IOException
  - directory
```
public Directory directory()
```
    Returns the directory this index resides in.
  - lastModified
```
@Deprecated
public static long lastModified(String directory)
                                     throws IOException
```
    Deprecated. Replaced by getCurrentVersion(String)
    
    Returns the time the index in the named directory was last modified.
    Synchronization of IndexReader and IndexWriter instances is no longer done via time stamps of the segments file since the time resolution depends on the hardware platform. Instead, a version number is maintained within the segments file, which is incremented everytime when the index is changed.
    
    Throws:
    
    IOException
  - lastModified
```
@Deprecated
public static long lastModified(File directory)
                                     throws IOException
```
    Deprecated. Replaced by getCurrentVersion(File)
    
    Returns the time the index in the named directory was last modified.
    Synchronization of IndexReader and IndexWriter instances is no longer done via time stamps of the segments file since the time resolution depends on the hardware platform. Instead, a version number is maintained within the segments file, which is incremented everytime when the index is changed.
    
    Throws:
    
    IOException
  - lastModified
```
@Deprecated
public static long lastModified(Directory directory)
                                     throws IOException
```
    Deprecated. Replaced by getCurrentVersion(Directory)
    
    Returns the time the index in the named directory was last modified.
    Synchronization of IndexReader and IndexWriter instances is no longer done via time stamps of the segments file since the time resolution depends on the hardware platform. Instead, a version number is maintained within the segments file, which is incremented everytime when the index is changed.
    
    Throws:
    
    IOException
  - getCurrentVersion
```
public static long getCurrentVersion(String directory)
                              throws IOException
```
    Reads version number from segments files. The version number counts the number of changes of the index.
    
    Parameters:
    
    directory - where the index resides.
    
    Returns:
    
    version number.
    
    Throws:
    
    IOException - if segments file cannot be read
  - getCurrentVersion
```
public static long getCurrentVersion(File directory)
                              throws IOException
```
    Reads version number from segments files. The version number counts the number of changes of the index.
    
    Parameters:
    
    directory - where the index resides.
    
    Returns:
    
    version number.
    
    Throws:
    
    IOException - if segments file cannot be read
  - getCurrentVersion
```
public static long getCurrentVersion(Directory directory)
                              throws IOException
```
    Reads version number from segments files. The version number counts the number of changes of the index.
    
    Parameters:
    
    directory - where the index resides.
    
    Returns:
    
    version number.
    
    Throws:
    
    IOException - if segments file cannot be read.
  - getTermFreqVectors
```
public abstract TermFreqVector[] getTermFreqVectors(int docNumber)
                                             throws IOException
```
    Return an array of term frequency vectors for the specified document. The array contains a vector for each vectorized field in the document. Each vector contains terms and frequencies for all terms in a given vectorized field. If no such fields existed, the method returns null.
    
    Throws:
    
    IOException
    
    See Also:
    
    Field.isTermVectorStored()
  - getTermFreqVector
```
public abstract TermFreqVector getTermFreqVector(int docNumber,
                                                 String field)
                                          throws IOException
```
    Return a term frequency vector for the specified document and field. The vector returned contains terms and frequencies for those terms in the specified field of this document, if the field had storeTermVector flag set. If the flag was not set, the method returns null.
    
    Throws:
    
    IOException
    
    See Also:
    
    Field.isTermVectorStored()
  - indexExists
```
public static boolean indexExists(String directory)
```
    Returns true if an index exists at the specified directory. If the directory does not exist or if there is no index in it. false is returned.
    
    Parameters:
    
    directory - the directory to check for an index
    
    Returns:
    
    true if an index exists; false otherwise
  - indexExists
```
public static boolean indexExists(File directory)
```
    Returns true if an index exists at the specified directory. If the directory does not exist or if there is no index in it.
    
    Parameters:
    
    directory - the directory to check for an index
    
    Returns:
    
    true if an index exists; false otherwise
  - indexExists
```
public static boolean indexExists(Directory directory)
                           throws IOException
```
    Returns true if an index exists at the specified directory. If the directory does not exist or if there is no index in it.
    
    Parameters:
    
    directory - the directory to check for an index
    
    Returns:
    
    true if an index exists; false otherwise
    
    Throws:
    
    IOException - if there is a problem with accessing the index
  - numDocs
```
public abstract int numDocs()
```
    Returns the number of documents in this index.
  - maxDoc
```
public abstract int maxDoc()
```
    Returns one greater than the largest possible document number. This may be used to, e.g., determine how big to allocate an array which will have an element for every document number in an index.
  - document
```
public abstract Document document(int n)
                           throws IOException
```
    Returns the stored fields of the n^th Document in this index.
    
    Throws:
    
    IOException
  - isDeleted
```
public abstract boolean isDeleted(int n)
```
    Returns true if document n has been deleted
  - hasDeletions
```
public abstract boolean hasDeletions()
```
    Returns true if any documents have been deleted
  - norms
```
public abstract byte[] norms(String field)
                      throws IOException
```
    Returns the byte-encoded normalization factor for the named field of every document. This is used by the search code to score documents.
    
    Throws:
    
    IOException
    
    See Also:
    
    Field.setBoost(float)
  - norms
```
public abstract void norms(String field,
                           byte[] bytes,
                           int offset)
                    throws IOException
```
    Reads the byte-encoded normalization factor for the named field of every document. This is used by the search code to score documents.
    
    Throws:
    
    IOException
    
    See Also:
    
    Field.setBoost(float)
  - setNorm
```
public final void setNorm(int doc,
                          String field,
                          byte value)
                   throws IOException
```
    Expert: Resets the normalization factor for the named field of the named document. The norm represents the product of the field's boost and its length normalization. Thus, to preserve the length normalization values when resetting this, one should base the new value upon the old.
    
    Throws:
    
    IOException
    
    See Also:
    
    norms(String), Similarity.decodeNorm(byte)
  - doSetNorm
```
protected abstract void doSetNorm(int doc,
                                  String field,
                                  byte value)
                           throws IOException
```
    Implements setNorm in subclass.
    
    Throws:
    
    IOException
  - setNorm
```
public void setNorm(int doc,
                    String field,
                    float value)
             throws IOException
```
    Expert: Resets the normalization factor for the named field of the named document.
    
    Throws:
    
    IOException
    
    See Also:
    
    norms(String), Similarity.decodeNorm(byte)
  - terms
```
public abstract TermEnum terms()
                        throws IOException
```
    Returns an enumeration of all the terms in the index. The enumeration is ordered by Term.compareTo(). Each term is greater than all that precede it in the enumeration.
    
    Throws:
    
    IOException
  - terms
```
public abstract TermEnum terms(Term t)
                        throws IOException
```
    Returns an enumeration of all terms after a given term. The enumeration is ordered by Term.compareTo(). Each term is greater than all that precede it in the enumeration.
    
    Throws:
    
    IOException
  - docFreq
```
public abstract int docFreq(Term t)
                     throws IOException
```
    Returns the number of documents containing the term t.
    
    Throws:
    
    IOException
  - termDocs
```
public TermDocs termDocs(Term term)
                  throws IOException
```
    Returns an enumeration of all the documents which contain term. For each document, the document number, the frequency of the term in that document is also provided, for use in search scoring. Thus, this method implements the mapping:
    - Term => <docNum, freq>^*
    The enumeration is ordered by document number. Each document number is greater than all that precede it in the enumeration.
    Throws:
    
    IOException
  - termDocs
```
public abstract TermDocs termDocs()
                           throws IOException
```
    Returns an unpositioned TermDocs enumerator.
    
    Throws:
    
    IOException
  - termPositions
```
public TermPositions termPositions(Term term)
                            throws IOException
```
    Returns an enumeration of all the documents which contain term. For each document, in addition to the document number and frequency of the term in that document, a list of all of the ordinal positions of the term in the document is available. Thus, this method implements the mapping:
    - Term => <docNum, freq, <pos₁, pos₂, ... pos_freq-1> >^*
    This positional information faciliates phrase and proximity searching. The enumeration is ordered by document number. Each document number is greater than all that precede it in the enumeration.
    Throws:
    
    IOException
  - termPositions
```
public abstract TermPositions termPositions()
                                     throws IOException
```
    Returns an unpositioned TermPositions enumerator.
    
    Throws:
    
    IOException
  - delete
```
public final void delete(int docNum)
                  throws IOException
```
    Deletes the document numbered docNum. Once a document is deleted it will not appear in TermDocs or TermPostitions enumerations. Attempts to read its field with the document(int) method will result in an error. The presence of this document may still be reflected in the docFreq(gate.creole.annic.apache.lucene.index.Term) statistic, though this will be corrected eventually as the index is further modified.
    
    Throws:
    
    IOException
  - doDelete
```
protected abstract void doDelete(int docNum)
                          throws IOException
```
    Implements deletion of the document numbered docNum. Applications should call delete(int) or delete(Term).
    
    Throws:
    
    IOException
  - delete
```
public final int delete(Term term)
                 throws IOException
```
    Deletes all documents containing term. This is useful if one uses a document field to hold a unique ID string for the document. Then to delete such a document, one merely constructs a term with the appropriate field and the unique ID string as its text and passes it to this method. Returns the number of documents deleted.
    
    Throws:
    
    IOException
  - undeleteAll
```
public final void undeleteAll()
                       throws IOException
```
    Undeletes all documents currently marked as deleted in this index.
    
    Throws:
    
    IOException
  - doUndeleteAll
```
protected abstract void doUndeleteAll()
                               throws IOException
```
    Implements actual undeleteAll() in subclass.
    
    Throws:
    
    IOException
  - commit
```
protected final void commit()
                     throws IOException
```
    Commit changes resulting from delete, undeleteAll, or setNorm operations
    
    Throws:
    
    IOException
  - doCommit
```
protected abstract void doCommit()
                          throws IOException
```
    Implements commit.
    
    Throws:
    
    IOException
  - close
```
public final void close()
                 throws IOException
```
    Closes files associated with this index. Also saves any new deletions to disk. No other methods should be called after this has been called.
    
    Throws:
    
    IOException
  - doClose
```
protected abstract void doClose()
                         throws IOException
```
    Implements close.
    
    Throws:
    
    IOException
  - finalize
```
protected final void finalize()
                       throws IOException
```
    Release the write lock, if needed.
    
    Overrides:
    
    finalize in class Object
    
    Throws:
    
    IOException
  - getFieldNames
```
public abstract Collection getFieldNames()
                                  throws IOException
```
    Returns a list of all unique field names that exist in the index pointed to by this IndexReader.
    
    Returns:
    
    Collection of Strings indicating the names of the fields
    
    Throws:
    
    IOException - if there is a problem with accessing the index
  - getFieldNames
```
public abstract Collection getFieldNames(boolean indexed)
                                  throws IOException
```
    Returns a list of all unique field names that exist in the index pointed to by this IndexReader. The boolean argument specifies whether the fields returned are indexed or not.
    
    Parameters:
    
    indexed - true if only indexed fields should be returned; false if only unindexed fields should be returned.
    
    Returns:
    
    Collection of Strings indicating the names of the fields
    
    Throws:
    
    IOException - if there is a problem with accessing the index
  - getIndexedFieldNames
```
public abstract Collection getIndexedFieldNames(boolean storedTermVector)
```
    Parameters:
    
    storedTermVector - if true, returns only Indexed fields that have term vector info, else only indexed fields without term vector info
    
    Returns:
    
    Collection of Strings indicating the names of the fields
  - isLocked
```
public static boolean isLocked(Directory directory)
                        throws IOException
```
    Returns true iff the index in the named directory is currently locked.
    
    Parameters:
    
    directory - the directory to check for a lock
    
    Throws:
    
    IOException - if there is a problem with accessing the index
  - isLocked
```
public static boolean isLocked(String directory)
                        throws IOException
```
    Returns true iff the index in the named directory is currently locked.
    
    Parameters:
    
    directory - the directory to check for a lock
    
    Throws:
    
    IOException - if there is a problem with accessing the index
  - unlock
```
public static void unlock(Directory directory)
                   throws IOException
```
    Forcibly unlocks the index in the named directory.
    Caution: this should only be used by failure recovery code, when it is known that no other process nor thread is in fact currently accessing this index.
    
    Throws:
    
    IOException

Class IndexReader

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

IndexReader

Method Detail

open

open

open

directory

lastModified

lastModified

lastModified

getCurrentVersion

getCurrentVersion

getCurrentVersion

getTermFreqVectors

getTermFreqVector

indexExists

indexExists

indexExists

numDocs

maxDoc

document

isDeleted

hasDeletions

norms

norms

setNorm

doSetNorm

setNorm

terms

terms

docFreq

termDocs

termDocs

termPositions

termPositions

delete

doDelete

delete

undeleteAll

doUndeleteAll

commit

doCommit

close

doClose

finalize

getFieldNames

getFieldNames

getIndexedFieldNames

isLocked

isLocked

unlock