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java.lang.Objectorg.apache.lucene.index.IndexReader
public abstract class IndexReader
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
one of the static open()
methods, e.g. open(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.
An IndexReader can be opened on a directory for which an IndexWriter is opened already, but it cannot be used to delete documents from the index then.
Nested Class Summary | |
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static class |
IndexReader.FieldOption
|
Constructor Summary | |
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protected |
IndexReader(Directory directory)
Constructor used if IndexReader is not owner of its directory. |
Method Summary | |
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void |
close()
Closes files associated with this index. |
protected void |
commit()
Commit changes resulting from delete, undeleteAll, or setNorm operations If an exception is hit, then either no changes or all changes will have been committed to the index (transactional semantics). |
void |
deleteDocument(int docNum)
Deletes the document numbered docNum . |
int |
deleteDocuments(Term term)
Deletes all documents that have a given term indexed. |
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. |
Document |
document(int n)
Returns the stored fields of the n th
Document in this index. |
abstract Document |
document(int n,
FieldSelector fieldSelector)
Get the Document at the n th position. |
protected abstract void |
doDelete(int docNum)
Implements deletion of the document numbered docNum . |
protected abstract void |
doSetNorm(int doc,
java.lang.String field,
byte value)
Implements setNorm in subclass. |
protected abstract void |
doUndeleteAll()
Implements actual undeleteAll() in subclass. |
protected void |
ensureOpen()
|
protected void |
finalize()
Release the write lock, if needed. |
static long |
getCurrentVersion(Directory directory)
Reads version number from segments files. |
static long |
getCurrentVersion(java.io.File directory)
Reads version number from segments files. |
static long |
getCurrentVersion(java.lang.String directory)
Reads version number from segments files. |
abstract java.util.Collection |
getFieldNames(IndexReader.FieldOption fldOption)
Get a list of unique field names that exist in this index and have the specified field option information. |
abstract TermFreqVector |
getTermFreqVector(int docNumber,
java.lang.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. |
long |
getVersion()
Version number when this IndexReader was opened. |
abstract boolean |
hasDeletions()
Returns true if any documents have been deleted |
boolean |
hasNorms(java.lang.String field)
Returns true if there are norms stored for this field. |
static boolean |
indexExists(Directory directory)
Returns true if an index exists at the specified directory. |
static boolean |
indexExists(java.io.File directory)
Returns true if an index exists at the specified directory. |
static boolean |
indexExists(java.lang.String directory)
Returns true if an index exists at the specified directory. |
boolean |
isCurrent()
Check whether this IndexReader is still using the current (i.e., most recently committed) version of the index. |
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(java.lang.String directory)
Returns true iff the index in the named directory is
currently locked. |
boolean |
isOptimized()
Checks is the index is optimized (if it has a single segment and no deletions) |
static long |
lastModified(Directory directory2)
Returns the time the index in the named directory was last modified. |
static long |
lastModified(java.io.File fileDirectory)
Returns the time the index in the named directory was last modified. |
static long |
lastModified(java.lang.String directory)
Returns the time the index in the named directory was last modified. |
static void |
main(java.lang.String[] args)
Prints the filename and size of each file within a given compound file. |
abstract int |
maxDoc()
Returns one greater than the largest possible document number. |
abstract byte[] |
norms(java.lang.String field)
Returns the byte-encoded normalization factor for the named field of every document. |
abstract void |
norms(java.lang.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(Directory directory,
IndexDeletionPolicy deletionPolicy)
Expert: returns an IndexReader reading the index in the given Directory, with a custom IndexDeletionPolicy . |
static IndexReader |
open(java.io.File path)
Returns an IndexReader reading the index in an FSDirectory in the named path. |
static IndexReader |
open(java.lang.String path)
Returns an IndexReader reading the index in an FSDirectory in the named path. |
void |
setNorm(int doc,
java.lang.String field,
byte value)
Expert: Resets the normalization factor for the named field of the named document. |
void |
setNorm(int doc,
java.lang.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 starting at 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 |
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clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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protected IndexReader(Directory directory)
directory
- Directory where IndexReader files reside.Method Detail |
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protected final void ensureOpen() throws AlreadyClosedException
AlreadyClosedException
- if this IndexReader is closedpublic static IndexReader open(java.lang.String path) throws CorruptIndexException, java.io.IOException
path
- the path to the index directory
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic static IndexReader open(java.io.File path) throws CorruptIndexException, java.io.IOException
path
- the path to the index directory
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic static IndexReader open(Directory directory) throws CorruptIndexException, java.io.IOException
directory
- the index directory
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic static IndexReader open(Directory directory, IndexDeletionPolicy deletionPolicy) throws CorruptIndexException, java.io.IOException
IndexDeletionPolicy
.
directory
- the index directorydeletionPolicy
- a custom deletion policy (only used
if you use this reader to perform deletes or to set
norms); see IndexWriter
for details.
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic Directory directory()
public static long lastModified(java.lang.String directory) throws CorruptIndexException, java.io.IOException
isCurrent()
instead.
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic static long lastModified(java.io.File fileDirectory) throws CorruptIndexException, java.io.IOException
isCurrent()
instead.
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic static long lastModified(Directory directory2) throws CorruptIndexException, java.io.IOException
isCurrent()
instead.
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic static long getCurrentVersion(java.lang.String directory) throws CorruptIndexException, java.io.IOException
directory
- where the index resides.
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic static long getCurrentVersion(java.io.File directory) throws CorruptIndexException, java.io.IOException
directory
- where the index resides.
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic static long getCurrentVersion(Directory directory) throws CorruptIndexException, java.io.IOException
directory
- where the index resides.
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic long getVersion()
public boolean isCurrent() throws CorruptIndexException, java.io.IOException
false
, in which case you must open a new
IndexReader in order to see the changes. See the
description of the autoCommit
flag which controls when the IndexWriter
actually commits changes to the index.
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic boolean isOptimized()
true
if the index is optimized; false
otherwisepublic abstract TermFreqVector[] getTermFreqVectors(int docNumber) throws java.io.IOException
docNumber
- document for which term frequency vectors are returned
java.io.IOException
- if index cannot be accessedField.TermVector
public abstract TermFreqVector getTermFreqVector(int docNumber, java.lang.String field) throws java.io.IOException
docNumber
- document for which the term frequency vector is returnedfield
- field for which the term frequency vector is returned.
java.io.IOException
- if index cannot be accessedField.TermVector
public static boolean indexExists(java.lang.String directory)
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.
directory
- the directory to check for an index
true
if an index exists; false
otherwisepublic static boolean indexExists(java.io.File directory)
true
if an index exists at the specified directory.
If the directory does not exist or if there is no index in it.
directory
- the directory to check for an index
true
if an index exists; false
otherwisepublic static boolean indexExists(Directory directory) throws java.io.IOException
true
if an index exists at the specified directory.
If the directory does not exist or if there is no index in it.
directory
- the directory to check for an index
true
if an index exists; false
otherwise
java.io.IOException
- if there is a problem with accessing the indexpublic abstract int numDocs()
public abstract int maxDoc()
public Document document(int n) throws CorruptIndexException, java.io.IOException
n
th
Document
in this index.
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorpublic abstract Document document(int n, FieldSelector fieldSelector) throws CorruptIndexException, java.io.IOException
Document
at the n
th position. The FieldSelector
may be used to determine what Field
s to load and how they should be loaded.
NOTE: If this Reader (more specifically, the underlying FieldsReader
) is closed before the lazy Field
is
loaded an exception may be thrown. If you want the value of a lazy Field
to be available after closing you must
explicitly load it or fetch the Document again with a new loader.
n
- Get the document at the n
th positionfieldSelector
- The FieldSelector
to use to determine what Fields should be loaded on the Document. May be null, in which case all Fields will be loaded.
Document
at the nth position
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorFieldable
,
FieldSelector
,
SetBasedFieldSelector
,
LoadFirstFieldSelector
public abstract boolean isDeleted(int n)
public abstract boolean hasDeletions()
public boolean hasNorms(java.lang.String field) throws java.io.IOException
java.io.IOException
public abstract byte[] norms(java.lang.String field) throws java.io.IOException
java.io.IOException
AbstractField.setBoost(float)
public abstract void norms(java.lang.String field, byte[] bytes, int offset) throws java.io.IOException
java.io.IOException
AbstractField.setBoost(float)
public final void setNorm(int doc, java.lang.String field, byte value) throws StaleReaderException, CorruptIndexException, LockObtainFailedException, java.io.IOException
boost
and its length normalization
. Thus, to preserve the length normalization
values when resetting this, one should base the new value upon the old.
StaleReaderException
- if the index has changed
since this reader was opened
CorruptIndexException
- if the index is corrupt
LockObtainFailedException
- if another writer
has this index open (write.lock
could not
be obtained)
java.io.IOException
- if there is a low-level IO errornorms(String)
,
Similarity.decodeNorm(byte)
protected abstract void doSetNorm(int doc, java.lang.String field, byte value) throws CorruptIndexException, java.io.IOException
CorruptIndexException
java.io.IOException
public void setNorm(int doc, java.lang.String field, float value) throws StaleReaderException, CorruptIndexException, LockObtainFailedException, java.io.IOException
StaleReaderException
- if the index has changed
since this reader was opened
CorruptIndexException
- if the index is corrupt
LockObtainFailedException
- if another writer
has this index open (write.lock
could not
be obtained)
java.io.IOException
- if there is a low-level IO errornorms(String)
,
Similarity.decodeNorm(byte)
public abstract TermEnum terms() throws java.io.IOException
TermEnum.next()
must be called
on the resulting enumeration before calling other methods such as
TermEnum.term()
.
java.io.IOException
- if there is a low-level IO errorpublic abstract TermEnum terms(Term t) throws java.io.IOException
java.io.IOException
- if there is a low-level IO errorpublic abstract int docFreq(Term t) throws java.io.IOException
t
.
java.io.IOException
- if there is a low-level IO errorpublic TermDocs termDocs(Term term) throws java.io.IOException
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:
The enumeration is ordered by document number. Each document number is greater than all that precede it in the enumeration.
java.io.IOException
- if there is a low-level IO errorpublic abstract TermDocs termDocs() throws java.io.IOException
TermDocs
enumerator.
java.io.IOException
- if there is a low-level IO errorpublic TermPositions termPositions(Term term) throws java.io.IOException
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:
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.
java.io.IOException
- if there is a low-level IO errorpublic abstract TermPositions termPositions() throws java.io.IOException
TermPositions
enumerator.
java.io.IOException
- if there is a low-level IO errorpublic final void deleteDocument(int docNum) throws StaleReaderException, CorruptIndexException, LockObtainFailedException, java.io.IOException
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(org.apache.lucene.index.Term)
statistic, though
this will be corrected eventually as the index is further modified.
StaleReaderException
- if the index has changed
since this reader was opened
CorruptIndexException
- if the index is corrupt
LockObtainFailedException
- if another writer
has this index open (write.lock
could not
be obtained)
java.io.IOException
- if there is a low-level IO errorprotected abstract void doDelete(int docNum) throws CorruptIndexException, java.io.IOException
docNum
.
Applications should call deleteDocument(int)
or deleteDocuments(Term)
.
CorruptIndexException
java.io.IOException
public final int deleteDocuments(Term term) throws StaleReaderException, CorruptIndexException, LockObtainFailedException, java.io.IOException
term
indexed.
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.
See deleteDocument(int)
for information about when this deletion will
become effective.
StaleReaderException
- if the index has changed
since this reader was opened
CorruptIndexException
- if the index is corrupt
LockObtainFailedException
- if another writer
has this index open (write.lock
could not
be obtained)
java.io.IOException
- if there is a low-level IO errorpublic final void undeleteAll() throws StaleReaderException, CorruptIndexException, LockObtainFailedException, java.io.IOException
StaleReaderException
- if the index has changed
since this reader was opened
LockObtainFailedException
- if another writer
has this index open (write.lock
could not
be obtained)
CorruptIndexException
- if the index is corrupt
java.io.IOException
- if there is a low-level IO errorprotected abstract void doUndeleteAll() throws CorruptIndexException, java.io.IOException
CorruptIndexException
java.io.IOException
protected final void commit() throws java.io.IOException
java.io.IOException
- if there is a low-level IO errorprotected abstract void doCommit() throws java.io.IOException
java.io.IOException
public final void close() throws java.io.IOException
java.io.IOException
- if there is a low-level IO errorprotected abstract void doClose() throws java.io.IOException
java.io.IOException
protected void finalize() throws java.lang.Throwable
finalize
in class java.lang.Object
java.lang.Throwable
public abstract java.util.Collection getFieldNames(IndexReader.FieldOption fldOption)
fldOption
- specifies which field option should be available for the returned fields
IndexReader.FieldOption
public static boolean isLocked(Directory directory) throws java.io.IOException
true
iff the index in the named directory is
currently locked.
directory
- the directory to check for a lock
java.io.IOException
- if there is a low-level IO errorpublic static boolean isLocked(java.lang.String directory) throws java.io.IOException
true
iff the index in the named directory is
currently locked.
directory
- the directory to check for a lock
java.io.IOException
- if there is a low-level IO errorpublic static void unlock(Directory directory) throws java.io.IOException
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.
java.io.IOException
public static void main(java.lang.String[] args)
args
- Usage: org.apache.lucene.index.IndexReader [-extract] <cfsfile>
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