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java.lang.Object
org.apache.lucene.index.IndexReader
public abstract class IndexReader
extends java.lang.Object
open
.
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.
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Method Summary | |
void |
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protected void |
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void |
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int | |
Directory |
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protected abstract void |
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protected abstract void |
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protected abstract void |
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protected abstract void |
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protected abstract void |
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abstract int | |
abstract Document |
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protected void |
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static long |
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static long |
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static long |
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abstract Collection |
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abstract Collection |
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abstract Collection |
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abstract TermFreqVector |
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abstract TermFreqVector[] |
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abstract boolean |
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static boolean |
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static boolean |
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static boolean |
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abstract boolean |
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static boolean |
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static boolean | |
static long |
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static long |
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static long |
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abstract int |
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abstract byte[] |
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abstract void |
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abstract int |
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static IndexReader |
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static IndexReader |
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static IndexReader | |
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void |
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abstract TermDocs | |
TermDocs | |
abstract TermPositions |
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TermPositions |
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abstract TermEnum |
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abstract TermEnum | |
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static void |
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.
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.
protected final void commit() throws IOException
Commit changes resulting from delete, undeleteAll, or setNorm operations
public final void delete(int docNum) throws IOException
Deletes the document numbereddocNum
. Once a document is deleted it will not appear in TermDocs or TermPostitions enumerations. Attempts to read its field with thedocument(int)
method will result in an error. The presence of this document may still be reflected in thedocFreq(Term)
statistic, though this will be corrected eventually as the index is further modified.
public final int delete(Term term) throws IOException
Deletes all documents containingterm
. 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.
protected abstract void doClose() throws IOException
Implements close.
protected abstract void doCommit() throws IOException
Implements commit.
protected abstract void doDelete(int docNum) throws IOException
Implements deletion of the document numbereddocNum
. Applications should calldelete(int)
ordelete(Term)
.
protected abstract void doSetNorm(int doc, String field, byte value) throws IOException
Implements setNorm in subclass.
protected abstract void doUndeleteAll() throws IOException
Implements actual undeleteAll() in subclass.
public abstract int docFreq(Term t) throws IOException
Returns the number of documents containing the termt
.
public abstract Document document(int n) throws IOException
Returns the stored fields of then
thDocument
in this index.
protected final void finalize() throws IOException
Release the write lock, if needed.
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.
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.
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.
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
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
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
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.
- See Also:
Field.isTermVectorStored()
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.
- See Also:
Field.isTermVectorStored()
public abstract boolean hasDeletions()
Returns true if any documents have been deleted
public static boolean indexExists(File directory)
Returnstrue
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
public static boolean indexExists(String directory)
Returnstrue
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
public static boolean indexExists(Directory directory) throws IOException
Returnstrue
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
public abstract boolean isDeleted(int n)
Returns true if document n has been deleted
public static boolean isLocked(String directory) throws IOException
Returnstrue
iff the index in the named directory is currently locked.
- Parameters:
directory
- the directory to check for a lock
public static boolean isLocked(Directory directory) throws IOException
Returnstrue
iff the index in the named directory is currently locked.
- Parameters:
directory
- the directory to check for a lock
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.
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.
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.
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.
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.
- See Also:
Field.setBoost(float)
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.
- See Also:
Field.setBoost(float)
public abstract int numDocs()
Returns the number of documents in this index.
public static IndexReader open(File path) throws IOException
Returns an IndexReader reading the index in an FSDirectory in the named path.
public static IndexReader open(String path) throws IOException
Returns an IndexReader reading the index in an FSDirectory in the named path.
public static IndexReader open(Directory directory) throws IOException
Returns an IndexReader reading the index in the given Directory.
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'sboost
and itslength normalization
. Thus, to preserve the length normalization values when resetting this, one should base the new value upon the old.
- See Also:
norms(String)
,Similarity.decodeNorm(byte)
public void setNorm(int doc, String field, float value) throws IOException
Expert: Resets the normalization factor for the named field of the named document.
- See Also:
norms(String)
,Similarity.decodeNorm(byte)
public abstract TermDocs termDocs() throws IOException
Returns an unpositionedTermDocs
enumerator.
public TermDocs termDocs(Term term) throws IOException
Returns an enumeration of all the documents which containterm
. 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.
public abstract TermPositions termPositions() throws IOException
Returns an unpositionedTermPositions
enumerator.
public TermPositions termPositions(Term term) throws IOException
Returns an enumeration of all the documents which containterm
. 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:12freq-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.
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.
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.
public final void undeleteAll() throws IOException
Undeletes all documents currently marked as deleted in this index.
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.