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## org.apache.lucene.index
Class SegmentReader

    java.lang.Object
      org.apache.lucene.index.IndexReader
          org.apache.lucene.index.SegmentReader

All Implemented Interfaces:
  Closeable, Cloneable

    public class SegmentReader

extends IndexReader
implements Cloneable

IndexReader implementation over a single segment.

Instances pointing to the same segment (but with different deletes, etc) may share the same core data.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary
`static interface` | `SegmentReader.CoreClosedListener` Called when the shared core for this SegmentReader is closed.

Nested classes/interfaces inherited from class org.apache.lucene.index.IndexReader
`IndexReader.ReaderClosedListener`

Field Summary
`protected boolean` | `readOnly` Deprecated.

Fields inherited from class org.apache.lucene.index.IndexReader
`hasChanges`

Constructor Summary
`SegmentReader()`

Method Summary
`void` | `addCoreClosedListener(SegmentReader.CoreClosedListener listener)` Expert: adds a CoreClosedListener to this reader's shared core
`Object` | `clone()` Efficiently clones the IndexReader (sharing most internal state).
`IndexReader` | `clone(boolean openReadOnly)` Deprecated.
`protected BitVector` | `cloneDeletedDocs(BitVector bv)` Deprecated.
`protected byte[]` | `cloneNormBytes(byte[] bytes)` Deprecated.
`Directory` | `directory()` Returns the directory this index resides in.
`int` | `docFreq(Term t)` Returns the number of documents containing the term `t`.
`protected void` | `doClose()` Implements close.
`protected void` | `doCommit(Map<String,String> commitUserData)` Deprecated.
`Document` | `document(int n, FieldSelector fieldSelector)` Get the `Document` at the `n` th position.
`protected void` | `doDelete(int docNum)` Deprecated.
`protected IndexReader` | `doOpenIfChanged()` If the index has changed since it was opened, open and return a new reader; else, return `null`.
`protected IndexReader` | `doOpenIfChanged(boolean openReadOnly)` Deprecated.
`protected void` | `doSetNorm(int doc, String field, byte value)` Deprecated.
`protected void` | `doUndeleteAll()` Deprecated.
`static SegmentReader` | `get(boolean readOnly, Directory dir, SegmentInfo si, int readBufferSize, boolean doOpenStores, int termInfosIndexDivisor)`
`static SegmentReader` | `get(boolean readOnly, SegmentInfo si, int termInfosIndexDivisor)`
`Object` | `getCoreCacheKey()` Expert
`Object` | `getDeletesCacheKey()` Expert.
`FieldInfos` | `getFieldInfos()` Get the `FieldInfos` describing all fields in this reader.
`String` | `getSegmentName()` Return the name of the segment this reader is reading.
`TermFreqVector` | `getTermFreqVector(int docNumber, String field)` Return a term frequency vector for the specified document and field.
`void` | `getTermFreqVector(int docNumber, String field, TermVectorMapper mapper)` Load the Term Vector into a user-defined data structure instead of relying on the parallel arrays of the `TermFreqVector`.
`void` | `getTermFreqVector(int docNumber, TermVectorMapper mapper)` Map all the term vectors for all fields in a Document
`TermFreqVector[]` | `getTermFreqVectors(int docNumber)` Return an array of term frequency vectors for the specified document.
`int` | `getTermInfosIndexDivisor()` For IndexReader implementations that use TermInfosReader to read terms, this returns the current indexDivisor as specified when the reader was opened.
`long` | `getUniqueTermCount()` Returns the number of unique terms (across all fields) in this reader.
`boolean` | `hasDeletions()` Returns true if any documents have been deleted
`boolean` | `hasNorms(String field)` Returns true if there are norms stored for this field.
`boolean` | `isDeleted(int n)` Returns true if document n has been deleted
`int` | `maxDoc()` Returns one greater than the largest possible document number.
`byte[]` | `norms(String field)` Returns the byte-encoded normalization factor for the named field of every document.
`void` | `norms(String field, byte[] bytes, int offset)` Read norms into a pre-allocated array.
`int` | `numDocs()` Returns the number of documents in this index.
`TermDocs` | `rawTermDocs(Term term)` Expert: returns an enumeration of the documents that contain `term`, including deleted documents (which are normally filtered out).
`void` | `removeCoreClosedListener(SegmentReader.CoreClosedListener listener)` Expert: removes a CoreClosedListener from this reader's shared core
`TermDocs` | `termDocs()` Returns an unpositioned `TermDocs` enumerator.
`TermDocs` | `termDocs(Term term)` Returns an enumeration of all the documents which contain `term`.
`TermPositions` | `termPositions()` Returns an unpositioned `TermPositions` enumerator.
`TermEnum` | `terms()` Returns an enumeration of all the terms in the index.
`TermEnum` | `terms(Term t)` Returns an enumeration of all terms starting at a given term.
`String` | `toString()`

Methods inherited from class org.apache.lucene.index.IndexReader
`acquireWriteLock, addReaderClosedListener, close, commit, commit, decRef, deleteDocument, deleteDocuments, document, doOpenIfChanged, doOpenIfChanged, ensureOpen, flush, flush, getCommitUserData, getCommitUserData, getCurrentVersion, getIndexCommit, getRefCount, getSequentialSubReaders, getVersion, incRef, indexExists, isCurrent, isOptimized, lastModified, listCommits, numDeletedDocs, open, open, open, open, open, open, open, open, open, open, open, openIfChanged, openIfChanged, openIfChanged, openIfChanged, removeReaderClosedListener, reopen, reopen, reopen, reopen, setNorm, setNorm, termPositions, tryIncRef, undeleteAll`

Methods inherited from class java.lang.Object
`equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

### readOnly

    @Deprecated
    protected boolean readOnly

  Deprecated.

Constructor Detail

### SegmentReader

    public SegmentReader()

Method Detail

### get

    public static SegmentReader get(boolean readOnly,
                                    SegmentInfo si,
                                    int termInfosIndexDivisor)
                             throws CorruptIndexException,
                                    IOException

  Throws:
    `CorruptIndexException` - if the index is corrupt
    `IOException` - if there is a low-level IO error

### get

    public static SegmentReader get(boolean readOnly,
                                    Directory dir,
                                    SegmentInfo si,
                                    int readBufferSize,
                                    boolean doOpenStores,
                                    int termInfosIndexDivisor)
                             throws CorruptIndexException,
                                    IOException

  Throws:
    `CorruptIndexException` - if the index is corrupt
    `IOException` - if there is a low-level IO error

### cloneNormBytes

    @Deprecated
    protected byte[] cloneNormBytes(byte[] bytes)

  Deprecated.

  Clones the norm bytes. May be overridden by subclasses. New and experimental.

  Parameters:
    `bytes` - Byte array to clone
  Returns:
    New BitVector

### cloneDeletedDocs

    @Deprecated
    protected BitVector cloneDeletedDocs(BitVector bv)

  Deprecated.

  Clones the deleteDocs BitVector. May be overridden by subclasses. New and experimental.

  Parameters:
    `bv` - BitVector to clone
  Returns:
    New BitVector

### clone

    public final Object clone()

  Description copied from class: `IndexReader`
  Efficiently clones the IndexReader (sharing most internal state).

  On cloning a reader with pending changes (deletions, norms), the original reader transfers its write lock to the cloned reader. This means only the cloned reader may make further changes to the index, and commit the changes to the index on close, but the old reader still reflects all changes made up until it was cloned.

  Like `IndexReader.openIfChanged(IndexReader)`, it's safe to make changes to either the original or the cloned reader: all shared mutable state obeys "copy on write" semantics to ensure the changes are not seen by other readers.

  Overrides:
    `clone` in class `IndexReader`

### clone

    @Deprecated
    public final IndexReader clone(boolean openReadOnly)
                            throws CorruptIndexException,
                                   IOException

  Deprecated.

  Clones the IndexReader and optionally changes readOnly. A readOnly reader cannot open a writeable reader.

  Overrides:
    `clone` in class `IndexReader`
  Throws:
    `CorruptIndexException` - if the index is corrupt
    `IOException` - if there is a low-level IO error

### doOpenIfChanged

    protected IndexReader doOpenIfChanged()
                                   throws CorruptIndexException,
                                          IOException

  Description copied from class: `IndexReader`
  If the index has changed since it was opened, open and return a new reader; else, return `null`.

  Overrides:
    `doOpenIfChanged` in class `IndexReader`
  Throws:
    `CorruptIndexException`
    `IOException`
  See Also:
    `IndexReader.openIfChanged(IndexReader)`

### doOpenIfChanged

    @Deprecated
    protected IndexReader doOpenIfChanged(boolean openReadOnly)
                                   throws CorruptIndexException,
                                          IOException

  Deprecated.

  If the index has changed since it was opened, open and return a new reader; else, return `null`.

  Overrides:
    `doOpenIfChanged` in class `IndexReader`
  Throws:
    `CorruptIndexException`
    `IOException`
  See Also:
    `IndexReader.openIfChanged(IndexReader, boolean)`

### doCommit

    @Deprecated
    protected void doCommit(Map<String,String> commitUserData)
                     throws IOException

  Deprecated.

  Implements commit.

  Specified by:
    `doCommit` in class `IndexReader`
  Throws:
    `IOException`

### doClose

    protected void doClose()
                    throws IOException

  Description copied from class: `IndexReader`
  Implements close.

  Specified by:
    `doClose` in class `IndexReader`
  Throws:
    `IOException`

### hasDeletions

    public boolean hasDeletions()

  Description copied from class: `IndexReader`
  Returns true if any documents have been deleted

  Specified by:
    `hasDeletions` in class `IndexReader`

### doDelete

    @Deprecated
    protected void doDelete(int docNum)

  Deprecated.

  Implements deletion of the document numbered `docNum`. Applications should call `IndexReader.deleteDocument(int)` or `IndexReader.deleteDocuments(Term)`.

  Specified by:
    `doDelete` in class `IndexReader`

### doUndeleteAll

    @Deprecated
    protected void doUndeleteAll()

  Deprecated.

  Implements actual undeleteAll() in subclass.

  Specified by:
    `doUndeleteAll` in class `IndexReader`

### terms

    public TermEnum terms()

  Description copied from class: `IndexReader`
  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. Note that after calling terms(), `TermEnum.next()` must be called on the resulting enumeration before calling other methods such as `TermEnum.term()`.

  Specified by:
    `terms` in class `IndexReader`

### terms

    public TermEnum terms(Term t)
                   throws IOException

  Description copied from class: `IndexReader`
  Returns an enumeration of all terms starting at a given term. If the given term does not exist, the enumeration is positioned at the first term greater than the supplied term. The enumeration is ordered by Term.compareTo(). Each term is greater than all that precede it in the enumeration.

  Specified by:
    `terms` in class `IndexReader`
  Throws:
    `IOException` - if there is a low-level IO error

### getFieldInfos

    public FieldInfos getFieldInfos()

  Description copied from class: `IndexReader`
  Get the `FieldInfos` describing all fields in this reader. NOTE: do not make any changes to the returned FieldInfos!

  Specified by:
    `getFieldInfos` in class `IndexReader`

### document

    public Document document(int n,
                             FieldSelector fieldSelector)
                      throws CorruptIndexException,
                             IOException

  Description copied from class: `IndexReader`
  Get the `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.

  NOTE: for performance reasons, this method does not check if the requested document is deleted, and therefore asking for a deleted document may yield unspecified results. Usually this is not required, however you can call `IndexReader.isDeleted(int)` with the requested document ID to verify the document is not deleted.

  Specified by:
    `document` in class `IndexReader`
  Parameters:
    `n` - Get the document at the `n`th position
    `fieldSelector` - 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.
  Returns:
    The stored fields of the `Document` at the nth position
  Throws:
    `CorruptIndexException` - if the index is corrupt
    `IOException` - if there is a low-level IO error
  See Also:
    `Fieldable`, `FieldSelector`, `SetBasedFieldSelector`, `LoadFirstFieldSelector`

### isDeleted

    public boolean isDeleted(int n)

  Description copied from class: `IndexReader`
  Returns true if document n has been deleted

  Specified by:
    `isDeleted` in class `IndexReader`

### termDocs

    public TermDocs termDocs(Term term)
                      throws IOException

  Description copied from class: `IndexReader`
  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. If term is null, then all non-deleted docs are returned with freq=1. 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.

  Overrides:
    `termDocs` in class `IndexReader`
  Throws:
    `IOException` - if there is a low-level IO error

### rawTermDocs

    public TermDocs rawTermDocs(Term term)
                         throws IOException

  Expert: returns an enumeration of the documents that contain `term`, including deleted documents (which are normally filtered out).

  Throws:
    `IOException`
  WARNING: This API is experimental and might change in incompatible ways in the next release.

### termDocs

    public TermDocs termDocs()
                      throws IOException

  Description copied from class: `IndexReader`
  Returns an unpositioned `TermDocs` enumerator.

  Note: the TermDocs returned is unpositioned. Before using it, ensure that you first position it with `TermDocs.seek(Term)` or `TermDocs.seek(TermEnum)`.

  Specified by:
    `termDocs` in class `IndexReader`
  Throws:
    `IOException` - if there is a low-level IO error

### termPositions

    public TermPositions termPositions()
                                throws IOException

  Description copied from class: `IndexReader`
  Returns an unpositioned `TermPositions` enumerator.

  Specified by:
    `termPositions` in class `IndexReader`
  Throws:
    `IOException` - if there is a low-level IO error

### docFreq

    public int docFreq(Term t)
                throws IOException

  Description copied from class: `IndexReader`
  Returns the number of documents containing the term `t`.

  Specified by:
    `docFreq` in class `IndexReader`
  Throws:
    `IOException` - if there is a low-level IO error

### numDocs

    public int numDocs()

  Description copied from class: `IndexReader`
  Returns the number of documents in this index.

  Specified by:
    `numDocs` in class `IndexReader`

### maxDoc

    public int maxDoc()

  Description copied from class: `IndexReader`
  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.

  Specified by:
    `maxDoc` in class `IndexReader`

### hasNorms

    public boolean hasNorms(String field)

  Description copied from class: `IndexReader`
  Returns true if there are norms stored for this field.

  Overrides:
    `hasNorms` in class `IndexReader`

### norms

    public byte[] norms(String field)
                 throws IOException

  Description copied from class: `IndexReader`
  Returns the byte-encoded normalization factor for the named field of every document. This is used by the search code to score documents. Returns null if norms were not indexed for this field.

  Specified by:
    `norms` in class `IndexReader`
  Throws:
    `IOException`
  See Also:
    `AbstractField.setBoost(float)`

### doSetNorm

    @Deprecated
    protected void doSetNorm(int doc,
                                        String field,
                                        byte value)
                      throws IOException

  Deprecated.

  Implements setNorm in subclass.

  Specified by:
    `doSetNorm` in class `IndexReader`
  Throws:
    `IOException`

### norms

    public void norms(String field,
                      byte[] bytes,
                      int offset)
               throws IOException

  Read norms into a pre-allocated array.

  Specified by:
    `norms` in class `IndexReader`
  Throws:
    `IOException`
  See Also:
    `AbstractField.setBoost(float)`

### getTermFreqVector

    public TermFreqVector getTermFreqVector(int docNumber,
                                            String field)
                                     throws IOException

  Return a term frequency vector for the specified document and field. The vector returned contains term numbers and frequencies for all 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.

  Specified by:
    `getTermFreqVector` in class `IndexReader`
  Parameters:
    `docNumber` - document for which the term frequency vector is returned
    `field` - field for which the term frequency vector is returned.
  Returns:
    term frequency vector May be null if field does not exist in the specified document or term vector was not stored.
  Throws:
    `IOException`
  See Also:
    `Field.TermVector`

### getTermFreqVector

    public void getTermFreqVector(int docNumber,
                                  String field,
                                  TermVectorMapper mapper)
                           throws IOException

  Description copied from class: `IndexReader`
  Load the Term Vector into a user-defined data structure instead of relying on the parallel arrays of the `TermFreqVector`.

  Specified by:
    `getTermFreqVector` in class `IndexReader`
  Parameters:
    `docNumber` - The number of the document to load the vector for
    `field` - The name of the field to load
    `mapper` - The `TermVectorMapper` to process the vector. Must not be null
  Throws:
    `IOException` - if term vectors cannot be accessed or if they do not exist on the field and doc. specified.

### getTermFreqVector

    public void getTermFreqVector(int docNumber,
                                  TermVectorMapper mapper)
                           throws IOException

  Description copied from class: `IndexReader`
  Map all the term vectors for all fields in a Document

  Specified by:
    `getTermFreqVector` in class `IndexReader`
  Parameters:
    `docNumber` - The number of the document to load the vector for
    `mapper` - The `TermVectorMapper` to process the vector. Must not be null
  Throws:
    `IOException` - if term vectors cannot be accessed or if they do not exist on the field and doc. specified.

### getTermFreqVectors

    public 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 vector contains term numbers and frequencies for all terms in a given vectorized field. If no such fields existed, the method returns null.

  Specified by:
    `getTermFreqVectors` in class `IndexReader`
  Parameters:
    `docNumber` - document for which term frequency vectors are returned
  Returns:
    array of term frequency vectors. May be null if no term vectors have been stored for the specified document.
  Throws:
    `IOException`
  See Also:
    `Field.TermVector`

### toString

    public String toString()

  Overrides:
    `toString` in class `IndexReader`

### getSegmentName

    public String getSegmentName()

  Return the name of the segment this reader is reading.

### directory

    public Directory directory()

  Returns the directory this index resides in.

  Overrides:
    `directory` in class `IndexReader`

### getCoreCacheKey

    public final Object getCoreCacheKey()

  Description copied from class: `IndexReader`
  Expert

  Overrides:
    `getCoreCacheKey` in class `IndexReader`

### getDeletesCacheKey

    public Object getDeletesCacheKey()

  Description copied from class: `IndexReader`
  Expert. Warning: this returns null if the reader has no deletions

  Overrides:
    `getDeletesCacheKey` in class `IndexReader`

### getUniqueTermCount

    public long getUniqueTermCount()

  Description copied from class: `IndexReader`
  Returns the number of unique terms (across all fields) in this reader. This method returns long, even though internally Lucene cannot handle more than 2^31 unique terms, for a possible future when this limitation is removed.

  Overrides:
    `getUniqueTermCount` in class `IndexReader`

### getTermInfosIndexDivisor

    public int getTermInfosIndexDivisor()

  Description copied from class: `IndexReader`
  For IndexReader implementations that use TermInfosReader to read terms, this returns the current indexDivisor as specified when the reader was opened.

  Overrides:
    `getTermInfosIndexDivisor` in class `IndexReader`

### addCoreClosedListener

    public void addCoreClosedListener(SegmentReader.CoreClosedListener listener)

  Expert: adds a CoreClosedListener to this reader's shared core

### removeCoreClosedListener

    public void removeCoreClosedListener(SegmentReader.CoreClosedListener listener)

  Expert: removes a CoreClosedListener from this reader's shared core

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