## org.apache.lucene.index
Class SegmentReader

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

All Implemented Interfaces:
  Closeable

    public final class SegmentReader

extends AtomicReader

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`

Constructor Summary
`SegmentReader(SegmentInfoPerCommit si, int termInfosIndexDivisor, IOContext context)` Constructs a new SegmentReader with a new core.

Method Summary
`void` `addCoreClosedListener(SegmentReader.CoreClosedListener listener)` Expert: adds a CoreClosedListener to this reader's shared core
`Directory` `directory()` Returns the directory this index resides in.
`protected void` `doClose()` Implements close.
`void` `document(int docID, StoredFieldVisitor visitor)` Expert: visits the fields of a stored document, for custom processing/loading of each field.
`Fields` `fields()` Returns `Fields` for this reader.
`BinaryDocValues` `getBinaryDocValues(String field)` Returns `BinaryDocValues` for this field, or null if no `BinaryDocValues` were indexed for this field.
`Object` `getCombinedCoreAndDeletesKey()` Expert: Returns a key for this IndexReader that also includes deletions, so FieldCache/CachingWrapperFilter can find it again.
`Object` `getCoreCacheKey()` Expert: Returns a key for this IndexReader, so FieldCache/CachingWrapperFilter can find it again.
`FieldInfos` `getFieldInfos()` Get the `FieldInfos` describing all fields in this reader.
`StoredFieldsReader` `getFieldsReader()` Expert: retrieve thread-private `StoredFieldsReader`
`Bits` `getLiveDocs()` Returns the `Bits` representing live (not deleted) docs.
`NumericDocValues` `getNormValues(String field)` Returns `NumericDocValues` representing norms for this field, or null if no `NumericDocValues` were indexed.
`NumericDocValues` `getNumericDocValues(String field)` Returns `NumericDocValues` for this field, or null if no `NumericDocValues` were indexed for this field.
`SegmentInfoPerCommit` `getSegmentInfo()` Return the SegmentInfoPerCommit of the segment this reader is reading.
`String` `getSegmentName()` Return the name of the segment this reader is reading.
`SortedDocValues` `getSortedDocValues(String field)` Returns `SortedDocValues` for this field, or null if no `SortedDocValues` were indexed for this field.
`SortedSetDocValues` `getSortedSetDocValues(String field)` Returns `SortedSetDocValues` for this field, or null if no `SortedSetDocValues` were indexed for this field.
`int` `getTermInfosIndexDivisor()` Returns term infos index divisor originally passed to `SegmentReader(SegmentInfoPerCommit, int, IOContext)`.
`Fields` `getTermVectors(int docID)` Retrieve term vectors for this document, or null if term vectors were not indexed.
`TermVectorsReader` `getTermVectorsReader()` Expert: retrieve thread-private `TermVectorsReader`
`int` `maxDoc()` Returns one greater than the largest possible document number.
`int` `numDocs()` Returns the number of documents in this index.
`void` `removeCoreClosedListener(SegmentReader.CoreClosedListener listener)` Expert: removes a CoreClosedListener from this reader's shared core
`String` `toString()`

Methods inherited from class org.apache.lucene.index.AtomicReader
`docFreq, getContext, getDocCount, getSumDocFreq, getSumTotalTermFreq, hasNorms, termDocsEnum, termPositionsEnum, terms, totalTermFreq`

Methods inherited from class org.apache.lucene.index.IndexReader
`addReaderClosedListener, close, decRef, document, document, ensureOpen, equals, getRefCount, getTermVector, hasDeletions, hashCode, incRef, leaves, numDeletedDocs, open, open, open, open, open, registerParentReader, removeReaderClosedListener, tryIncRef`

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

Constructor Detail

### SegmentReader

    public SegmentReader(SegmentInfoPerCommit si,
                         int termInfosIndexDivisor,
                         IOContext context)
                  throws IOException

  Constructs a new SegmentReader with a new core.

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

Method Detail

### getLiveDocs

    public Bits getLiveDocs()

  Description copied from class: `AtomicReader`
  Returns the `Bits` representing live (not deleted) docs. A set bit indicates the doc ID has not been deleted. If this method returns null it means there are no deleted documents (all documents are live). The returned instance has been safely published for use by multiple threads without additional synchronization.

  Specified by:
    `getLiveDocs` in class `AtomicReader`

### doClose

    protected void doClose()
                    throws IOException

  Description copied from class: `IndexReader`
  Implements close.

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

### getFieldInfos

    public FieldInfos getFieldInfos()

  Description copied from class: `AtomicReader`
  Get the `FieldInfos` describing all fields in this reader.

  Specified by:
    `getFieldInfos` in class `AtomicReader`

### getFieldsReader

    public StoredFieldsReader getFieldsReader()

  Expert: retrieve thread-private `StoredFieldsReader`

  NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

### document

    public void document(int docID,
                         StoredFieldVisitor visitor)
                  throws IOException

  Description copied from class: `IndexReader`
  Expert: visits the fields of a stored document, for custom processing/loading of each field. If you simply want to load all fields, use `IndexReader.document(int)`. If you want to load a subset, use `DocumentStoredFieldVisitor`.

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

### fields

    public Fields fields()

  Description copied from class: `AtomicReader`
  Returns `Fields` for this reader. This method may return null if the reader has no postings.

  Specified by:
    `fields` in class `AtomicReader`

### 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`

### getTermVectorsReader

    public TermVectorsReader getTermVectorsReader()

  Expert: retrieve thread-private `TermVectorsReader`

  NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

### getTermVectors

    public Fields getTermVectors(int docID)
                          throws IOException

  Description copied from class: `IndexReader`
  Retrieve term vectors for this document, or null if term vectors were not indexed. The returned Fields instance acts like a single-document inverted index (the docID will be 0).

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

### toString

    public String toString()

  Overrides:
    `toString` in class `Object`

### getSegmentName

    public String getSegmentName()

  Return the name of the segment this reader is reading.

### getSegmentInfo

    public SegmentInfoPerCommit getSegmentInfo()

  Return the SegmentInfoPerCommit of the segment this reader is reading.

### directory

    public Directory directory()

  Returns the directory this index resides in.

### getCoreCacheKey

    public Object getCoreCacheKey()

  Description copied from class: `IndexReader`
  Expert: Returns a key for this IndexReader, so FieldCache/CachingWrapperFilter can find it again. This key must not have equals()/hashCode() methods, so "equals" means "identical".

  Overrides:
    `getCoreCacheKey` in class `IndexReader`

### getCombinedCoreAndDeletesKey

    public Object getCombinedCoreAndDeletesKey()

  Description copied from class: `IndexReader`
  Expert: Returns a key for this IndexReader that also includes deletions, so FieldCache/CachingWrapperFilter can find it again. This key must not have equals()/hashCode() methods, so "equals" means "identical".

  Overrides:
    `getCombinedCoreAndDeletesKey` in class `IndexReader`

### getTermInfosIndexDivisor

    public int getTermInfosIndexDivisor()

  Returns term infos index divisor originally passed to `SegmentReader(SegmentInfoPerCommit, int, IOContext)`.

### getNumericDocValues

    public NumericDocValues getNumericDocValues(String field)
                                         throws IOException

  Description copied from class: `AtomicReader`
  Returns `NumericDocValues` for this field, or null if no `NumericDocValues` were indexed for this field. The returned instance should only be used by a single thread.

  Specified by:
    `getNumericDocValues` in class `AtomicReader`
  Throws:
    `IOException`

### getBinaryDocValues

    public BinaryDocValues getBinaryDocValues(String field)
                                       throws IOException

  Description copied from class: `AtomicReader`
  Returns `BinaryDocValues` for this field, or null if no `BinaryDocValues` were indexed for this field. The returned instance should only be used by a single thread.

  Specified by:
    `getBinaryDocValues` in class `AtomicReader`
  Throws:
    `IOException`

### getSortedDocValues

    public SortedDocValues getSortedDocValues(String field)
                                       throws IOException

  Description copied from class: `AtomicReader`
  Returns `SortedDocValues` for this field, or null if no `SortedDocValues` were indexed for this field. The returned instance should only be used by a single thread.

  Specified by:
    `getSortedDocValues` in class `AtomicReader`
  Throws:
    `IOException`

### getSortedSetDocValues

    public SortedSetDocValues getSortedSetDocValues(String field)
                                             throws IOException

  Description copied from class: `AtomicReader`
  Returns `SortedSetDocValues` for this field, or null if no `SortedSetDocValues` were indexed for this field. The returned instance should only be used by a single thread.

  Specified by:
    `getSortedSetDocValues` in class `AtomicReader`
  Throws:
    `IOException`

### getNormValues

    public NumericDocValues getNormValues(String field)
                                   throws IOException

  Description copied from class: `AtomicReader`
  Returns `NumericDocValues` representing norms for this field, or null if no `NumericDocValues` were indexed. The returned instance should only be used by a single thread.

  Specified by:
    `getNormValues` in class `AtomicReader`
  Throws:
    `IOException`

### 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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