org.apache.lucene.index

## Class SegmentReader

- java.lang.Object
- - org.apache.lucene.index.IndexReader
  - - org.apache.lucene.index.LeafReader
    - - org.apache.lucene.index.CodecReader
      - - org.apache.lucene.index.SegmentReader

- All Implemented Interfaces:
    Closeable, AutoCloseable, Accountable

      public final class SegmentReader
      extends CodecReader

  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

    - ### Nested classes/interfaces inherited from class org.apache.lucene.index.IndexReader

      `IndexReader.CacheHelper, IndexReader.CacheKey, IndexReader.ClosedListener`

  - ### Field Summary

    - ### Fields inherited from interface org.apache.lucene.util.Accountable

      `NULL_ACCOUNTABLE`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `checkIntegrity()` Checks consistency of this reader.
    `Directory` | `directory()` Returns the directory this index resides in.
    `protected void` | `doClose()` Implements close.
    `IndexReader.CacheHelper` | `getCoreCacheHelper()` Optional method: Return a `IndexReader.CacheHelper` that can be used to cache based on the content of this leaf regardless of deletions.
    `DocValuesProducer` | `getDocValuesReader()` Expert: retrieve underlying DocValuesProducer
    `FieldInfos` | `getFieldInfos()` Get the `FieldInfos` describing all fields in this reader.
    `StoredFieldsReader` | `getFieldsReader()` Expert: retrieve thread-private StoredFieldsReader
    `Bits` | `getHardLiveDocs()` Returns the live docs that are not hard-deleted.
    `Bits` | `getLiveDocs()` Returns the `Bits` representing live (not deleted) docs.
    `LeafMetaData` | `getMetaData()` Return metadata about this leaf.
    `NormsProducer` | `getNormsReader()` Expert: retrieve underlying NormsProducer
    `PointsReader` | `getPointsReader()` Expert: retrieve underlying PointsReader
    `FieldsProducer` | `getPostingsReader()` Expert: retrieve underlying FieldsProducer
    `IndexReader.CacheHelper` | `getReaderCacheHelper()` Optional method: Return a `IndexReader.CacheHelper` that can be used to cache based on the content of this reader.
    `SegmentCommitInfo` | `getSegmentInfo()` Return the SegmentInfoPerCommit of the segment this reader is reading.
    `String` | `getSegmentName()` Return the name of the segment this reader is reading.
    `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.
    `String` | `toString()`

    - ### Methods inherited from class org.apache.lucene.index.CodecReader

      `document, getBinaryDocValues, getChildResources, getNormValues, getNumericDocValues, getPointValues, getSortedDocValues, getSortedNumericDocValues, getSortedSetDocValues, getTermVectors, ramBytesUsed, terms`

    - ### Methods inherited from class org.apache.lucene.index.LeafReader

      `docFreq, getContext, getDocCount, getSumDocFreq, getSumTotalTermFreq, postings, postings, totalTermFreq`

    - ### Methods inherited from class org.apache.lucene.index.IndexReader

      `close, decRef, document, document, ensureOpen, equals, getRefCount, getTermVector, hasDeletions, hashCode, incRef, leaves, numDeletedDocs, registerParentReader, tryIncRef`

    - ### Methods inherited from class java.lang.Object

      `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- - ### Method Detail

    - #### getLiveDocs

          public Bits getLiveDocs()

      Description copied from class: `LeafReader`
      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 `LeafReader`

    - #### doClose

          protected void doClose()
                          throws IOException

      Description copied from class: `IndexReader`
      Implements close.
      Overrides:
        `doClose` in class `CodecReader`
      Throws:
        `IOException`

    - #### getFieldInfos

          public FieldInfos getFieldInfos()

      Description copied from class: `LeafReader`
      Get the `FieldInfos` describing all fields in this reader. Note: Implementations should cache the FieldInfos instance returned by this method such that subsequent calls to this method return the same instance.
      Specified by:
        `getFieldInfos` in class `LeafReader`

    - #### numDocs

          public int numDocs()

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

      NOTE: This operation may run in O(maxDoc). Implementations that can't return this number in constant-time should cache it.

      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()

      Description copied from class: `CodecReader`
      Expert: retrieve thread-private TermVectorsReader
      Specified by:
        `getTermVectorsReader` in class `CodecReader`

    - #### getFieldsReader

          public StoredFieldsReader getFieldsReader()

      Description copied from class: `CodecReader`
      Expert: retrieve thread-private StoredFieldsReader
      Specified by:
        `getFieldsReader` in class `CodecReader`

    - #### getPointsReader

          public PointsReader getPointsReader()

      Description copied from class: `CodecReader`
      Expert: retrieve underlying PointsReader
      Specified by:
        `getPointsReader` in class `CodecReader`

    - #### getNormsReader

          public NormsProducer getNormsReader()

      Description copied from class: `CodecReader`
      Expert: retrieve underlying NormsProducer
      Specified by:
        `getNormsReader` in class `CodecReader`

    - #### getDocValuesReader

          public DocValuesProducer getDocValuesReader()

      Description copied from class: `CodecReader`
      Expert: retrieve underlying DocValuesProducer
      Specified by:
        `getDocValuesReader` in class `CodecReader`

    - #### getPostingsReader

          public FieldsProducer getPostingsReader()

      Description copied from class: `CodecReader`
      Expert: retrieve underlying FieldsProducer
      Specified by:
        `getPostingsReader` in class `CodecReader`

    - #### 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 SegmentCommitInfo getSegmentInfo()

      Return the SegmentInfoPerCommit of the segment this reader is reading.

    - #### directory

          public Directory directory()

      Returns the directory this index resides in.

    - #### getReaderCacheHelper

          public IndexReader.CacheHelper getReaderCacheHelper()

      Description copied from class: `IndexReader`
      Optional method: Return a `IndexReader.CacheHelper` that can be used to cache based on the content of this reader. Two readers that have different data or different sets of deleted documents will be considered different.

      A return value of `null` indicates that this reader is not suited for caching, which is typically the case for short-lived wrappers that alter the content of the wrapped reader.

      Specified by:
        `getReaderCacheHelper` in class `IndexReader`

    - #### getCoreCacheHelper

          public IndexReader.CacheHelper getCoreCacheHelper()

      Description copied from class: `LeafReader`
      Optional method: Return a `IndexReader.CacheHelper` that can be used to cache based on the content of this leaf regardless of deletions. Two readers that have the same data but different sets of deleted documents or doc values updates may be considered equal. Consider using `IndexReader.getReaderCacheHelper()` if you need deletions or dv updates to be taken into account.

      A return value of `null` indicates that this reader is not suited for caching, which is typically the case for short-lived wrappers that alter the content of the wrapped leaf reader.

      Specified by:
        `getCoreCacheHelper` in class `LeafReader`

    - #### getMetaData

          public LeafMetaData getMetaData()

      Description copied from class: `LeafReader`
      Return metadata about this leaf.
      Specified by:
        `getMetaData` in class `LeafReader`

    - #### getHardLiveDocs

          public Bits getHardLiveDocs()

      Returns the live docs that are not hard-deleted. This is an expert API to be used with soft-deletes to filter out document that hard deleted for instance due to aborted documents or to distinguish soft and hard deleted documents ie. a rolled back tombstone.
      WARNING: This API is experimental and might change in incompatible ways in the next release.

    - #### checkIntegrity

          public void checkIntegrity()
                              throws IOException

      Description copied from class: `LeafReader`
      Checks consistency of this reader.

      Note that this may be costly in terms of I/O, e.g. may involve computing a checksum value against large data files.

      Overrides:
        `checkIntegrity` in class `CodecReader`
      Throws:
        `IOException`

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