org.apache.lucene.index

## Class ParallelLeafReader

- java.lang.Object
- - org.apache.lucene.index.IndexReader
  - - org.apache.lucene.index.LeafReader
    - - org.apache.lucene.index.ParallelLeafReader

- All Implemented Interfaces:
    Closeable, AutoCloseable

      public class ParallelLeafReader
      extends LeafReader

  An `LeafReader` which reads multiple, parallel indexes. Each index added must have the same number of documents, but typically each contains different fields. Deletions are taken from the first reader. Each document contains the union of the fields of all documents with the same document number. When searching, matches for a query term are from the first index added that has the field.

  This is useful, e.g., with collections that have large fields which change rarely and small fields that change more frequently. The smaller fields may be re-indexed in a new index and both indexes may be searched together.

  Warning: It is up to you to make sure all indexes are created and modified the same way. For example, if you add documents to one index, you need to add the same documents in the same order to the other indexes. Failure to do so will result in undefined behavior.

- - ### Nested Class Summary

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

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

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `ParallelLeafReader(boolean closeSubReaders, LeafReader... readers)` Create a ParallelLeafReader based on the provided readers.
    `ParallelLeafReader(boolean closeSubReaders, LeafReader[] readers, LeafReader[] storedFieldsReaders)` Expert: create a ParallelLeafReader based on the provided readers and storedFieldReaders; when a document is loaded, only storedFieldsReaders will be used.
    `ParallelLeafReader(LeafReader... readers)` Create a ParallelLeafReader based on the provided readers; auto-closes the given readers on `IndexReader.close()`.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `checkIntegrity()` Checks consistency of this reader.
    `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.
    `BinaryDocValues` | `getBinaryDocValues(String field)` Returns `BinaryDocValues` for this field, or null if no binary doc values were indexed for this field.
    `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.
    `FieldInfos` | `getFieldInfos()` Get the `FieldInfos` describing all fields in this reader.
    `Bits` | `getLiveDocs()` Returns the `Bits` representing live (not deleted) docs.
    `LeafMetaData` | `getMetaData()` Return metadata about this leaf.
    `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 numeric doc values were indexed for this field.
    `LeafReader[]` | `getParallelReaders()` Returns the `LeafReader`s that were passed on init.
    `PointValues` | `getPointValues(String fieldName)` Returns the `PointValues` used for numeric or spatial searches for the given field, or null if there are no point fields.
    `IndexReader.CacheHelper` | `getReaderCacheHelper()` Optional method: Return a `IndexReader.CacheHelper` that can be used to cache based on the content of this reader.
    `SortedDocValues` | `getSortedDocValues(String field)` Returns `SortedDocValues` for this field, or null if no `SortedDocValues` were indexed for this field.
    `SortedNumericDocValues` | `getSortedNumericDocValues(String field)` Returns `SortedNumericDocValues` for this field, or null if no `SortedNumericDocValues` were indexed for this field.
    `SortedSetDocValues` | `getSortedSetDocValues(String field)` Returns `SortedSetDocValues` for this field, or null if no `SortedSetDocValues` were indexed for this field.
    `Fields` | `getTermVectors(int docID)` Retrieve term vectors for this document, or null if term vectors were not indexed.
    `int` | `maxDoc()` Returns one greater than the largest possible document number.
    `int` | `numDocs()` Returns the number of documents in this index.
    `Terms` | `terms(String field)` Returns the `Terms` index for this field, or null if it has none.
    `String` | `toString()`

    - ### 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`

- - ### Constructor Detail

    - #### ParallelLeafReader

          public ParallelLeafReader(LeafReader... readers)
                             throws IOException

      Create a ParallelLeafReader based on the provided readers; auto-closes the given readers on `IndexReader.close()`.
      Throws:
        `IOException`

    - #### ParallelLeafReader

          public ParallelLeafReader(boolean closeSubReaders,
                                    LeafReader... readers)
                             throws IOException

      Create a ParallelLeafReader based on the provided readers.
      Throws:
        `IOException`

    - #### ParallelLeafReader

          public ParallelLeafReader(boolean closeSubReaders,
                                    LeafReader[] readers,
                                    LeafReader[] storedFieldsReaders)
                             throws IOException

      Expert: create a ParallelLeafReader based on the provided readers and storedFieldReaders; when a document is loaded, only storedFieldsReaders will be used.
      Throws:
        `IOException`

  - ### Method Detail

    - #### toString

          public String toString()

      Overrides:
        `toString` in class `Object`

    - #### getFieldInfos

          public FieldInfos getFieldInfos()

      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.

      NOTE: the returned field numbers will likely not correspond to the actual field numbers in the underlying readers, and codec metadata (`FieldInfo.getAttribute(String)` will be unavailable.

      Specified by:
        `getFieldInfos` in class `LeafReader`

    - #### 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`

    - #### terms

          public Terms terms(String field)
                      throws IOException

      Description copied from class: `LeafReader`
      Returns the `Terms` index for this field, or null if it has none.
      Specified by:
        `terms` in class `LeafReader`
      Throws:
        `IOException`

    - #### 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`

    - #### 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`

    - #### 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`

    - #### 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`

    - #### 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`

    - #### doClose

          protected void doClose()
                          throws IOException

      Description copied from class: `IndexReader`
      Implements close.
      Specified by:
        `doClose` in class `IndexReader`
      Throws:
        `IOException`

    - #### getNumericDocValues

          public NumericDocValues getNumericDocValues(String field)
                                               throws IOException

      Description copied from class: `LeafReader`
      Returns `NumericDocValues` for this field, or null if no numeric doc values were indexed for this field. The returned instance should only be used by a single thread.
      Specified by:
        `getNumericDocValues` in class `LeafReader`
      Throws:
        `IOException`

    - #### getBinaryDocValues

          public BinaryDocValues getBinaryDocValues(String field)
                                             throws IOException

      Description copied from class: `LeafReader`
      Returns `BinaryDocValues` for this field, or null if no binary doc values were indexed for this field. The returned instance should only be used by a single thread.
      Specified by:
        `getBinaryDocValues` in class `LeafReader`
      Throws:
        `IOException`

    - #### getSortedDocValues

          public SortedDocValues getSortedDocValues(String field)
                                             throws IOException

      Description copied from class: `LeafReader`
      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 `LeafReader`
      Throws:
        `IOException`

    - #### getSortedNumericDocValues

          public SortedNumericDocValues getSortedNumericDocValues(String field)
                                                           throws IOException

      Description copied from class: `LeafReader`
      Returns `SortedNumericDocValues` for this field, or null if no `SortedNumericDocValues` were indexed for this field. The returned instance should only be used by a single thread.
      Specified by:
        `getSortedNumericDocValues` in class `LeafReader`
      Throws:
        `IOException`

    - #### getSortedSetDocValues

          public SortedSetDocValues getSortedSetDocValues(String field)
                                                   throws IOException

      Description copied from class: `LeafReader`
      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 `LeafReader`
      Throws:
        `IOException`

    - #### getNormValues

          public NumericDocValues getNormValues(String field)
                                         throws IOException

      Description copied from class: `LeafReader`
      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 `LeafReader`
      Throws:
        `IOException`

    - #### getPointValues

          public PointValues getPointValues(String fieldName)
                                     throws IOException

      Description copied from class: `LeafReader`
      Returns the `PointValues` used for numeric or spatial searches for the given field, or null if there are no point fields.
      Specified by:
        `getPointValues` in class `LeafReader`
      Throws:
        `IOException`

    - #### 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.

      Specified by:
        `checkIntegrity` in class `LeafReader`
      Throws:
        `IOException`

    - #### getParallelReaders

          public LeafReader[] getParallelReaders()

      Returns the `LeafReader`s that were passed on init.

    - #### getMetaData

          public LeafMetaData getMetaData()

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

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