Package org.apache.lucene.index

Class 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.

    • Constructor Detail

      • 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

      • 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

      • 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

      • 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

      • searchNearestVectors

        public TopDocs searchNearestVectors​(String fieldName,
                                    float[] target,
                                    int k,
                                    Bits acceptDocs,
                                    int visitedLimit)
                             throws IOException
        Description copied from class: LeafReader
        Return the k nearest neighbor documents as determined by comparison of their vector values for this field, to the given vector, by the field's similarity function. The score of each document is derived from the vector similarity in a way that ensures scores are positive and that a larger score corresponds to a higher ranking.

        The search is allowed to be approximate, meaning the results are not guaranteed to be the true k closest neighbors. For large values of k (for example when k is close to the total number of documents), the search may also retrieve fewer than k documents.

        The returned TopDocs will contain a ScoreDoc for each nearest neighbor, sorted in order of their similarity to the query vector (decreasing scores). The TotalHits contains the number of documents visited during the search. If the search stopped early because it hit visitedLimit, it is indicated through the relation TotalHits.Relation.GREATER_THAN_OR_EQUAL_TO.

        Specified by:
        searchNearestVectors in class LeafReader
        Parameters:
        fieldName - the vector field to search
        target - the vector-valued query
        k - the number of docs to return
        acceptDocs - Bits that represents the allowed documents to match, or null if they are all allowed to match.
        visitedLimit - the maximum number of nodes that the search is allowed to visit
        Returns:
        the k nearest neighbor documents, along with their (searchStrategy-specific) scores.
        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 LeafReaders that were passed on init.