Package org.apache.lucene.index

Class BaseCompositeReader<R extends IndexReader>

  • All Implemented Interfaces:
    Closeable, AutoCloseable
    Direct Known Subclasses:
    DirectoryReader, MultiReader, ParallelCompositeReader
    public abstract class BaseCompositeReader<R extends IndexReader>
extends CompositeReader
    Base class for implementing CompositeReaders based on an array of sub-readers. The implementing class has to add code for correctly refcounting and closing the sub-readers.

    User code will most likely use MultiReader to build a composite reader on a set of sub-readers (like several DirectoryReaders).

    For efficiency, in this API documents are often referred to via document numbers, non-negative integers which each name a unique document in the index. These document numbers are ephemeral -- they may change as documents are added to and deleted from an index. Clients should thus not rely on a given document having the same number between sessions.

    NOTE: IndexReader instances are completely thread safe, meaning multiple threads can call any of its methods, concurrently. If your application requires external synchronization, you should not synchronize on the IndexReader instance; use your own (non-Lucene) objects instead.

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

    • Field Detail

      • subReadersSorter

        protected final Comparator<R extends IndexReader> subReadersSorter
        A comparator for sorting sub-readers

    • Constructor Detail

      • BaseCompositeReader

        protected BaseCompositeReader​(R[] subReaders,
                              Comparator<R> subReadersSorter)
                       throws IOException
        Constructs a BaseCompositeReader on the given subReaders.
        Parameters:
        subReaders - the wrapped sub-readers. This array is returned by getSequentialSubReaders() and used to resolve the correct subreader for docID-based methods. Please note: This array is not cloned and not protected for modification, the subclass is responsible to do this.
        subReadersSorter - – a comparator for sorting sub readers. If not null, this comparator is used to sort sub readers, before using the for resolving doc IDs.
        Throws:
        IOException

    • Method Detail

      • getTermVectors

        public final 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

      • termVectors

        public final TermVectors termVectors()
                              throws IOException
        Description copied from class: IndexReader
        Returns a TermVectors reader for the term vectors of this index.

        This call never returns null, even if no term vectors were indexed. The returned instance should only be used by a single thread.

        Example: 

         TopDocs hits = searcher.search(query, 10);
 TermVectors termVectors = reader.termVectors();
 for (ScoreDoc hit : hits.scoreDocs) {
   Fields vector = termVectors.get(hit.doc);
 }
        Specified by:
        termVectors in class IndexReader
        Throws:
        IOException - If there is a low-level IO error

      • numDocs

        public final 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 final 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

      • storedFields

        public final StoredFields storedFields()
                                throws IOException
        Description copied from class: IndexReader
        Returns a StoredFields reader for the stored fields of this index.

        This call never returns null, even if no stored fields were indexed. The returned instance should only be used by a single thread.

        Example: 

         TopDocs hits = searcher.search(query, 10);
 StoredFields storedFields = reader.storedFields();
 for (ScoreDoc hit : hits.scoreDocs) {
   Document doc = storedFields.document(hit.doc);
 }
        Specified by:
        storedFields in class IndexReader
        Throws:
        IOException - If there is a low-level IO error

      • docFreq

        public final int docFreq​(Term term)
                  throws IOException
        Description copied from class: IndexReader
        Returns the number of documents containing the term. This method returns 0 if the term or field does not exists. This method does not take into account deleted documents that have not yet been merged away.
        Specified by:
        docFreq in class IndexReader
        Throws:
        IOException
        See Also:
        TermsEnum.docFreq()

      • totalTermFreq

        public final long totalTermFreq​(Term term)
                         throws IOException
        Description copied from class: IndexReader
        Returns the total number of occurrences of term across all documents (the sum of the freq() for each doc that has this term). Note that, like other term measures, this measure does not take deleted documents into account.
        Specified by:
        totalTermFreq in class IndexReader
        Throws:
        IOException

      • getDocCount

        public final int getDocCount​(String field)
                      throws IOException
        Description copied from class: IndexReader
        Returns the number of documents that have at least one term for this field. Note that, just like other term measures, this measure does not take deleted documents into account.
        Specified by:
        getDocCount in class IndexReader
        Throws:
        IOException
        See Also:
        Terms.getDocCount()

      • readerIndex

        protected final int readerIndex​(int docID)
        Helper method for subclasses to get the corresponding reader for a doc ID

      • readerBase

        protected final int readerBase​(int readerIndex)
        Helper method for subclasses to get the docBase of the given sub-reader index.