Package org.apache.lucene.search.join

Class ToParentBlockJoinQuery

  • All Implemented Interfaces:
    Serializable, Cloneable
    public class ToParentBlockJoinQuery
extends org.apache.lucene.search.Query
    This query requires that you index children and parent docs as a single block, using the IndexWriter.addDocuments(java.util.Collection<org.apache.lucene.document.Document>) or IndexWriter.updateDocuments(org.apache.lucene.index.Term, java.util.Collection<org.apache.lucene.document.Document>) API. In each block, the child documents must appear first, ending with the parent document. At search time you provide a Filter identifying the parents, however this Filter must provide an FixedBitSet per sub-reader.

    WARNING: to create the parents filter, always use RawTermFilter (so that the filter includes deleted docs), wrapped with CachingWrapperFilter (so that the returned bit set per reader is a FixedBitSet), specifying DeletesMode.IGNORE (so that on reopen, the filter still includes deleted docs). Failure to do this can result in completely wrong documents being returned! For example: 

       Filter parents = new CachingWrapperFilter(
                          new RawTermFilter(new Term("parent", "yes")),
                          CachingWrapperFilter.DeletesMode.IGNORE);

    Once the block index is built, use this query to wrap any sub-query matching only child docs and join matches in that child document space up to the parent document space. You can then use this Query as a clause with other queries in the parent document space.

    See ToChildBlockJoinQuery if you need to join in the reverse order.

    The child documents must be orthogonal to the parent documents: the wrapped child query must never return a parent document.

    If you'd like to retrieve TopGroups for the resulting query, use the ToParentBlockJoinCollector. Note that this is not necessary, ie, if you simply want to collect the parent documents and don't need to see which child documents matched under that parent, then you can use any collector.

    NOTE: If the overall query contains parent-only matches, for example you OR a parent-only query with a joined child-only query, then the resulting collected documents will be correct, however the TopGroups you get from ToParentBlockJoinCollector will not contain every child for parents that had matched.

    See org.apache.lucene.search.join for an overview.

    See Also:
    Serialized Form
    WARNING: This API is experimental and might change in incompatible ways in the next release.

    • Constructor Detail

      • ToParentBlockJoinQuery

        public ToParentBlockJoinQuery​(org.apache.lucene.search.Query childQuery,
                              org.apache.lucene.search.Filter parentsFilter,
                              ToParentBlockJoinQuery.ScoreMode scoreMode)
        Create a ToParentBlockJoinQuery.
        Parameters:
        childQuery - Query matching child documents.
        parentsFilter - Filter (must produce FixedBitSet per-seegment) identifying the parent documents.
        scoreMode - How to aggregate multiple child scores into a single parent score.

    • Method Detail

      • createWeight

        public org.apache.lucene.search.Weight createWeight​(org.apache.lucene.search.Searcher searcher)
                                             throws IOException
        Overrides:
        createWeight in class org.apache.lucene.search.Query
        Throws:
        IOException

      • extractTerms

        public void extractTerms​(Set<org.apache.lucene.index.Term> terms)
        Overrides:
        extractTerms in class org.apache.lucene.search.Query

      • rewrite

        public org.apache.lucene.search.Query rewrite​(org.apache.lucene.index.IndexReader reader)
                                       throws IOException
        Overrides:
        rewrite in class org.apache.lucene.search.Query
        Throws:
        IOException

      • toString

        public String toString​(String field)
        Specified by:
        toString in class org.apache.lucene.search.Query

      • equals

        public boolean equals​(Object _other)
        Overrides:
        equals in class org.apache.lucene.search.Query

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class org.apache.lucene.search.Query

      • clone

        public Object clone()
        Overrides:
        clone in class org.apache.lucene.search.Query