org.apache.lucene.search.join

Class ToParentBlockJoinQuery



  • public class ToParentBlockJoinQuery
    extends Query
    This query requires that you index children and parent docs as a single block, using the IndexWriter.addDocuments() or IndexWriter.updateDocuments() 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 BitSet per sub-reader.

    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.

    • Constructor Detail

      • ToParentBlockJoinQuery

        public ToParentBlockJoinQuery(Query childQuery,
                                      BitSetProducer parentsFilter,
                                      ScoreMode scoreMode)
        Create a ToParentBlockJoinQuery.
        Parameters:
        childQuery - Query matching child documents.
        parentsFilter - Filter identifying the parent documents.
        scoreMode - How to aggregate multiple child scores into a single parent score.
    • Method Detail

      • rewrite

        public Query rewrite(IndexReader reader)
                      throws IOException
        Description copied from class: Query
        Expert: called to re-write queries into primitive queries. For example, a PrefixQuery will be rewritten into a BooleanQuery that consists of TermQuerys.
        Overrides:
        rewrite in class Query
        Throws:
        IOException
      • toString

        public String toString(String field)
        Description copied from class: Query
        Prints a query to a string, with field assumed to be the default field and omitted.
        Specified by:
        toString in class Query
      • equals

        public boolean equals(Object other)
        Description copied from class: Query
        Override and implement query instance equivalence properly in a subclass. This is required so that QueryCache works properly. Typically a query will be equal to another only if it's an instance of the same class and its document-filtering properties are identical that other instance. Utility methods are provided for certain repetitive code.
        Specified by:
        equals in class Query
        See Also:
        Query.sameClassAs(Object), Query.classHash()