Class FieldMaskingSpanQuery

  • All Implemented Interfaces:

    public class FieldMaskingSpanQuery
    extends SpanQuery

    Wrapper to allow SpanQuery objects participate in composite single-field SpanQueries by 'lying' about their search field. That is, the masked SpanQuery will function as normal, but SpanQuery.getField() simply hands back the value supplied in this class's constructor.

    This can be used to support Queries like SpanNearQuery or SpanOrQuery across different fields, which is not ordinarily permitted.

    This can be useful for denormalized relational data: for example, when indexing a document with conceptually many 'children':

      teacherid: 1
      studentfirstname: james
      studentsurname: jones
      teacherid: 2
      studenfirstname: james
      studentsurname: smith
      studentfirstname: sally
      studentsurname: jones

    a SpanNearQuery with a slop of 0 can be applied across two SpanTermQuery objects as follows:

        SpanQuery q1  = new SpanTermQuery(new Term("studentfirstname", "james"));
        SpanQuery q2  = new SpanTermQuery(new Term("studentsurname", "jones"));
        SpanQuery q2m = new FieldMaskingSpanQuery(q2, "studentfirstname");
        Query q = new SpanNearQuery(new SpanQuery[]{q1, q2m}, -1, false);
    to search for 'studentfirstname:james studentsurname:jones' and find teacherid 1 without matching teacherid 2 (which has a 'james' in position 0 and 'jones' in position 1).

    Note: as getField() returns the masked field, scoring will be done using the Similarity and collection statistics of the field name supplied, but with the term statistics of the real field. This may lead to exceptions, poor performance, and unexpected scoring behaviour.

    • Constructor Detail

      • FieldMaskingSpanQuery

        public FieldMaskingSpanQuery​(SpanQuery maskedQuery,
                                     java.lang.String maskedField)
    • Method Detail

      • getField

        public java.lang.String getField()
        Description copied from class: SpanQuery
        Returns the name of the field matched by this query.

        Note that this may return null if the query matches no terms.

        Specified by:
        getField in class SpanQuery
      • getMaskedQuery

        public SpanQuery getMaskedQuery()
      • getSpans

        public Spans getSpans​(AtomicReaderContext context,
                              Bits acceptDocs,
                              java.util.Map<Term,​TermContext> termContexts)
        Description copied from class: SpanQuery
        Expert: Returns the matches for this query in an index. Used internally to search for spans.
        Specified by:
        getSpans in class SpanQuery
      • extractTerms

        public void extractTerms​(java.util.Set<Term> terms)
        Description copied from class: Query
        Expert: adds all terms occurring in this query to the terms set. Only works if this query is in its rewritten form.
        extractTerms in class Query
      • createWeight

        public Weight createWeight​(IndexSearcher searcher)
        Description copied from class: Query
        Expert: Constructs an appropriate Weight implementation for this query.

        Only implemented by primitive queries, which re-write to themselves.

        createWeight in class SpanQuery
      • rewrite

        public Query rewrite​(IndexReader reader)
        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.
        rewrite in class Query
      • toString

        public java.lang.String toString​(java.lang.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​(java.lang.Object o)
        equals in class Query
      • hashCode

        public int hashCode()
        hashCode in class Query