Package org.apache.lucene.queries.spans

# Class FieldMaskingSpanQuery

java.lang.Object
org.apache.lucene.search.Query
org.apache.lucene.queries.spans.SpanQuery
org.apache.lucene.queries.spans.FieldMaskingSpanQuery

public final 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 Summary

  Constructors
  Constructor
  Description
  `FieldMaskingSpanQuery(SpanQuery maskedQuery, String maskedField)`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `SpanWeight`
  `createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost)`
  `boolean`
  `equals(Object other)`
  `String`
  `getField()`
  Returns the name of the field matched by this query.
  `SpanQuery`
  `getMaskedQuery()`
  `int`
  `hashCode()`
  `Query`
  `rewrite(IndexSearcher indexSearcher)`
  `String`
  `toString(String field)`
  `void`
  `visit(QueryVisitor visitor)`

  ### Methods inherited from class org.apache.lucene.queries.spans.SpanQuery

  `getTermStates, getTermStates`

  ### Methods inherited from class org.apache.lucene.search.Query

  `classHash, sameClassAs, toString`

  ### Methods inherited from class java.lang.Object

  `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### FieldMaskingSpanQuery

    public FieldMaskingSpanQuery(SpanQuery maskedQuery, String maskedField)

- ## Method Details

  - ### getField

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

  - ### getMaskedQuery

    public SpanQuery getMaskedQuery()

  - ### createWeight

    public SpanWeight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) throws IOException
    Specified by:
      `createWeight` in class `SpanQuery`
    Throws:
      `IOException`

  - ### rewrite

    public Query rewrite(IndexSearcher indexSearcher) throws IOException
    Overrides:
      `rewrite` in class `Query`
    Throws:
      `IOException`

  - ### visit

    public void visit(QueryVisitor visitor)
    Specified by:
      `visit` in class `Query`

  - ### toString

    public String toString(String field)
    Specified by:
      `toString` in class `Query`

  - ### equals

    public boolean equals(Object other)
    Specified by:
      `equals` in class `Query`

  - ### hashCode

    public int hashCode()
    Specified by:
      `hashCode` in class `Query`