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`