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
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.
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptioncreateWeight
(IndexSearcher searcher, ScoreMode scoreMode, float boost) boolean
getField()
Returns the name of the field matched by this query.int
hashCode()
rewrite
(IndexSearcher indexSearcher) 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, rewrite, sameClassAs, toString
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Constructor Details
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FieldMaskingSpanQuery
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Method Details
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getField
Description copied from class:SpanQuery
Returns the name of the field matched by this query. -
getMaskedQuery
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createWeight
public SpanWeight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) throws IOException - Specified by:
createWeight
in classSpanQuery
- Throws:
IOException
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rewrite
- Overrides:
rewrite
in classQuery
- Throws:
IOException
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visit
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toString
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equals
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hashCode
public int hashCode()
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