Package org.apache.lucene.queries.spans
Class FieldMaskingSpanQuery
- java.lang.Object
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- org.apache.lucene.search.Query
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- org.apache.lucene.queries.spans.SpanQuery
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- org.apache.lucene.queries.spans.FieldMaskingSpanQuery
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public final class FieldMaskingSpanQuery extends SpanQuery
Wrapper to allowSpanQueryobjects participate in composite single-field SpanQueries by 'lying' about their search field. That is, the masked SpanQuery will function as normal, butSpanQuery.getField()simply hands back the value supplied in this class's constructor.This can be used to support Queries like
SpanNearQueryorSpanOrQueryacross 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
SpanTermQueryobjects 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 Constructor Description FieldMaskingSpanQuery(SpanQuery maskedQuery, String maskedField)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description SpanWeightcreateWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost)booleanequals(Object other)StringgetField()Returns the name of the field matched by this query.SpanQuerygetMaskedQuery()inthashCode()Queryrewrite(IndexSearcher indexSearcher)StringtoString(String field)voidvisit(QueryVisitor visitor)-
Methods inherited from class org.apache.lucene.queries.spans.SpanQuery
getTermStates, getTermStates
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Methods inherited from class org.apache.lucene.search.Query
classHash, rewrite, sameClassAs, toString
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Method Detail
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getField
public String getField()
Description copied from class:SpanQueryReturns the name of the field matched by this query.
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getMaskedQuery
public SpanQuery getMaskedQuery()
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createWeight
public SpanWeight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) throws IOException
- Specified by:
createWeightin classSpanQuery- Throws:
IOException
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rewrite
public Query rewrite(IndexSearcher indexSearcher) throws IOException
- Overrides:
rewritein classQuery- Throws:
IOException
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visit
public void visit(QueryVisitor visitor)
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