Package org.apache.lucene.search
Class BoostingQuery
- java.lang.Object
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- org.apache.lucene.search.Query
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- org.apache.lucene.search.BoostingQuery
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- All Implemented Interfaces:
Serializable
,Cloneable
public class BoostingQuery extends Query
The BoostingQuery class can be used to effectively demote results that match a given query. Unlike the "NOT" clause, this still selects documents that contain undesirable terms, but reduces their overall score: Query balancedQuery = new BoostingQuery(positiveQuery, negativeQuery, 0.01f); In this scenario the positiveQuery contains the mandatory, desirable criteria which is used to select all matching documents, and the negativeQuery contains the undesirable elements which are simply used to lessen the scores. Documents that match the negativeQuery have their score multiplied by the supplied "boost" parameter, so this should be less than 1 to achieve a demoting effect This code was originally made available here: [WWW] http://marc.theaimsgroup.com/?l=lucene-user&m=108058407130459&w=2 and is documented here: http://wiki.apache.org/lucene-java/CommunityContributions- See Also:
- Serialized Form
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Constructor Summary
Constructors Constructor Description BoostingQuery(Query match, Query context, float boost)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
equals(Object obj)
int
hashCode()
Query
rewrite(IndexReader reader)
Expert: called to re-write queries into primitive queries.String
toString(String field)
Prints a query to a string, withfield
assumed to be the default field and omitted.-
Methods inherited from class org.apache.lucene.search.Query
clone, combine, createWeight, extractTerms, getBoost, getSimilarity, mergeBooleanQueries, setBoost, toString, weight
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Method Detail
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rewrite
public Query rewrite(IndexReader reader) throws IOException
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.- Overrides:
rewrite
in classQuery
- Throws:
IOException
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toString
public String toString(String field)
Description copied from class:Query
Prints a query to a string, withfield
assumed to be the default field and omitted.The representation used is one that is supposed to be readable by
QueryParser
. However, there are the following limitations:- If the query was created by the parser, the printed representation may not be exactly what was parsed. For example, characters that need to be escaped will be represented without the required backslash.
- Some of the more complicated queries (e.g. span queries) don't have a representation that can be parsed by QueryParser.
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