BoostingQuerypublic 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This code was originally made available here: [WWW] http://marc.theaimsgroup.com/?l=lucene-user&m=108058407130459&w=2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/jakarta-lucene/CommunityContributions |
| Fields Summary |
|---|
| private float | boost | | private Query | match | | private Query | context |
| Constructors Summary |
|---|
public BoostingQuery(Query match, Query context, float boost)
this.match = match;
this.context = (Query)context.clone(); // clone before boost
this.boost = boost;
context.setBoost(0.0f); // ignore context-only matches
|
| Methods Summary |
|---|
| public org.apache.lucene.search.Query | rewrite(org.apache.lucene.index.IndexReader reader)
BooleanQuery result = new BooleanQuery() {
public Similarity getSimilarity(Searcher searcher) {
return new DefaultSimilarity() {
public float coord(int overlap, int max) {
switch (overlap) {
case 1: // matched only one clause
return 1.0f; // use the score as-is
case 2: // matched both clauses
return boost; // multiply by boost
default:
return 0.0f;
}
}
};
}
};
result.add(match, BooleanClause.Occur.MUST);
result.add(context, BooleanClause.Occur.SHOULD);
return result;
| | public java.lang.String | toString(java.lang.String field)
return match.toString(field) + "/" + context.toString(field);
|
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