Package org.apache.lucene.search
Class DisjunctionMaxQuery
- java.lang.Object
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- org.apache.lucene.search.Query
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- org.apache.lucene.search.DisjunctionMaxQuery
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- All Implemented Interfaces:
java.lang.Iterable<Query>
public final class DisjunctionMaxQuery extends Query implements java.lang.Iterable<Query>
A query that generates the union of documents produced by its subqueries, and that scores each document with the maximum score for that document as produced by any subquery, plus a tie breaking increment for any additional matching subqueries. This is useful when searching for a word in multiple fields with different boost factors (so that the fields cannot be combined equivalently into a single search field). We want the primary score to be the one associated with the highest boost, not the sum of the field scores (as BooleanQuery would give). If the query is "albino elephant" this ensures that "albino" matching one field and "elephant" matching another gets a higher score than "albino" matching both fields. To get this result, use both BooleanQuery and DisjunctionMaxQuery: for each term a DisjunctionMaxQuery searches for it in each field, while the set of these DisjunctionMaxQuery's is combined into a BooleanQuery. The tie breaker capability allows results that include the same term in multiple fields to be judged better than results that include this term in only the best of those multiple fields, without confusing this with the better case of two different terms in the multiple fields.
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Nested Class Summary
Nested Classes Modifier and Type Class Description protected class
DisjunctionMaxQuery.DisjunctionMaxWeight
Expert: the Weight for DisjunctionMaxQuery, used to normalize, score and explain these queries.
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Field Summary
Fields Modifier and Type Field Description private Query[]
disjuncts
private float
tieBreakerMultiplier
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Constructor Summary
Constructors Constructor Description DisjunctionMaxQuery(java.util.Collection<Query> disjuncts, float tieBreakerMultiplier)
Creates a new DisjunctionMaxQuery
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description Weight
createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost)
Create the Weight used to score usboolean
equals(java.lang.Object other)
Return true iff we represent the same query as oprivate boolean
equalsTo(DisjunctionMaxQuery other)
java.util.List<Query>
getDisjuncts()
float
getTieBreakerMultiplier()
int
hashCode()
Compute a hash code for hashing usjava.util.Iterator<Query>
iterator()
Query
rewrite(IndexReader reader)
Optimize our representation and our subqueries representationsjava.lang.String
toString(java.lang.String field)
Prettyprint us.void
visit(QueryVisitor visitor)
Recurse through the query tree, visiting any child queries-
Methods inherited from class org.apache.lucene.search.Query
classHash, sameClassAs, toString
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Field Detail
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disjuncts
private final Query[] disjuncts
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tieBreakerMultiplier
private final float tieBreakerMultiplier
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Constructor Detail
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DisjunctionMaxQuery
public DisjunctionMaxQuery(java.util.Collection<Query> disjuncts, float tieBreakerMultiplier)
Creates a new DisjunctionMaxQuery- Parameters:
disjuncts
- aCollection<Query>
of all the disjuncts to addtieBreakerMultiplier
- the score of each non-maximum disjunct for a document is multiplied by this weight and added into the final score. If non-zero, the value should be small, on the order of 0.1, which says that 10 occurrences of word in a lower-scored field that is also in a higher scored field is just as good as a unique word in the lower scored field (i.e., one that is not in any higher scored field.
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Method Detail
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iterator
public java.util.Iterator<Query> iterator()
- Specified by:
iterator
in interfacejava.lang.Iterable<Query>
- Returns:
- An
Iterator<Query>
over the disjuncts
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getDisjuncts
public java.util.List<Query> getDisjuncts()
- Returns:
- the disjuncts.
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getTieBreakerMultiplier
public float getTieBreakerMultiplier()
- Returns:
- tie breaker value for multiple matches.
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createWeight
public Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float boost) throws java.io.IOException
Create the Weight used to score us- Overrides:
createWeight
in classQuery
scoreMode
- How the produced scorers will be consumed.boost
- The boost that is propagated by the parent queries.- Throws:
java.io.IOException
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rewrite
public Query rewrite(IndexReader reader) throws java.io.IOException
Optimize our representation and our subqueries representations
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visit
public void visit(QueryVisitor visitor)
Description copied from class:Query
Recurse through the query tree, visiting any child queries
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toString
public java.lang.String toString(java.lang.String field)
Prettyprint us.
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equals
public boolean equals(java.lang.Object other)
Return true iff we represent the same query as o- Specified by:
equals
in classQuery
- Parameters:
other
- another object- Returns:
- true iff o is a DisjunctionMaxQuery with the same boost and the same subqueries, in the same order, as us
- See Also:
Query.sameClassAs(Object)
,Query.classHash()
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equalsTo
private boolean equalsTo(DisjunctionMaxQuery other)
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hashCode
public int hashCode()
Compute a hash code for hashing us- Specified by:
hashCode
in classQuery
- Returns:
- the hash code
- See Also:
Query.equals(Object)
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