DisjunctionMaxQuery (Lucene 2.9.4 API)

java.lang.Object
- org.apache.lucene.search.Query
- - org.apache.lucene.search.DisjunctionMaxQuery

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable
```
public class DisjunctionMaxQuery
extends 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.

See Also:

Serialized Form

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`protected class`	`DisjunctionMaxQuery.DisjunctionMaxWeight` Expert: the Weight for DisjunctionMaxQuery, used to normalize, score and explain these queries.

Constructor Summary

Constructors
Constructor and Description
`DisjunctionMaxQuery(java.util.Collection disjuncts, float tieBreakerMultiplier)` Creates a new DisjunctionMaxQuery
`DisjunctionMaxQuery(float tieBreakerMultiplier)` Creates a new empty DisjunctionMaxQuery.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`add(java.util.Collection disjuncts)` Add a collection of disjuncts to this disjunction via Iterable
`void`	`add(Query query)` Add a subquery to this disjunction
`java.lang.Object`	`clone()` Create a shallow copy of us -- used in rewriting if necessary
`Weight`	`createWeight(Searcher searcher)` Expert: Constructs an appropriate Weight implementation for this query.
`boolean`	`equals(java.lang.Object o)` Return true iff we represent the same query as o
`void`	`extractTerms(java.util.Set terms)` Expert: adds all terms occurring in this query to the terms set.
`int`	`hashCode()` Compute a hash code for hashing us
`java.util.Iterator`	`iterator()` An Iterator over the disjuncts
`Query`	`rewrite(IndexReader reader)` Optimize our representation and our subqueries representations
`java.lang.String`	`toString(java.lang.String field)` Prettyprint us.

Methods inherited from class org.apache.lucene.search.Query
combine, getBoost, getSimilarity, mergeBooleanQueries, setBoost, toString, weight

Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - DisjunctionMaxQuery
```
public DisjunctionMaxQuery(float tieBreakerMultiplier)
```
    Creates a new empty DisjunctionMaxQuery. Use add() to add the subqueries.
    
    Parameters:
    
    tieBreakerMultiplier - 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.
  - DisjunctionMaxQuery
```
public DisjunctionMaxQuery(java.util.Collection disjuncts,
                           float tieBreakerMultiplier)
```
    Creates a new DisjunctionMaxQuery
    
    Parameters:
    
    disjuncts - a Collection of all the disjuncts to add
    
    tieBreakerMultiplier - the weight to give to each matching non-maximum disjunct
- Method Detail
  - add
```
public void add(Query query)
```
    Add a subquery to this disjunction
    
    Parameters:
    
    query - the disjunct added
  - add
```
public void add(java.util.Collection disjuncts)
```
    Add a collection of disjuncts to this disjunction via Iterable
  - iterator
```
public java.util.Iterator iterator()
```
    An Iterator over the disjuncts
  - createWeight
```
public Weight createWeight(Searcher searcher)
                    throws java.io.IOException
```
    Description copied from class: Query
    
    Expert: Constructs an appropriate Weight implementation for this query.
    Only implemented by primitive queries, which re-write to themselves.
    
    Overrides:
    
    createWeight in class Query
    
    Throws:
    
    java.io.IOException
  - rewrite
```
public Query rewrite(IndexReader reader)
              throws java.io.IOException
```
    Optimize our representation and our subqueries representations
    
    Overrides:
    
    rewrite in class Query
    
    Parameters:
    
    reader - the IndexReader we query
    
    Returns:
    
    an optimized copy of us (which may not be a copy if there is nothing to optimize)
    
    Throws:
    
    java.io.IOException
  - clone
```
public java.lang.Object clone()
```
    Create a shallow copy of us -- used in rewriting if necessary
    
    Overrides:
    
    clone in class Query
    
    Returns:
    
    a copy of us (but reuse, don't copy, our subqueries)
  - extractTerms
```
public void extractTerms(java.util.Set terms)
```
    Description copied from class: Query
    
    Expert: adds all terms occurring in this query to the terms set. Only works if this query is in its rewritten form.
    
    Overrides:
    
    extractTerms in class Query
  - toString
```
public java.lang.String toString(java.lang.String field)
```
    Prettyprint us.
    
    Specified by:
    
    toString in class Query
    
    Parameters:
    
    field - the field to which we are applied
    
    Returns:
    
    a string that shows what we do, of the form "(disjunct1 | disjunct2 | ... | disjunctn)^boost"
  - equals
```
public boolean equals(java.lang.Object o)
```
    Return true iff we represent the same query as o
    
    Overrides:
    
    equals in class Query
    
    Parameters:
    
    o - another object
    
    Returns:
    
    true iff o is a DisjunctionMaxQuery with the same boost and the same subqueries, in the same order, as us
  - hashCode
```
public int hashCode()
```
    Compute a hash code for hashing us
    
    Overrides:
    
    hashCode in class Query
    
    Returns:
    
    the hash code

Class DisjunctionMaxQuery

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class org.apache.lucene.search.Query

Methods inherited from class java.lang.Object

Constructor Detail

DisjunctionMaxQuery

DisjunctionMaxQuery

Method Detail

add

add

iterator

createWeight

rewrite

clone

extractTerms

toString

equals

hashCode