| java.lang.Object
 org.apache.lucene.search.Query
org.apache.lucene.search.DisjunctionMaxQuery
| DisjunctionMaxQuery | | public class DisjunctionMaxQuery extends Query (Code) | | 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.
author:
Chuck Williams |
| DisjunctionMaxQuery | | public DisjunctionMaxQuery(float tieBreakerMultiplier)(Code) | | Creates a new empty DisjunctionMaxQuery. Use add() to add the subqueries.
Parameters:
tieBreakerMultiplier - this score of each non-maximum disjunct for a document is multiplied by this weightand added into the final score. If non-zero, the value should be small, on the order of 0.1, which says that10 occurrences of word in a lower-scored field that is also in a higher scored field is just as good as a uniqueword in the lower scored field (i.e., one that is not in any higher scored field. |
| DisjunctionMaxQuery | | public DisjunctionMaxQuery(Collection disjuncts, float tieBreakerMultiplier)(Code) | | Creates a new DisjunctionMaxQuery
Parameters:
disjuncts - a Collection of all the disjuncts to add
Parameters:
tieBreakerMultiplier - the weight to give to each matching non-maximum disjunct |
| add | | public void add(Query query)(Code) | | Add a subquery to this disjunction
Parameters:
query - the disjunct added |
| add | | public void add(Collection disjuncts)(Code) | | Add a collection of disjuncts to this disjunction
via Iterable
|
| clone | | public Object clone()(Code) | | Create a shallow copy of us -- used in rewriting if necessary
a copy of us (but reuse, don't copy, our subqueries) |
| equals | | public boolean equals(Object o)(Code) | | Return true iff we represent the same query as o
Parameters:
o - another object true iff o is a DisjunctionMaxQuery with the same boost and the same subqueries, in the same order, as us |
| extractTerms | | public void extractTerms(Set terms)(Code) | | |
| hashCode | | public int hashCode()(Code) | | Compute a hash code for hashing us
the hash code |
| iterator | | public Iterator iterator()(Code) | | An Iterator over the disjuncts
|
| rewrite | | public Query rewrite(IndexReader reader) throws IOException(Code) | | Optimize our representation and our subqueries representations
Parameters:
reader - the IndexReader we query an optimized copy of us (which may not be a copy if there is nothing to optimize) |
| toString | | public String toString(String field)(Code) | | Prettyprint us.
Parameters:
field - the field to which we are applied a string that shows what we do, of the form "(disjunct1 | disjunct2 | ... | disjunctn)^boost" |
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