org.apache.lucene.search

Class BlendedTermQuery

java.lang.Object

org.apache.lucene.search.Query

org.apache.lucene.search.BlendedTermQuery

public final class BlendedTermQuery
extends Query

A Query that blends index statistics across multiple terms. This is particularly useful when several terms should produce identical scores, regardless of their index statistics.

For instance imagine that you are resolving synonyms at search time, all terms should produce identical scores instead of the default behavior, which tends to give higher scores to rare terms.

An other useful use-case is cross-field search: imagine that you would like to search for john on two fields: first_name and last_name. You might not want to give a higher weight to matches on the field where john is rarer, in which case BlendedTermQuery would help as well.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	BlendedTermQuery.Builder A Builder for BlendedTermQuery.
static class	BlendedTermQuery.DisjunctionMaxRewrite A BlendedTermQuery.RewriteMethod that creates a DisjunctionMaxQuery out of the sub queries.
static class	BlendedTermQuery.RewriteMethod A BlendedTermQuery.RewriteMethod defines how queries for individual terms should be merged.

Field Summary

Fields

Modifier and Type	Field and Description
static BlendedTermQuery.RewriteMethod	BOOLEAN_REWRITE A BlendedTermQuery.RewriteMethod that adds all sub queries to a BooleanQuery which has coords disabled.
static BlendedTermQuery.RewriteMethod	DISJUNCTION_MAX_REWRITE BlendedTermQuery.DisjunctionMaxRewrite instance with a tie-breaker of 0.01.

Method Summary

Modifier and Type	Method and 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, with field assumed to be the default field and omitted.

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

createWeight, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

BOOLEAN_REWRITE

public static final BlendedTermQuery.RewriteMethod BOOLEAN_REWRITE

A BlendedTermQuery.RewriteMethod that adds all sub queries to a BooleanQuery which has coords disabled. This BlendedTermQuery.RewriteMethod is useful when matching on several fields is considered better than having a good match on a single field.

DISJUNCTION_MAX_REWRITE

public static final BlendedTermQuery.RewriteMethod DISJUNCTION_MAX_REWRITE

BlendedTermQuery.DisjunctionMaxRewrite instance with a tie-breaker of 0.01.

Method Detail

equals

public boolean equals(Object obj)

Overrides:

equals in class Query

hashCode

public int hashCode()

Overrides:

hashCode in class Query

toString

public String toString(String field)

Description copied from class: Query

Prints a query to a string, with field assumed to be the default field and omitted.

Specified by:

toString in class Query

rewrite

public final 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 class Query

Throws:

IOException