Package org.apache.lucene.search

Class AutomatonQuery

java.lang.Object

org.apache.lucene.search.Query

org.apache.lucene.search.MultiTermQuery

org.apache.lucene.search.AutomatonQuery

All Implemented Interfaces:

Cloneable

Direct Known Subclasses:

RegexpQuery, WildcardQuery

public class AutomatonQuery
extends MultiTermQuery

A Query that will match terms against a finite-state machine.

This query will match documents that contain terms accepted by a given finite-state machine. The automaton can be constructed with the org.apache.lucene.util.automaton API. Alternatively, it can be created from a regular expression with RegexpQuery or from the standard Lucene wildcard syntax with WildcardQuery.

When the query is executed, it will create an equivalent DFA of the finite-state machine, and will enumerate the term dictionary in an intelligent way to reduce the number of comparisons. For example: the regular expression of [dl]og? will make approximately four comparisons: do, dog, lo, and log.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.search.MultiTermQuery

MultiTermQuery.ConstantScoreAutoRewrite, MultiTermQuery.RewriteMethod, MultiTermQuery.TopTermsBoostOnlyBooleanQueryRewrite, MultiTermQuery.TopTermsScoringBooleanQueryRewrite

Field Summary

Fields

Modifier and Type	Field	Description
protected Automaton	automaton	the automaton to match index terms against
protected CompiledAutomaton	compiled
protected Term	term	term containing the field, and possibly some pattern structure

Fields inherited from class org.apache.lucene.search.MultiTermQuery

CONSTANT_SCORE_AUTO_REWRITE_DEFAULT, CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE, CONSTANT_SCORE_FILTER_REWRITE, field, rewriteMethod, SCORING_BOOLEAN_QUERY_REWRITE

Constructor Summary

Constructors

Constructor	Description
AutomatonQuery(Term term, Automaton automaton)	Create a new AutomatonQuery from an Automaton.

Method Summary

Modifier and Type	Method	Description
boolean	equals(Object obj)
Automaton	getAutomaton()	Returns the automaton used to create this query
protected TermsEnum	getTermsEnum(Terms terms, AttributeSource atts)	Construct the enumeration to be used, expanding the pattern term.
int	hashCode()
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.MultiTermQuery

getField, getRewriteMethod, getTermsEnum, rewrite, setRewriteMethod

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

clone, createWeight, extractTerms, getBoost, setBoost, toString

Methods inherited from class java.lang.Object

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

Field Detail

automaton

protected final Automaton automaton

the automaton to match index terms against

compiled

protected final CompiledAutomaton compiled

term

protected final Term term

term containing the field, and possibly some pattern structure

Constructor Detail

AutomatonQuery

public AutomatonQuery(Term term,
                      Automaton automaton)

Create a new AutomatonQuery from an Automaton.

Parameters:

term - Term containing field and possibly some pattern structure. The term text is ignored.

automaton - Automaton to run, terms that are accepted are considered a match.

Method Detail

getTermsEnum

protected TermsEnum getTermsEnum(Terms terms,
                                 AttributeSource atts)
                          throws IOException

Description copied from class: MultiTermQuery

Construct the enumeration to be used, expanding the pattern term. This method should only be called if the field exists (ie, implementations can assume the field does exist). This method should not return null (should instead return TermsEnum.EMPTY if no terms match). The TermsEnum must already be positioned to the first matching term. The given AttributeSource is passed by the MultiTermQuery.RewriteMethod to provide attributes, the rewrite method uses to inform about e.g. maximum competitive boosts. This is currently only used by TopTermsRewrite

Specified by:

getTermsEnum in class MultiTermQuery

Throws:

IOException

hashCode

public int hashCode()

Overrides:

hashCode in class MultiTermQuery

equals

public boolean equals(Object obj)

Overrides:

equals in class MultiTermQuery

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

getAutomaton

public Automaton getAutomaton()

Returns the automaton used to create this query