package org.apache.lucene.search;
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.IOException;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermsEnum;
import org.apache.lucene.index.MultiFields;
import org.apache.lucene.util.ToStringUtils;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.automaton.Automaton;
import org.apache.lucene.util.automaton.ByteRunAutomaton;
import org.apache.lucene.util.automaton.BasicAutomata;
import org.apache.lucene.util.automaton.BasicOperations;
import org.apache.lucene.util.automaton.MinimizationOperations;
import org.apache.lucene.util.automaton.SpecialOperations;
/**
* A {@link Query} that will match terms against a finite-state machine.
* <p>
* This query will match documents that contain terms accepted by a given
* finite-state machine. The automaton can be constructed with the
* {@link org.apache.lucene.util.automaton} API. Alternatively, it can be
* created from a regular expression with {@link RegexpQuery} or from
* the standard Lucene wildcard syntax with {@link WildcardQuery}.
* </p>
* <p>
* When the query is executed, it will create an equivalent minimal 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 <code>[dl]og?</code> will make approximately four comparisons:
* do, dog, lo, and log.
* </p>
* @lucene.experimental
*/
public class AutomatonQuery extends MultiTermQuery {
/** the automaton to match index terms against */
protected final Automaton automaton;
/** term containing the field, and possibly some pattern structure */
protected final Term term;
transient ByteRunAutomaton runAutomaton;
transient boolean isFinite;
transient BytesRef commonSuffixRef;
/**
* Create a new AutomatonQuery from an {@link Automaton}.
*
* @param term Term containing field and possibly some pattern structure. The
* term text is ignored.
* @param automaton Automaton to run, terms that are accepted are considered a
* match.
*/
public AutomatonQuery(Term term, Automaton automaton) {
super(term.field());
this.term = term;
this.automaton = automaton;
MinimizationOperations.minimize(automaton);
}
private synchronized void compileAutomaton() {
// this method must be synchronized, as setting the three transient fields is not atomic:
if (runAutomaton == null) {
runAutomaton = new ByteRunAutomaton(automaton);
isFinite = SpecialOperations.isFinite(automaton);
commonSuffixRef = isFinite ? null : SpecialOperations.getCommonSuffixBytesRef(runAutomaton.getAutomaton());
}
}
@Override
protected TermsEnum getTermsEnum(IndexReader reader) throws IOException {
// matches nothing
if (BasicOperations.isEmpty(automaton)) {
return TermsEnum.EMPTY;
}
// matches all possible strings
if (BasicOperations.isTotal(automaton)) {
// NOTE: for now, MultiTermQuery enums terms at the
// MultiReader level, so we must use MultiFields here:
return MultiFields.getTerms(reader, getField()).iterator();
}
// matches a fixed string in singleton representation
String singleton = automaton.getSingleton();
if (singleton != null)
return new SingleTermsEnum(reader, term.createTerm(singleton));
// matches a fixed string in expanded representation
final String commonPrefix = SpecialOperations.getCommonPrefix(automaton);
if (commonPrefix.length() > 0) {
if (BasicOperations.sameLanguage(automaton, BasicAutomata.makeString(commonPrefix))) {
return new SingleTermsEnum(reader, term.createTerm(commonPrefix));
}
// matches a constant prefix
Automaton prefixAutomaton = BasicOperations.concatenate(BasicAutomata
.makeString(commonPrefix), BasicAutomata.makeAnyString());
if (BasicOperations.sameLanguage(automaton, prefixAutomaton)) {
return new PrefixTermsEnum(reader, term.createTerm(commonPrefix));
}
}
compileAutomaton();
return new AutomatonTermsEnum(runAutomaton, term.field(), reader, isFinite, commonSuffixRef);
}
@Override
public int hashCode() {
final int prime = 31;
int result = super.hashCode();
if (automaton != null) {
// we already minimized the automaton in the ctor, so
// this hash code will be the same for automata that
// are the same:
int automatonHashCode = automaton.getNumberOfStates() * 3 + automaton.getNumberOfTransitions() * 2;
if (automatonHashCode == 0) {
automatonHashCode = 1;
}
result = prime * result + automatonHashCode;
}
result = prime * result + ((term == null) ? 0 : term.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (!super.equals(obj))
return false;
if (getClass() != obj.getClass())
return false;
AutomatonQuery other = (AutomatonQuery) obj;
if (automaton == null) {
if (other.automaton != null)
return false;
} else if (!BasicOperations.sameLanguage(automaton, other.automaton))
return false;
if (term == null) {
if (other.term != null)
return false;
} else if (!term.equals(other.term))
return false;
return true;
}
@Override
public String toString(String field) {
StringBuilder buffer = new StringBuilder();
if (!term.field().equals(field)) {
buffer.append(term.field());
buffer.append(":");
}
buffer.append(getClass().getSimpleName());
buffer.append(" {");
buffer.append('\n');
buffer.append(automaton.toString());
buffer.append("}");
buffer.append(ToStringUtils.boost(getBoost()));
return buffer.toString();
}
}