| /* |
| * 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. |
| */ |
| |
| package org.apache.lucene.search; |
| |
| import java.util.Arrays; |
| import java.util.Set; |
| import java.util.function.Supplier; |
| |
| import org.apache.lucene.index.Term; |
| import org.apache.lucene.util.automaton.ByteRunAutomaton; |
| |
| /** |
| * Allows recursion through a query tree |
| * |
| * @see Query#visit(QueryVisitor) |
| */ |
| public abstract class QueryVisitor { |
| |
| /** |
| * Called by leaf queries that match on specific terms |
| * |
| * @param query the leaf query |
| * @param terms the terms the query will match on |
| */ |
| public void consumeTerms(Query query, Term... terms) { } |
| |
| /** |
| * Called by leaf queries that match on a class of terms |
| * |
| * @param query the leaf query |
| * @param field the field queried against |
| * @param automaton a supplier for an automaton defining which terms match |
| * |
| * @lucene.experimental |
| */ |
| public void consumeTermsMatching(Query query, String field, Supplier<ByteRunAutomaton> automaton) { |
| visitLeaf(query); // default impl for backward compatibility |
| } |
| |
| /** |
| * Called by leaf queries that do not match on terms |
| * @param query the query |
| */ |
| public void visitLeaf(Query query) { } |
| |
| /** |
| * Whether or not terms from this field are of interest to the visitor |
| * |
| * Implement this to avoid collecting terms from heavy queries such as {@link TermInSetQuery} |
| * that are not running on fields of interest |
| */ |
| public boolean acceptField(String field) { |
| return true; |
| } |
| |
| /** |
| * Pulls a visitor instance for visiting child clauses of a query |
| * |
| * The default implementation returns {@code this}, unless {@code occur} is equal |
| * to {@link BooleanClause.Occur#MUST_NOT} in which case it returns |
| * {@link #EMPTY_VISITOR} |
| * |
| * @param occur the relationship between the parent and its children |
| * @param parent the query visited |
| */ |
| public QueryVisitor getSubVisitor(BooleanClause.Occur occur, Query parent) { |
| if (occur == BooleanClause.Occur.MUST_NOT) { |
| return EMPTY_VISITOR; |
| } |
| return this; |
| } |
| |
| /** |
| * Builds a {@code QueryVisitor} instance that collects all terms that may match a query |
| * @param termSet a {@code Set} to add collected terms to |
| */ |
| public static QueryVisitor termCollector(Set<Term> termSet) { |
| return new QueryVisitor() { |
| @Override |
| public void consumeTerms(Query query, Term... terms) { |
| termSet.addAll(Arrays.asList(terms)); |
| } |
| }; |
| } |
| |
| /** |
| * A QueryVisitor implementation that does nothing |
| */ |
| public static final QueryVisitor EMPTY_VISITOR = new QueryVisitor() {}; |
| |
| } |