romseygeek commented on a change in pull request #581: LUCENE-3041: QueryVisitor URL: https://github.com/apache/lucene-solr/pull/581#discussion_r261135733
########## File path: lucene/core/src/java/org/apache/lucene/search/QueryVisitor.java ########## @@ -0,0 +1,80 @@ +/* + * 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.Set; + +import org.apache.lucene.index.Term; + +/** + * Allows recursion through a query tree + * + * @see Query#visit(QueryVisitor) + */ +public abstract class QueryVisitor { + + /** + * Called by leaf queries that match on a specific term + * + * @param query the leaf query + * @param term the term the query will match on + */ + public void consumesTerm(Query query, Term term) { } + + /** + * Called by leaf queries that do not match on terms + * @param query the query + */ + public void visitLeaf(Query query) { } + + /** + * 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; Review comment: > so I take it that such usage will become production code in the future and not only test code Yes - I have plans for luwak :) . I've added some test code to show how the `parent` argument can be used as well. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org
