silundong commented on code in PR #4392: URL: https://github.com/apache/calcite/pull/4392#discussion_r2103865329
########## core/src/main/java/org/apache/calcite/rel/rules/ConflictDetectionHelper.java: ########## @@ -0,0 +1,215 @@ +/* + * 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.calcite.rel.rules; + +import org.apache.calcite.rel.core.JoinRelType; + +import com.google.common.collect.ImmutableMap; + +import java.util.HashMap; +import java.util.List; +import java.util.Map; + +/** + * Conflict detection algorithm based on CD-C. More details are in paper: + * On the correct and complete enumeration of the core search space. + */ +public class ConflictDetectionHelper { + + private ConflictDetectionHelper() { + } + + private static final ImmutableMap<JoinRelType, Integer> INDEX_OF_TABLE = + ImmutableMap.<JoinRelType, Integer>builder() + .put(JoinRelType.INNER, 0).put(JoinRelType.SEMI, 1).put(JoinRelType.ANTI, 2) + .put(JoinRelType.LEFT, 3).put(JoinRelType.FULL, 4).build(); + + // TODO: when special attribute is null rejecting, left/full join is Review Comment: The associativity table given in the paper is shown in the figure below. Assuming that o_a and o_b are both left joins, null rejection occurs on the left child of o_b. I think this is not a case where outer join will be rewritten as inner join, so I recorded this TODO.   -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
