EliminateDedupJoinCondition.java

// 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.doris.nereids.rules.rewrite;

import org.apache.doris.nereids.rules.Rule;
import org.apache.doris.nereids.rules.RuleType;
import org.apache.doris.nereids.trees.expressions.Expression;

import java.util.List;
import java.util.stream.Collectors;

/**
 * Eliminate duplicate join condition.
 * For example:
 * Join condition: a = b and a = b -> a = b
 */
public class EliminateDedupJoinCondition extends OneRewriteRuleFactory {
    @Override
    public Rule build() {
        return logicalJoin().then(join -> {
            List<Expression> dedupHashJoinConjuncts = join.getHashJoinConjuncts().stream()
                    .distinct().collect(Collectors.toList());
            List<Expression> dedupOtherJoinConjuncts = join.getOtherJoinConjuncts().stream()
                    .distinct().collect(Collectors.toList());
            List<Expression> dedupMarkJoinConjuncts = join.getMarkJoinConjuncts().stream()
                    .distinct().collect(Collectors.toList());
            if (dedupHashJoinConjuncts.size() == join.getHashJoinConjuncts().size()
                    && dedupOtherJoinConjuncts.size() == join.getOtherJoinConjuncts().size()
                    && dedupMarkJoinConjuncts.size() == join.getMarkJoinConjuncts().size()) {
                return null;
            }
            return join.withJoinConjuncts(dedupHashJoinConjuncts, dedupOtherJoinConjuncts, dedupMarkJoinConjuncts,
                        join.getJoinReorderContext());
        }).toRule(RuleType.ELIMINATE_DEDUP_JOIN_CONDITION);
    }
}