EliminateJoinByUnique.java

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//   http://www.apache.org/licenses/LICENSE-2.0
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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.plans.logical.LogicalJoin;
import org.apache.doris.nereids.util.JoinUtils;

/**
 * Eliminate outer join.
 */
public class EliminateJoinByUnique extends OneRewriteRuleFactory {
    // TODO: support distinct -> LOJ
    @Override
    public Rule build() {
        return logicalProject(
                logicalJoin().when(join -> join.getJoinType().isLeftOuterJoin())
        ).then(project -> {
            LogicalJoin<?, ?> join = project.child();
            if (!join.left().getOutputSet().containsAll(project.getInputSlots())) {
                return project;
            }
            if (!JoinUtils.canEliminateByLeft(join,
                    join.right().getLogicalProperties().getTrait())) {
                return project;
            }
            return project.withChildren(join.left());
        }).toRule(RuleType.ELIMINATE_JOIN_BY_UK);
    }
}