MergeProjectPostProcessor.java

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// to you under the Apache License, Version 2.0 (the
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//   http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.doris.nereids.processor.post;

import org.apache.doris.nereids.CascadesContext;
import org.apache.doris.nereids.trees.expressions.NamedExpression;
import org.apache.doris.nereids.trees.plans.Plan;
import org.apache.doris.nereids.trees.plans.physical.PhysicalProject;

import java.util.List;

/**
 * merge consecutive projects
 */
public class MergeProjectPostProcessor extends PlanPostProcessor {

    @Override
    public PhysicalProject visitPhysicalProject(PhysicalProject<? extends Plan> project, CascadesContext ctx) {
        project = (PhysicalProject<? extends Plan>) super.visit(project, ctx);
        Plan child = project.child();
        if (child instanceof PhysicalProject && project.canMergeProjections((PhysicalProject) child)) {
            List<NamedExpression> projections = project.mergeProjections((PhysicalProject) child);
            return (PhysicalProject) project
                    .withProjectionsAndChild(projections, child.child(0))
                    .copyStatsAndGroupIdFrom(project);
        }
        return project;
    }
}