ProjectProcessor.java

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package org.apache.doris.nereids.trees.plans.logical;

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

import java.util.List;
import java.util.Optional;

/**
 * ProjectProcessor, this class is used to push project/ eliminate project,
 * e.g. LogicalProject(LogicalUnion(child1, child2)) -> LogicalUnion(logicalProject(child1), logicalProject(child2))
 */
public interface ProjectProcessor {
    boolean canProcessProject(List<NamedExpression> parentProjects);

    Optional<Plan> processProject(List<NamedExpression> parentProjects);

    /** tryProcessProject */
    static Optional<Plan> tryProcessProject(List<NamedExpression> parentProjects, Plan plan) {
        if (plan instanceof ProjectProcessor && ((ProjectProcessor) plan).canProcessProject(parentProjects)) {
            return ((ProjectProcessor) plan).processProject(parentProjects);
        } else {
            return Optional.empty();
        }
    }
}