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package org.apache.doris.nereids.rules.rewrite;

import org.apache.doris.nereids.jobs.JobContext;
import org.apache.doris.nereids.trees.expressions.NamedExpression;
import org.apache.doris.nereids.trees.plans.Plan;
import org.apache.doris.nereids.trees.plans.logical.LogicalAggregate;
import org.apache.doris.nereids.trees.plans.logical.LogicalJoin;
import org.apache.doris.nereids.trees.plans.logical.LogicalProject;
import org.apache.doris.nereids.trees.plans.visitor.CustomRewriter;
import org.apache.doris.nereids.trees.plans.visitor.DefaultPlanRewriter;

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

/**
 * The rule add an explicit project at the top join to ensure the output of whole plan is stable
 * and avoid generate circle in memo.
 *
 */
public class EnsureProjectOnTopJoin extends DefaultPlanRewriter<Void> implements CustomRewriter {

    @Override
    public Plan rewriteRoot(Plan plan, JobContext jobContext) {
        return plan.accept(this, null);
    }

    @Override
    public Plan visitLogicalAggregate(LogicalAggregate<? extends Plan> aggregate, Void context) {
        return aggregate;
    }

    @Override
    public Plan visitLogicalProject(LogicalProject<? extends Plan> project, Void context) {
        return project;
    }

    @Override
    public Plan visitLogicalJoin(LogicalJoin<? extends Plan, ? extends Plan> join, Void context) {
        List<NamedExpression> projects = join.getOutput().stream()
                .map(NamedExpression.class::cast)
                .collect(Collectors.toList());
        return new LogicalProject<>(projects, join);
    }
}
