DefaultPlanRewriter.java

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

import org.apache.doris.nereids.trees.plans.Plan;
import org.apache.doris.nereids.trees.plans.physical.AbstractPhysicalPlan;
import org.apache.doris.nereids.trees.plans.physical.PhysicalOlapScan;
import org.apache.doris.nereids.trees.plans.physical.PhysicalStorageLayerAggregate;

import com.google.common.collect.ImmutableList;

/**
 * Default implementation for plan rewriting, delegating to child plans and rewrite current root
 * when any one of its children changed.
 */
public abstract class DefaultPlanRewriter<C> extends PlanVisitor<Plan, C> {

    @Override
    public Plan visit(Plan plan, C context) {
        return visitChildren(this, plan, context);
    }

    @Override
    public Plan visitPhysicalStorageLayerAggregate(PhysicalStorageLayerAggregate storageLayerAggregate, C context) {
        if (storageLayerAggregate.getRelation() instanceof PhysicalOlapScan) {
            PhysicalOlapScan olapScan = (PhysicalOlapScan) storageLayerAggregate.getRelation().accept(this, context);
            if (olapScan != storageLayerAggregate.getRelation()) {
                return storageLayerAggregate.withPhysicalOlapScan(olapScan);
            }
        }
        return storageLayerAggregate;
    }

    /** visitChildren */
    public static <P extends Plan, C> P visitChildren(DefaultPlanRewriter<C> rewriter, P plan, C context) {
        ImmutableList.Builder<Plan> newChildren = ImmutableList.builderWithExpectedSize(plan.arity());
        boolean hasNewChildren = false;
        for (Plan child : plan.children()) {
            Plan newChild = child.accept(rewriter, context);
            if (newChild != child) {
                hasNewChildren = true;
            }
            newChildren.add(newChild);
        }

        if (hasNewChildren) {
            P originPlan = plan;
            plan = (P) plan.withChildren(newChildren.build());
            if (originPlan instanceof AbstractPhysicalPlan) {
                plan = (P) ((AbstractPhysicalPlan) plan).copyStatsAndGroupIdFrom((AbstractPhysicalPlan) originPlan);
            }
        }
        return plan;
    }
}