PullUpProjectUnderTopN.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.rules.rewrite;

import org.apache.doris.nereids.properties.OrderKey;
import org.apache.doris.nereids.rules.Rule;
import org.apache.doris.nereids.rules.RuleType;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.Slot;
import org.apache.doris.nereids.trees.plans.Plan;
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.logical.LogicalTopN;
import org.apache.doris.nereids.util.ExpressionUtils;
import org.apache.doris.nereids.util.PlanUtils;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;

/**
 * Pull up Project under TopN for PushDownTopNThroughJoin
 */
public class PullUpProjectUnderTopN extends OneRewriteRuleFactory {
    @Override
    public Rule build() {
        return logicalTopN(
                logicalProject(logicalJoin().when(j -> j.getJoinType().isLeftRightOuterOrCrossJoin()))
                        .whenNot(p -> p.isAllSlots()))
                .then(topN -> {
                    LogicalProject<LogicalJoin<Plan, Plan>> project = topN.child();
                    Set<Slot> outputSet = project.child().getOutputSet();

                    Map<Slot, Expression> slotMap = ExpressionUtils.generateReplaceMap(project.getProjects());
                    List<OrderKey> newOrderKeys = new ArrayList<>();
                    for (OrderKey orderKey : topN.getOrderKeys()) {
                        if (!(orderKey.getExpr() instanceof Slot)) {
                            return null;
                        }
                        Expression expression = slotMap.get((Slot) orderKey.getExpr());
                        if (expression instanceof Slot) {
                            newOrderKeys.add(orderKey.withExpression(expression));
                        } else {
                            return null;
                        }
                    }

                    Set<Slot> allUsedSlots = project.getProjects().stream().flatMap(ne -> ne.getInputSlots().stream())
                            .collect(Collectors.toSet());
                    LogicalTopN<Plan> newTopN = topN.withOrderKeys(newOrderKeys);
                    if (outputSet.size() == allUsedSlots.size()) {
                        Preconditions.checkState(outputSet.equals(allUsedSlots));
                        return project.withChildren(newTopN.withChildren(project.child()));
                    } else {
                        Plan columnProject = PlanUtils.projectOrSelf(ImmutableList.copyOf(allUsedSlots),
                                project.child());
                        return project.withChildren(newTopN.withChildren(columnProject));
                    }
                }).toRule(RuleType.PULL_UP_PROJECT_UNDER_TOPN);
    }
}