ScalarApplyToJoin.java

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

import org.apache.doris.nereids.exceptions.AnalysisException;
import org.apache.doris.nereids.hint.DistributeHint;
import org.apache.doris.nereids.rules.Rule;
import org.apache.doris.nereids.rules.RuleType;
import org.apache.doris.nereids.trees.expressions.AssertNumRowsElement;
import org.apache.doris.nereids.trees.expressions.EqualTo;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.plans.DistributeType;
import org.apache.doris.nereids.trees.plans.JoinType;
import org.apache.doris.nereids.trees.plans.Plan;
import org.apache.doris.nereids.trees.plans.logical.LogicalApply;
import org.apache.doris.nereids.trees.plans.logical.LogicalAssertNumRows;
import org.apache.doris.nereids.trees.plans.logical.LogicalJoin;
import org.apache.doris.nereids.trees.plans.logical.LogicalPlan;
import org.apache.doris.nereids.util.ExpressionUtils;

import java.util.Optional;

/**
 * Convert scalarApply to LogicalJoin.
 * <p>
 * UnCorrelated -> CROSS_JOIN
 * Correlated -> LEFT_OUTER_JOIN
 */
public class ScalarApplyToJoin extends OneRewriteRuleFactory {
    @Override
    public Rule build() {
        return logicalApply().when(LogicalApply::isScalar).then(apply -> {
            // apply.isCorrelated() only check if correlated slot exits
            // but correlation filter may be eliminated by SimplifyConflictCompound rule
            // so we need check both correlated slot and correlation filter exists before creating LogicalJoin node
            if (apply.isCorrelated() && apply.getCorrelationFilter().isPresent()) {
                return correlatedToJoin(apply);
            } else {
                return unCorrelatedToJoin(apply);
            }
        }).toRule(RuleType.SCALAR_APPLY_TO_JOIN);
    }

    private Plan unCorrelatedToJoin(LogicalApply apply) {
        LogicalAssertNumRows assertNumRows = new LogicalAssertNumRows<>(new AssertNumRowsElement(1,
                apply.right().toString(), AssertNumRowsElement.Assertion.EQ),
                (LogicalPlan) apply.right());
        return new LogicalJoin<>(JoinType.CROSS_JOIN,
                ExpressionUtils.EMPTY_CONDITION,
                ExpressionUtils.EMPTY_CONDITION,
                new DistributeHint(DistributeType.NONE),
                apply.getMarkJoinSlotReference(),
                (LogicalPlan) apply.left(), assertNumRows, null);
    }

    private Plan correlatedToJoin(LogicalApply apply) {
        Optional<Expression> correlationFilter = apply.getCorrelationFilter();

        if (correlationFilter.isPresent()) {
            ExpressionUtils.extractConjunction(correlationFilter.get()).stream()
                    .filter(e -> !(e instanceof EqualTo))
                    .forEach(e -> {
                        throw new AnalysisException(
                                "scalar subquery's correlatedPredicates's operator must be EQ");
                    });
        } else {
            throw new AnalysisException("correlationFilter can't be null in correlatedToJoin");
        }

        return new LogicalJoin<>(
                apply.isNeedAddSubOutputToProjects() ? JoinType.LEFT_OUTER_JOIN : JoinType.LEFT_SEMI_JOIN,
                ExpressionUtils.EMPTY_CONDITION,
                ExpressionUtils.extractConjunction(correlationFilter.get()),
                new DistributeHint(DistributeType.NONE),
                apply.getMarkJoinSlotReference(),
                apply.children(), null);
    }
}