EliminateLimit.java

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

import org.apache.doris.nereids.rules.Rule;
import org.apache.doris.nereids.rules.RuleType;
import org.apache.doris.nereids.trees.expressions.StatementScopeIdGenerator;
import org.apache.doris.nereids.trees.plans.logical.LogicalEmptyRelation;

import com.google.common.collect.ImmutableList;

import java.util.List;

/**
 * Eliminate limit = 0.
 */
public class EliminateLimit implements RewriteRuleFactory {

    @Override
    public List<Rule> buildRules() {
        return ImmutableList.of(
                logicalLimit()
                        .when(limit -> limit.getLimit() == 0)
                        .thenApply(ctx -> new LogicalEmptyRelation(ctx.statementContext.getNextRelationId(),
                                ctx.root.getOutput()))
                        .toRule(RuleType.ELIMINATE_LIMIT),
                logicalLimit(logicalOneRowRelation())
                        .then(limit -> limit.getLimit() > 0 && limit.getOffset() == 0
                                ? limit.child() : new LogicalEmptyRelation(StatementScopeIdGenerator.newRelationId(),
                                limit.child().getOutput()))
                        .toRule(RuleType.ELIMINATE_LIMIT_ON_ONE_ROW_RELATION)
        );
    }
}