SplitLimit.java

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

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.plans.LimitPhase;
import org.apache.doris.nereids.trees.plans.logical.LogicalLimit;

/**
 * Split limit into two phase
 * before:
 *  Limit(origin) limit, offset
 * after:
 *  Limit(global) limit, offset
 *      |
 *  Limit(local) limit + offset, 0
 */
public class SplitLimit extends OneRewriteRuleFactory {
    @Override
    public Rule build() {
        return logicalLimit().when(limit -> !limit.isSplit())
                .then(limit -> {
                    long l = limit.getLimit();
                    long o = limit.getOffset();
                    return new LogicalLimit<>(l, o,
                            LimitPhase.GLOBAL, new LogicalLimit<>(l + o, 0, LimitPhase.LOCAL, limit.child())
                    );
                }).toRule(RuleType.SPLIT_LIMIT);
    }
}