risingwave_frontend/optimizer/rule/
limit_push_down_rule.rs

1// Copyright 2023 RisingWave Labs
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use super::prelude::{PlanRef, *};
16use crate::optimizer::plan_node::{LogicalLimit, LogicalProject, PlanTreeNodeUnary};
17
18pub struct LimitPushDownRule {}
19
20impl Rule<Logical> for LimitPushDownRule {
21    fn apply(&self, plan: PlanRef) -> Option<PlanRef> {
22        let limit: &LogicalLimit = plan.as_logical_limit()?;
23        let project: LogicalProject = limit.input().as_logical_project()?.to_owned();
24        let input = project.input();
25        let logical_limit = limit.clone_with_input(input);
26        Some(project.clone_with_input(logical_limit.into()).into())
27    }
28}
29
30impl LimitPushDownRule {
31    pub fn create() -> BoxedRule {
32        Box::new(LimitPushDownRule {})
33    }
34}