risingwave_frontend/optimizer/rule/
max_one_row_eliminate_rule.rs

1// Copyright 2025 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::{BoxedRule, Rule};
16use crate::optimizer::PlanRef;
17use crate::optimizer::plan_node::{LogicalApply, LogicalMaxOneRow};
18use crate::optimizer::plan_visitor::LogicalCardinalityExt;
19
20/// Eliminate max one row restriction from `LogicalApply`.
21///
22/// If we cannot guarantee that the right side of `Apply` will return at most one row
23/// in compile time, we will add a `MaxOneRow` that does runtime check to satisfy the
24/// max one row restriction.
25///
26/// As a result, the `max_one_row` flag of `LogicalApply` will always be `false`
27/// after applying this rule.
28pub struct MaxOneRowEliminateRule {}
29impl Rule for MaxOneRowEliminateRule {
30    fn apply(&self, plan: PlanRef) -> Option<PlanRef> {
31        let apply: &LogicalApply = plan.as_logical_apply()?;
32        let (left, mut right, on, join_type, correlated_id, correlated_indices, max_one_row) =
33            apply.clone().decompose();
34
35        if !max_one_row {
36            return None;
37        }
38
39        if !right.max_one_row() {
40            right = LogicalMaxOneRow::create(right);
41            debug_assert!(right.max_one_row());
42        }
43
44        Some(LogicalApply::create(
45            left,
46            right,
47            join_type,
48            on,
49            correlated_id,
50            correlated_indices,
51            false,
52        ))
53    }
54}
55
56impl MaxOneRowEliminateRule {
57    pub fn create() -> BoxedRule {
58        Box::new(MaxOneRowEliminateRule {})
59    }
60}
risingwave_frontend/optimizer/rule/max_one_row_eliminate_rule.rs

risingwave_frontend/optimizer/rule/
max_one_row_eliminate_rule.rs
