risingwave_frontend/optimizer/rule/
cross_join_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 risingwave_pb::plan_common::JoinType;
16
17use super::{BoxedRule, Rule};
18use crate::optimizer::PlanRef;
19use crate::optimizer::plan_node::{LogicalJoin, LogicalValues};
20
21/// Eliminate trivial cross join generated by subquery unnesting.
22///
23/// Before:
24///
25/// ```text
26///             LogicalJoin (join type: inner, on condition: true)
27///             /      \
28///          Input    Value (with one row but no columns)
29/// ```
30///
31/// After:
32///
33///
34/// ```text
35///              Input
36/// ```
37pub struct CrossJoinEliminateRule {}
38impl Rule for CrossJoinEliminateRule {
39    fn apply(&self, plan: PlanRef) -> Option<PlanRef> {
40        let join: &LogicalJoin = plan.as_logical_join()?;
41        let (left, right, on, join_type, _output_indices) = join.clone().decompose();
42        let values: &LogicalValues = right.as_logical_values()?;
43        if on.always_true() // cross join
44            && join_type == JoinType::Inner
45            && values.rows().len() == 1 // one row
46            && values.rows()[0].is_empty() // no columns
47            && join.output_indices_are_trivial()
48        {
49            Some(left)
50        } else {
51            None
52        }
53    }
54}
55
56impl CrossJoinEliminateRule {
57    pub fn create() -> BoxedRule {
58        Box::new(CrossJoinEliminateRule {})
59    }
60}
risingwave_frontend/optimizer/rule/cross_join_eliminate_rule.rs

risingwave_frontend/optimizer/rule/
cross_join_eliminate_rule.rs
