risingwave_frontend/optimizer/rule/
empty_agg_remove_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::super::plan_node::*;
16use super::{BoxedRule, Rule};
17use crate::optimizer::plan_node::generic::GenericPlanRef;
18
19/// Remove empty output [`LogicalAgg`] nodes.
20pub struct EmptyAggRemoveRule {}
21impl Rule for EmptyAggRemoveRule {
22    fn apply(&self, plan: PlanRef) -> Option<PlanRef> {
23        let agg = plan.as_logical_agg()?;
24        if agg.agg_calls().is_empty() && agg.group_key().is_empty() {
25            assert!(agg.schema().is_empty());
26            // empty simple agg should produce a single empty row
27            Some(LogicalValues::new(vec![vec![]], agg.schema().clone(), agg.ctx()).into())
28        } else {
29            None
30        }
31    }
32}
33
34impl EmptyAggRemoveRule {
35    pub fn create() -> BoxedRule {
36        Box::new(EmptyAggRemoveRule {})
37    }
38}

risingwave_frontend/optimizer/rule/empty_agg_remove_rule.rs

risingwave_frontend/optimizer/rule/
empty_agg_remove_rule.rs