risingwave_frontend/optimizer/rule/stream/
stream_project_merge_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 crate::expr::{ExprImpl, ExprRewriter, ExprVisitor};
16use crate::optimizer::plan_expr_visitor::InputRefCounter;
17use crate::optimizer::plan_node::{PlanTreeNodeUnary, StreamProject, generic};
18use crate::optimizer::rule::Rule;
19use crate::optimizer::{BoxedRule, PlanRef};
20use crate::utils::Substitute;
21
22/// Merge contiguous [`StreamProject`] nodes.
23pub struct StreamProjectMergeRule {}
24impl Rule for StreamProjectMergeRule {
25    fn apply(&self, plan: PlanRef) -> Option<PlanRef> {
26        let outer_project = plan.as_stream_project()?;
27        let input = outer_project.input();
28        let inner_project = input.as_stream_project()?;
29
30        let mut input_ref_counter = InputRefCounter::default();
31        for expr in outer_project.exprs() {
32            input_ref_counter.visit_expr(expr);
33        }
34        // bail out if it is a project generated by `CommonSubExprExtractRule`.
35        for (index, count) in &input_ref_counter.counter {
36            if *count > 1 && matches!(inner_project.exprs()[*index], ExprImpl::FunctionCall(_)) {
37                return None;
38            }
39        }
40
41        let mut subst = Substitute {
42            mapping: inner_project.exprs().clone(),
43        };
44        let exprs = outer_project
45            .exprs()
46            .iter()
47            .cloned()
48            .map(|expr| subst.rewrite_expr(expr))
49            .collect();
50        let logical_project = generic::Project::new(exprs, inner_project.input());
51
52        // If either of the projects has the hint, we should keep it.
53        let noop_update_hint = outer_project.noop_update_hint() || inner_project.noop_update_hint();
54
55        Some(
56            StreamProject::new(logical_project)
57                .with_noop_update_hint(noop_update_hint)
58                .into(),
59        )
60    }
61}
62
63impl StreamProjectMergeRule {
64    pub fn create() -> BoxedRule {
65        Box::new(StreamProjectMergeRule {})
66    }
67}
risingwave_frontend/optimizer/rule/stream/stream_project_merge_rule.rs

risingwave_frontend/optimizer/rule/stream/
stream_project_merge_rule.rs
