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

risingwave_frontend/optimizer/rule/stream/
stream_project_merge_rule.rs
