risingwave_frontend/optimizer/plan_visitor/
apply_visitor.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::{DefaultBehavior, LogicalPlanVisitor, Merge};
16use crate::error::{ErrorCode, RwError};
17use crate::optimizer::plan_node::{LogicalApply, LogicalPlanRef as PlanRef, PlanTreeNodeBinary};
18use crate::optimizer::plan_visitor::PlanVisitor;
19
20pub struct HasMaxOneRowApply();
21
22impl LogicalPlanVisitor for HasMaxOneRowApply {
23    type Result = bool;
24
25    type DefaultBehavior = impl DefaultBehavior<Self::Result>;
26
27    fn default_behavior() -> Self::DefaultBehavior {
28        Merge(|a, b| a | b)
29    }
30
31    fn visit_logical_apply(&mut self, plan: &LogicalApply) -> bool {
32        plan.max_one_row() | self.visit(plan.left()) | self.visit(plan.right())
33    }
34}
35
36#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Default)]
37enum CheckResult {
38    #[default]
39    Ok,
40    CannotBeUnnested,
41    MoreThanOneRow,
42}
43
44impl From<CheckResult> for Result<(), RwError> {
45    fn from(val: CheckResult) -> Self {
46        let msg = match val {
47            CheckResult::Ok => return Ok(()),
48            CheckResult::CannotBeUnnested => "Subquery can not be unnested.",
49            CheckResult::MoreThanOneRow => "Scalar subquery might produce more than one row.",
50        };
51
52        Err(ErrorCode::InternalError(msg.to_owned()).into())
53    }
54}
55
56#[derive(Default)]
57pub struct CheckApplyElimination {
58    result: CheckResult,
59}
60
61impl LogicalPlanVisitor for CheckApplyElimination {
62    type Result = ();
63
64    type DefaultBehavior = impl DefaultBehavior<Self::Result>;
65
66    fn default_behavior() -> Self::DefaultBehavior {
67        Merge(std::cmp::max)
68    }
69
70    fn visit_logical_apply(&mut self, plan: &LogicalApply) {
71        // If there's a runtime max-one-row check on the right side, it's likely to be the
72        // reason for the failed unnesting. Report users with a more precise error message.
73        if plan.right().as_logical_max_one_row().is_some() {
74            self.result = CheckResult::MoreThanOneRow;
75        } else {
76            self.result = CheckResult::CannotBeUnnested;
77        }
78    }
79}
80
81#[easy_ext::ext(PlanCheckApplyEliminationExt)]
82impl PlanRef {
83    /// Checks if all `LogicalApply` nodes in the plan have been eliminated, that is,
84    /// subqueries are successfully unnested.
85    pub fn check_apply_elimination(&self) -> Result<(), RwError> {
86        let mut visitor = CheckApplyElimination::default();
87        visitor.visit(self.clone());
88        visitor.result.into()
89    }
90}
risingwave_frontend/optimizer/plan_visitor/apply_visitor.rs

risingwave_frontend/optimizer/plan_visitor/
apply_visitor.rs
