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, Merge};
16use crate::PlanRef;
17use crate::error::{ErrorCode, RwError};
18use crate::optimizer::plan_node::{LogicalApply, PlanTreeNodeBinary};
19use crate::optimizer::plan_visitor::PlanVisitor;
20
21pub struct HasMaxOneRowApply();
22
23impl PlanVisitor for HasMaxOneRowApply {
24    type Result = bool;
25
26    type DefaultBehavior = impl DefaultBehavior<Self::Result>;
27
28    fn default_behavior() -> Self::DefaultBehavior {
29        Merge(|a, b| a | b)
30    }
31
32    fn visit_logical_apply(&mut self, plan: &LogicalApply) -> bool {
33        plan.max_one_row() | self.visit(plan.left()) | self.visit(plan.right())
34    }
35}
36
37#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Default)]
38enum CheckResult {
39    #[default]
40    Ok,
41    CannotBeUnnested,
42    MoreThanOneRow,
43}
44
45impl From<CheckResult> for Result<(), RwError> {
46    fn from(val: CheckResult) -> Self {
47        let msg = match val {
48            CheckResult::Ok => return Ok(()),
49            CheckResult::CannotBeUnnested => "Subquery can not be unnested.",
50            CheckResult::MoreThanOneRow => "Scalar subquery might produce more than one row.",
51        };
52
53        Err(ErrorCode::InternalError(msg.to_owned()).into())
54    }
55}
56
57#[derive(Default)]
58pub struct CheckApplyElimination {
59    result: CheckResult,
60}
61
62impl PlanVisitor for CheckApplyElimination {
63    type Result = ();
64
65    type DefaultBehavior = impl DefaultBehavior<Self::Result>;
66
67    fn default_behavior() -> Self::DefaultBehavior {
68        Merge(std::cmp::max)
69    }
70
71    fn visit_logical_apply(&mut self, plan: &LogicalApply) {
72        // If there's a runtime max-one-row check on the right side, it's likely to be the
73        // reason for the failed unnesting. Report users with a more precise error message.
74        if plan.right().as_logical_max_one_row().is_some() {
75            self.result = CheckResult::MoreThanOneRow;
76        } else {
77            self.result = CheckResult::CannotBeUnnested;
78        }
79    }
80}
81
82#[easy_ext::ext(PlanCheckApplyEliminationExt)]
83impl PlanRef {
84    /// Checks if all `LogicalApply` nodes in the plan have been eliminated, that is,
85    /// subqueries are successfully unnested.
86    pub fn check_apply_elimination(&self) -> Result<(), RwError> {
87        let mut visitor = CheckApplyElimination::default();
88        visitor.visit(self.clone());
89        visitor.result.into()
90    }
91}
risingwave_frontend/optimizer/plan_visitor/apply_visitor.rs

risingwave_frontend/optimizer/plan_visitor/
apply_visitor.rs
