risingwave_frontend/optimizer/plan_expr_rewriter/
const_eval_rewriter.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::error::RwError;
16use crate::expr::{Expr, ExprImpl, ExprRewriter, Literal, default_rewrite_expr};
17
18pub(crate) struct ConstEvalRewriter {
19    pub(crate) error: Option<RwError>,
20}
21impl ExprRewriter for ConstEvalRewriter {
22    fn rewrite_expr(&mut self, expr: ExprImpl) -> ExprImpl {
23        if self.error.is_some() {
24            return expr;
25        }
26        if let Some(result) = expr.try_fold_const() {
27            match result {
28                Ok(datum) => Literal::new(datum, expr.return_type()).into(),
29                Err(e) => {
30                    self.error = Some(e);
31                    expr
32                }
33            }
34        } else if let ExprImpl::Parameter(_) = expr {
35            unreachable!(
36                "Parameter should not appear here. It will be replaced by a literal before this step."
37            )
38        } else {
39            default_rewrite_expr(self, expr)
40        }
41    }
42}