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sql: avoid stack overflow on deeply nested ASTs
In the SQL planner, use the same technique as the SQL parser for automatically growing the stack when presented with a deeply nested AST. The stack-checking code is generalized and moved to a new `ore::stack` module. Fix #9103.
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| Original file line number | Diff line number | Diff line change |
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| // Copyright Materialize, Inc. and contributors. All rights reserved. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License in the LICENSE file at the | ||
| // root of this repository, or online at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
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| //! Stack management utilities. | ||
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| use std::cell::RefCell; | ||
| use std::error::Error; | ||
| use std::fmt; | ||
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| // The red zone is the amount of stack space that must be available on | ||
| // the current stack in order to call `f` without allocating a new | ||
| // stack. | ||
| const STACK_RED_ZONE: usize = 32 << 10; // 32KiB | ||
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| // The size of any freshly-allocated stacks. It was chosen to match the | ||
| // default stack size for threads in Rust. | ||
| const STACK_SIZE: usize = 2 << 20; // 2MiB | ||
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| /// A trait for types which support recursion without stack overflow. | ||
| pub trait CheckedRecursion { | ||
| /// Extracts a reference to the recursion guard embedded within the type. | ||
| fn recursion_guard(&self) -> &RecursionGuard; | ||
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| /// Checks whether it is safe to recur and calls `f` if so. | ||
| /// | ||
| /// If the recursion limit `LIMIT` has been reached, returns a | ||
| /// `RecursionLimitError`. Otherwise, it will call `f`, possibly growing | ||
| /// the stack if necessary. | ||
| /// | ||
| /// Calls to this function must be manually inserted at any point that | ||
| /// mutual recursion occurs. | ||
| fn checked_recur<F, T, E>(&self, f: F) -> Result<T, E> | ||
| where | ||
| F: FnOnce(&Self) -> Result<T, E>, | ||
| E: From<RecursionLimitError>, | ||
| { | ||
| self.recursion_guard().descend()?; | ||
| let out = stacker::maybe_grow(STACK_RED_ZONE, STACK_SIZE, || f(self)); | ||
| self.recursion_guard().ascend(); | ||
| out | ||
| } | ||
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| /// Like [`CheckedRecursion::checked_recur`], but operates on a mutable | ||
| /// reference to `Self`. | ||
| fn checked_recur_mut<F, T, E>(&mut self, f: F) -> Result<T, E> | ||
| where | ||
| F: FnOnce(&mut Self) -> Result<T, E>, | ||
| E: From<RecursionLimitError>, | ||
| { | ||
| self.recursion_guard().descend()?; | ||
| let out = stacker::maybe_grow(STACK_RED_ZONE, STACK_SIZE, || f(self)); | ||
| self.recursion_guard().ascend(); | ||
| out | ||
| } | ||
| } | ||
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| /// A guard which is embedded in a type that implements [`CheckedRecursion`] | ||
| /// to track the depth of recursion. | ||
| #[derive(Default, Debug, Clone)] | ||
| pub struct RecursionGuard { | ||
| depth: RefCell<usize>, | ||
| limit: usize, | ||
| } | ||
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| impl RecursionGuard { | ||
| /// Constructs a new recursion guard with the specified recursion | ||
| /// limit. | ||
| pub fn with_limit(limit: usize) -> RecursionGuard { | ||
| RecursionGuard { | ||
| depth: RefCell::new(0), | ||
| limit, | ||
| } | ||
| } | ||
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| fn descend(&self) -> Result<(), RecursionLimitError> { | ||
| let mut depth = self.depth.borrow_mut(); | ||
| if *depth < self.limit { | ||
| *depth += 1; | ||
| Ok(()) | ||
| } else { | ||
| Err(RecursionLimitError) | ||
| } | ||
| } | ||
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| fn ascend(&self) { | ||
| *self.depth.borrow_mut() -= 1; | ||
| } | ||
| } | ||
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| /// A [`RecursionGuard`]'s recursion limit was reached. | ||
| #[derive(Clone, Debug)] | ||
| pub struct RecursionLimitError; | ||
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| impl fmt::Display for RecursionLimitError { | ||
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | ||
| f.write_str("recursion limit exceeded") | ||
| } | ||
| } | ||
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| impl Error for RecursionLimitError {} |
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