Add lifetime to token #2112
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Add lifetime to token #2112
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Add internal _borrowed() functions that return Cow<\'a, str> to prepare for zero-copy tokenization. When the source string needs no transformation (no escaping), return Cow::Borrowed. When transformation is required, return Cow::Owned. The Token enum still uses String, so borrowed values are converted via to_owned() for now. This maintains API compatibility while preparing the codebase for a future refactor where Token can hold borrowed strings. Optimized: comments, quoted strings, dollar-quoted strings, quoted identifiers.
Key points for this commit: - The peekable trait isn't sufficient for using string slices, as we need the byte indexes (start/end) to create string slices, so added the current byte position to the State struct (Note: in the long term we could potentially remove peekable and use only the current position as an iterator) - Created internal functions that create slices from the original query instead of allocating strings, then converted these functions to return String to maintain compatibility (the idea is to make a small, reviewable commit without changing the Token struct or the parser)
Changed all parsing methods to take '&self' instead of '\&mut self'. Mutable parser state (token index and parser state) now uses for interior mutability. This refactoring is preparation for the borrowed tokenizer work. When holding borrowed tokens from the parser (with lifetime tied to '\&self'), we cannot call methods requiring '\&mut self' due to Rust's borrowing rules. Using interior mutability resolves this conflict by allowing state mutations through shared references.
This change introduces a lifetime parameter 'a to BorrowedToken enum
to prepare for zero-copy tokenization support. This is a foundational
step toward reducing memory allocations during SQL parsing.
Changes:
- Added lifetime parameter to BorrowedToken<'a> enum
- Added _Phantom(Cow<'a, str>) variant to carry the lifetime
- Implemented Visit and VisitMut traits for Cow<'a, str> to support
the visitor pattern with the new lifetime parameter
- Fixed lifetime issues in visitor tests by using tokenized_owned()
instead of tokenize() where owned tokens are required
- Type alias Token = BorrowedToken<'static> maintains backward
compatibility
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his PR adds a lifetime parameter to the Token enum to enable zero-copy tokenization in the future.
Backward Compatibility:
To maintain backward compatibility, we renamed Token to BorrowedToken<'a> and introduced Token as a type alias for BorrowedToken<'static>. This allows existing consumers of the library to continue using Token without needing to handle
lifetimes throughout their code.
New API:
This PR also adds a tokenized_owned() method for use cases where consumers prefer to pay the cost of copying in exchange for owned tokens.
Current State:
This commit does not yet change the tokenizer's behavior—all string allocations remain in place. The goal of the following commits is to replace String with Cow<'a, str> in as many places as possible, leveraging the Borrowed variant to
achieve zero-copy tokenization where feasible.