Implement zero-copy tokenization for identifiers, strings, and comments #2136
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Implement zero-copy tokenization for identifiers, strings, and comments #2136eyalleshem wants to merge 2 commits intoapache:reduce-string-copyingfrom
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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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…hitespace Convert token string fields to use Cow<'a, str> to enable zero-copy tokenization for commonly used tokens: - Word.value: Regular identifiers and keywords now borrow from source - SingleQuotedString: String literals borrow when no escape processing needed - Whitespace: Single-line and multi-line comments borrow from source Also add benchmark for measuring tokenization performance
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This PR implements zero-copy tokenization by using borrowed strings (
&str) instead of owned strings (String) for identifiers, string literals, and comments. This eliminates unnecessary string allocations during the tokenizationprocess.
Changes
Tokenvariants to store&'a strinstead ofStringfor:Wordtokens (identifiers like table/column names)SingleQuotedStringliteralsWhitespaceto_uppercase()allocationtokenize_benchcriterion benchmark for performance measurementPerformance Impact
Benchmark results using a complex 27KB SQL query with CTEs, joins, window functions, and extensive comments:
tokenization/tokenize_complex_sql
time: [254.68 µs 254.81 µs 254.97 µs]
change: [−60.885% −60.682% −60.482%] (p = 0.00 < 0.05)
Performance has improved.