docs: clarify difference between try_cast_literal_to_type and ScalarValue::cast_to#22592
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…alue::cast_to These two casts are easy to confuse. Document on each how it differs: - `ScalarValue::cast_to` / `cast_to_with_options`: general-purpose, Arrow cast-kernel based, returns `Result`, and may be lossy or cross-kind (parsing strings to numbers, formatting, truncating decimals, Date -> Timestamp, ...). Points readers to try_cast_literal_to_type for the value-preserving variant. - `try_cast_literal_to_type`: value-preserving cast used to unwrap `CAST(col AS T) = literal` comparisons; returns `None` rather than performing a lossy/cross-kind conversion. Documents exactly which casts it attempts and the timestamp-unit truncation exception. Towards apache#22577. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
alamb
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May 28, 2026
| use datafusion_common::ScalarValue; | ||
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| /// Convert a literal value from one data type to another | ||
| /// Convert a literal [`ScalarValue`] to `target_type`, preserving the exact value. |
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the exact value part was very unclear to me at first
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Which issue does this PR close?
ScalarValuecast implementations).Rationale for this change
I have been confused about the difference between
ScalarValue::cast_toandtry_cast_literal_to_type-- so after some research I would like to make the difference clearerWhat changes are included in this PR?
Document on each function how it differs from the other, so the choice is obvious from the docs alone.
Are these changes tested?
by CI
Are there any user-facing changes?
Doc comments only. No code or API changes.
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