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VLCDaniel
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Apr 7, 2026
| // silently widen the column (e.g. Int32 → Utf8), and | ||
| // (b) incompatible assignments (e.g. a non-numeric string into an Int32 | ||
| // column) are caught during plan optimisation via constant folding. | ||
| let typed_expr = cast(expr.to_owned(), field.data_type().clone()); |
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DataFusion silently coerces incompatible types in CASE expressions (e.g. promoting Int32 to Utf8 when a string expression is assigned to an integer column) instead of erroring. Without an explicit check, a type-mismatched update would succeed and write a parquet file with the wrong column type
test_expected_failures exposed this, this is how it fails now:
Optimizer rule 'simplify_expressions' failed
caused by
Arrow error: Cast error: Cannot cast string 'a string' to value of Int32 type
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ACTION NEEDED delta-rs follows the Conventional Commits specification for release automation. The PR title and description are used as the merge commit message. Please update your PR title and description to match the specification. |
cdobre
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Apr 9, 2026
…nt silent type coercion
VLCDaniel
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Without this, updates/merges would silently corrupt your table:
table.update().with_update("age", lit("hello")).await // age is Int32DataFusion would quietly change the age column type from
Int32toUtf8in the written parquet file, while the Delta log still said it wasInt32.