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Add CAST expression support to parser#3207

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apache:mainfrom
nssalian:cast-expression-support
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Add CAST expression support to parser#3207
nssalian wants to merge 3 commits into
apache:mainfrom
nssalian:cast-expression-support

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Closes #198

Picks up where #209 left off with @Fokko's feedback addressed. Thanks @jayceslesar for the original work.

Rationale for this change

Adds CAST(column AS type) parsing that maps to Iceberg transforms (dateDayTransform, yearYearTransform, monthMonthTransform, hourHourTransform). Also implements BoundTransform.ref() and eval() — both were missing abstract methods required by BoundTerm. Introduces UnboundTransform with bind() that validates via can_transform().

Are these changes tested?

Yes. 11 new tests covering all transform types, case insensitivity, nested fields, unsupported types, comparison operators, and boolean composition.

Are there any user-facing changes?

No.

@nssalian nssalian marked this pull request as ready for review March 30, 2026 15:46
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@Fokko @geruh @kevinjqliu PTAL

Comment thread pyiceberg/expressions/parser.py
Comment on lines +285 to +288
expected = EqualTo(
UnboundTransform(Reference("created_at"), DayTransform()),
StringLiteral("2024-01-01"),
)
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For testing, I think it would be good to have an integration test as well. The StringLiteral should be converted to a DateLiteral when bound to the transform.

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Added a unit test for this.

@nssalian nssalian requested a review from Fokko June 2, 2026 04:41
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Add CAST to parser.py

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