LuciferYang opened a new pull request, #57486:
URL: https://github.com/apache/spark/pull/57486
### What changes were proposed in this pull request?
`ToTime` (the `to_time` function) is a `RuntimeReplaceable`, so its
`dataType` comes from `replacement.dataType`. When the format argument is
foldable and evaluates to NULL, the replacement fell back to `Literal(null,
expr.dataType)`, where `expr` is the format argument, so the whole expression
reported the format's type (STRING) instead of TIME. This changes the fallback
to `Literal(null, TimeType())`, so `to_time` reports `TimeType()` like all of
its other branches.
### Why are the changes needed?
`to_time(str, fmt)` with a foldable NULL `fmt` reports the wrong type.
`SELECT typeof(to_time('00:12:00', null))` returns `string` instead of
`time(6)`, and the analyzed plan carries STRING for that column, so schema
inference and UNION type coercion (against a real TIME column) use the wrong
type. The value is NULL either way, but the type is user-visible and wrong. The
inconsistency is also internal: a non-foldable NULL format takes the
`invokeParser()` branch and correctly yields `time(6)`, so the result type
depended on whether the format happened to be foldable.
### Does this PR introduce _any_ user-facing change?
Yes. `to_time(str, fmt)` with a foldable NULL `fmt` now has type `time(6)`
instead of STRING, consistent with all other forms of `to_time`. The returned
value (NULL) is unchanged. This is a bug fix: the wrong type has been present
since `to_time` was introduced in 4.1.0.
### How was this patch tested?
Added a `TimeExpressionsSuite` case asserting `ToTime(...).dataType ===
TimeType()` for both an untyped and a STRING-typed foldable NULL format; it
fails on the unfixed tree with `StringType did not equal TimeType(6)`. The same
case also asserts the value is still NULL via `checkEvaluation`. Also added two
golden queries in `time.sql` whose schema now locks in `time(6)`.
### Was this patch authored or co-authored using generative AI tooling?
Generated-by: Claude Code (Opus 4.8)
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