xiedeyantu commented on code in PR #21715:
URL: https://github.com/apache/datafusion/pull/21715#discussion_r3213225974
##########
datafusion/common/src/functional_dependencies.rs:
##########
@@ -196,15 +196,25 @@ impl FunctionalDependencies {
}
/// Creates a new `FunctionalDependencies` object from the given
constraints.
+ ///
+ /// `nullable_flags` must contain one entry per field in the relation,
+ /// indicating whether that field is nullable. A `UNIQUE` constraint whose
+ /// source columns include any nullable field is **not** a functional
+ /// dependency — because SQL treats `NULL` values as distinct, multiple
rows
+ /// may carry `NULL` in a unique-key column without violating the
constraint.
+ /// Such constraints are therefore omitted entirely. When all source
columns
+ /// are non-nullable a `UNIQUE` constraint is equivalent to a primary key
and
+ /// is recorded with `nullable = false`.
pub fn new_from_constraints(
constraints: Option<&Constraints>,
- n_field: usize,
+ nullable_flags: &[bool],
) -> Self {
Review Comment:
Added!
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