nuno-faria commented on code in PR #21715:
URL: https://github.com/apache/datafusion/pull/21715#discussion_r3213121882
##########
datafusion/sqllogictest/test_files/cte.slt:
##########
@@ -1319,3 +1319,34 @@ RESET datafusion.execution.enable_recursive_ctes;
statement ok
RESET datafusion.sql_parser.enable_ident_normalization;
+
+# Regression test: functional dependencies from the static (anchor) term of a
+# recursive CTE must NOT be propagated to the outer SubqueryAlias. The
+# recursive term can produce rows that violate any uniqueness constraint that
+# holds for the anchor alone. Without this guard, Filter(pk = const) on the
+# CTE result would be mis-identified as scalar (at most 1 row) and return only
+# one row instead of all matching rows.
+statement ok
+CREATE TABLE pk_table(id INT NOT NULL, val INT NOT NULL, PRIMARY KEY(id));
+
+statement ok
+INSERT INTO pk_table VALUES (1, 100), (2, 200);
+
+# The recursive term produces a second row with id=1 (val=300). Without the
+# FD fix, Filter(nodes.id = 1) would be deemed scalar and return only the
+# first matching row.
+query II rowsort
+WITH RECURSIVE nodes AS (
+ SELECT id, val FROM pk_table
+ UNION ALL
+ SELECT 1 AS id, 300 AS val
+ FROM nodes
+ WHERE nodes.id = 2
+)
+SELECT id, val FROM nodes WHERE id = 1
+----
+1 100
+1 300
Review Comment:
I'm not sure the filter will test the bug here. Shouldn't it be a group by
like `count(*) from nodes group by id, val`?
##########
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:
Since the signature of this pub function has been changed, I think we should
add an entry to the upgrade guide
(docs/source/library-user-guide/upgrading/54.0.0.md).
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