fix order by process not copy ambiguous names

Author: xiedeyantu

datafusion/common/src/dfschema.rs

@@ -380,6 +380,11 @@ impl DFSchema {
         let finished_with_metadata = finished.with_metadata(metadata);
         self.inner = finished_with_metadata.into();
         self.field_qualifiers.extend(qualifiers);
+        // Propagate ambiguous names from the other schema so that names marked
+        // as ambiguous (e.g. by a JOIN) are not silently dropped when schemas
+        // are merged for ORDER BY / HAVING resolution.
+        self.ambiguous_names
+            .extend(other_schema.ambiguous_names.iter().cloned());
     }
 
     /// Get a list of fields for this schema

datafusion/sql/tests/sql_integration.rs

@@ -3938,6 +3938,19 @@ fn order_by_ambiguous_name() {
     );
 }
 
+#[test]
+fn order_by_ambiguous_name_via_subquery() {
+    // `age` is not in the SELECT list; ORDER BY falls back to the FROM schema,
+    // which is a subquery over a JOIN — `age` must still be flagged ambiguous.
+    let sql = "SELECT id FROM (SELECT * FROM person a JOIN person b USING (id)) sub ORDER BY age";
+    let err = logical_plan(sql).unwrap_err().strip_backtrace();
+
+    assert_snapshot!(
+        err,
+        @"Schema error: Ambiguous reference to unqualified field age"
+    );
+}
+
 #[test]
 fn group_by_ambiguous_name() {
     let sql = "select max(id) from person a join person b using (id) group by age";