Fix min/max rows logic for Deduplication.

python/lsst/daf/relation/_operations/_deduplication.py

@@ -53,7 +53,13 @@ def __str__(self) -> str:
 
     def applied_min_rows(self, target: Relation) -> int:
         # Docstring inherited.
-        return 1
+        return 1 if target.min_rows >= 1 else 0
+
+    def applied_max_rows(self, target: Relation) -> int | None:
+        # Docstring inherited.
+        if not target.columns:
+            return 1 if target.max_rows is None or target.max_rows >= 1 else 0
+        return target.max_rows
 
     def commute(self, current: UnaryOperationRelation) -> UnaryCommutator:
         # Docstring inherited.

tests/test_deduplication.py

@@ -63,6 +63,16 @@ def test_attributes(self) -> None:
         self.assertFalse(operation.is_order_dependent)
         self.assertFalse(operation.is_count_dependent)
 
+    def test_min_max_rows(self) -> None:
+        """Test min and max rows for edge-case deduplications."""
+        self.assertEqual(self.leaf.with_only_columns(set()).without_duplicates().min_rows, 1)
+        self.assertEqual(self.leaf.with_only_columns(set()).without_duplicates().max_rows, 1)
+        leaf0 = self.engine.make_leaf({self.a}, payload=iteration.RowSequence([]), name="leaf")
+        self.assertEqual(leaf0.without_duplicates().min_rows, 0)
+        self.assertEqual(leaf0.without_duplicates().max_rows, 0)
+        self.assertEqual(leaf0.with_only_columns([]).without_duplicates().min_rows, 0)
+        self.assertEqual(leaf0.with_only_columns([]).without_duplicates().max_rows, 0)
+
     def test_backtracking_apply(self) -> None:
         """Test apply logic that involves reordering operations in the existing
         tree to perform the new operation in a preferred engine.