table.use_rowid introspection property, closes #285

docs/python-api.rst

@@ -1549,6 +1549,19 @@ The ``.pks`` property returns a list of strings naming the primary key columns f
     >>> db["PlantType"].pks
     ['id']
 
+If a table has no primary keys but is a `rowid table <https://www.sqlite.org/rowidtable.html>`__, this property will return ``['rowid']``.
+
+.. _python_api_introspection_use_rowid:
+
+.use_rowid
+----------
+
+Almost all SQLite tables have a ``rowid`` column, but a table with no explicitly defined primary keys must use that ``rowid`` as the primary key for identifying individual rows. The ``.use_rowid`` property checks to see if a table needs to use the ``rowid`` in this way - it returns ``True`` if the table has no explicitly defined primary keys and ``False`` otherwise.
+
+    >>> db["PlantType"].use_rowid
+    False
+
+
 .. _python_api_introspection_foreign_keys:
 
 .foreign_keys

sqlite_utils/db.py

@@ -809,6 +809,10 @@ class Table(Queryable):
             names = ["rowid"]
         return names
 
+    @property
+    def use_rowid(self):
+        return not any(column for column in self.columns if column.is_pk)
+
     def get(self, pk_values):
         if not isinstance(pk_values, (list, tuple)):
             pk_values = [pk_values]

tests/test_introspect.py

@@ -237,3 +237,11 @@ def test_virtual_table_using(sql, expected_name, expected_using):
     db = Database(memory=True)
     db.execute(sql)
     assert db[expected_name].virtual_table_using == expected_using
+
+
+def test_use_rowid():
+    db = Database(memory=True)
+    db["rowid_table"].insert({"name": "Cleo"})
+    db["regular_table"].insert({"id": 1, "name": "Cleo"}, pk="id")
+    assert db["rowid_table"].use_rowid
+    assert not db["regular_table"].use_rowid