SELECT lists of single variables

Closes #56

Author: michaelosthege

mcbackend/backends/clickhouse.py

@@ -200,7 +200,9 @@ def _get_row_at(
     ) -> Dict[str, numpy.ndarray]:
         self._commit()
         names = ",".join(var_names)
-        data = self._client.execute(f"SELECT ({names}) FROM {self.cid} WHERE _draw_idx={idx};")
+        # NOTE: The trailing , 👇 is included to get the same signature when len(var_names) == 1.
+        query = f"SELECT ({names},) FROM {self.cid} WHERE _draw_idx={idx};"
+        data = self._client.execute(query)
         if not data:
             raise Exception(f"No record found for draw index {idx}.")
         result = dict(zip(var_names, data[0][0]))

mcbackend/test_backend_clickhouse.py

@@ -255,7 +255,6 @@ def test_insert_draw(self):
         numpy.testing.assert_array_equal(v3, draw["v3"])
         pass
 
-    @pytest.mark.xfail(reason="issue #56")
     def test_get_row_at(self):
         run, chains = fully_initialized(
             self.backend,