Speed up Cursor.fetchall by draining batches directly

pynuodb/cursor.py

@@ -184,7 +184,11 @@ def executemany(self, operation, seq_of_parameters):
     def fetchone(self):
         # type: () -> Optional[result_set.Row]
         """Return the next row of results from the previous SQL operation."""
-        self._check_closed()
+        # Inline _check_closed to avoid per-row function-call overhead.
+        if self.closed:
+            raise Error("cursor is closed")
+        if self.session.closed:
+            raise Error("connection is closed")
         if self._result_set is None:
             raise Error("Previous execute did not produce any results or no call was issued yet")
         self.rownumber += 1
@@ -218,14 +222,22 @@ def fetchall(self):
         # type: () -> List[result_set.Row]
         """Return all rows generated by the previous SQL operation."""
         self._check_closed()
+        if self._result_set is None:
+            raise Error("Previous execute did not produce any results or no call was issued yet")
 
-        fetched_rows = []
+        fetched_rows = []  # type: List[result_set.Row]
         while True:
-            row = self.fetchone()
-            if row is None:
+            # Drain the current in-memory batch in one shot instead of calling
+            # fetchone() per row.
+            idx = self._result_set.results_idx
+            batch = self._result_set.results
+            if idx < len(batch):
+                fetched_rows.extend(batch[idx:])
+                self._result_set.results_idx = len(batch)
+            if self._result_set.complete:
                 break
-            else:
-                fetched_rows.append(row)
+            self.session.fetch_result_set_next(self._result_set)
+        self.rownumber += len(fetched_rows)
         return fetched_rows
 
     def nextset(self):  # pylint: disable=no-self-use