Fix bugs

Author: methane

src/MySQLdb/_mysql.c

@@ -2114,18 +2114,25 @@ _mysql_ConnectionObject_discard_result(
     MYSQL *conn = &(self->connection);
 
     Py_BEGIN_ALLOW_THREADS;
+
     MYSQL_RES *res = mysql_use_result(conn);
     if (res == NULL) {
         Py_BLOCK_THREADS;
-        return _mysql_Exception(self);
+        if (mysql_errno(conn) != 0) {
+            // fprintf(stderr, "mysql_use_result failed: %s\n", mysql_error(conn));
+            return _mysql_Exception(self);
+        }
+        Py_RETURN_NONE;
     }
+
     MYSQL_ROW row;
     while (NULL != (row = mysql_fetch_row(res))) {
         // do nothing.
     }
     mysql_free_result(res);
     Py_END_ALLOW_THREADS;
     if (mysql_errno(conn)) {
+        // fprintf(stderr, "mysql_free_result failed: %s\n", mysql_error(conn));
         return _mysql_Exception(self);
     }
     Py_RETURN_NONE;

src/MySQLdb/cursors.py

@@ -90,7 +90,7 @@ def _discard(self):
         con = self.connection
         if con is None:
             return
-        while con.next_result():
+        while con.next_result() == 0:  # -1 means no more data.
             con.discard_result()
 
     def close(self):