Surveys cannot be created in batch without `session_code` because it must be unique across surveys. Technically, using a 5-digit codes makes it unlikely that a collision occurs with records created without explicit session_code (see Survey._get_default_session_code's iterative process). See runbot 55709 See also related runbot 25041 solved in #159295 Task-3829536 closes odoo/odoo#162587 X-original-commit: 0efbd6e31f5870c1e3004c129e79b9dfa7379863 Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>