After migrating from v7 to Odoo9. Now we are facing speed issue.

Mostly code written in v7 format like:-
mrp_obj = self.pool.get('mrp.production')
for sale in self.browse(cr, uid, ids, context=context):
mo_ids = mrp_obj.search(cr, uid, [('origin','=',sale.name)])
for mo in mrp_obj.browse(cr, uid, mo_ids):
.....
The coding and query style is old in Odoo9 version, is this the speed issue ?? Should I use api.multi tag and re-write the code again ??