let get_display_size = function
| SQL_db.TinyInt (iopt, _)
| SQL_db.MediumInt (iopt, _)
| SQL_db.Int (iopt, _)
| SQL_db.BigInt (iopt, _)
-> iopt
| SQL_db.Double (opt, _)
| SQL_db.Float (opt, _)
| SQL_db.Decimal (opt, _)
-> Dbf_misc.apply_opt fst opt
| SQL_db.Char i
| SQL_db.VarChar i
-> Some i
| _ -> None