BUG #17077: about three parameters in postgresql 13.3

The following bug has been logged on the website:

Bug reference: 17077
Logged by: yanliang lei
Email address: leiyanliang(at)highgo(dot)com
PostgreSQL version: 13.3
Operating system: CentOS7.6
Description:

Three parameters are
'transaction_deferrable','transaction_isolation','transaction_read_only'。

in the following sql statement,there are three
parameters（'transaction_deferrable','transaction_isolation','transaction_read_only'）

[pg133(at)VM-0-8-centos ~]$ psql -d postgres
psql (13.3)
Type "help" for help.

postgres=# select * from pg_settings where name in
('transaction_deferrable','transaction_isolation','transaction_read_only');
name | setting | unit |
category |
short_desc |
extra_desc | c
ontext | vartype | source | min_val | max_val |
enumvals | boot_val | reset_val
| sourcefile | sourceline | pending_restart
------------------------+----------------+------+-------------------------------------------------+-------------------------------------------------------------------------------------------------------------------------+------------+--
-------+---------+----------+---------+---------+----------------------------------------------------------------------+----------------+----------------+------------+------------+-----------------
transaction_deferrable | off | | Client Connection Defaults
/ Statement Behavior | Whether to defer a read-only serializable transaction
until it can be executed with no possible serialization failures. |
| u
ser | bool | override | | |
| off | off
| | | f
transaction_isolation | read committed | | Client Connection Defaults
/ Statement Behavior | Sets the current transaction's isolation level.
|
| u
ser | enum | override | | | {serializable,"repeatable
read","read committed","read uncommitted"} | read committed | read committed
| | | f
transaction_read_only | off | | Client Connection Defaults
/ Statement Behavior | Sets the current transaction's read-only status.
|
| u
ser | bool | override | | |
| off | off
| | | f
(3 rows)

postgres=#

in the
https://www.postgresql.org/docs/current/runtime-config-client.html#RUNTIME-CONFIG-CLIENT-STATEMENT

there is no description about these three parameters。