How to list all parameters in Postgres? - database

Question

I was wondering if there's a parameter for the currently authenticated psql user?
But then I wonder a more broader question - how can I just see what all the paremeters are?
I might discover some interesting parameters if I could see a whole list of them?
I'm only seeing online how to get the value of one parameter. Not a list...

Answer 1

Alvaro has answered the question how to list your current parameter values.
To get the authenticated user, you can call the SQL function session_user:
SELECT session_user;
The currently effective user can be seen with
SELECT current_user;
In psql, you can see details about your current database session with
\conninfo

Answer 2

Nonsense. Try these two SQL statements:
set foo.bar =42;
and then:
select current_setting('foo.bar');
You’ve just set, and read an entity that the PostgreSQL doc doesn’t seem to name. You might call x.y a “user-defined session parameter”. Where is its value held? Server-side, of course.
I too would like to know how to list the names of all currently defined such entities—system-defined, like TimeZone, and user-defined.
— bryn#yugabyte.com

Answer 3

PostgreSQL does not have such a thing as server-side session variables, so it's not clear what you are asking about.
Some PLs (such as PL/Python, PL/Perl) have session variables (%_SHARED in PL/Perl, GD and SD in PL/Python for example), but they are internal to the PL, not part of the server proper.
psql also has variables, which you can set with \set, and you can get a list with the same command. I suppose that's not what you want though.
Maybe you refer to so-called custom GUC configuration parameters, which are sometimes abused as session variables. You can get a list of those using SHOW ALL or SELECT * FROM pg_catalog.pg_settings.

Answer 4

SHOW ALL below can show all parameters according to the documentation:
SHOW ALL;
This is how SHOW ALL works below:
postgres=# SHOW ALL;
name | setting | description
----------------------------+-------------+------------------------------------------------------------------------------------------
allow_in_place_tablespaces | off | Allows tablespaces directly inside pg_tblspc, for testing.
allow_system_table_mods | off | Allows modifications of the structure of system tables.
application_name | psql | Sets the application name to be reported in statistics and logs.
archive_cleanup_command | | Sets the shell command that will be executed at every restart point.
archive_command | (disabled) | Sets the shell command that will be called to archive a WAL file.
archive_mode | off | Allows archiving of WAL files using archive_command.
archive_timeout | 0 | Forces a switch to the next WAL file if a new file has not been started within N seconds.
array_nulls | on | Enable input of NULL elements in arrays.
authentication_timeout | 1min | Sets the maximum allowed time to complete client authentication.
autovacuum | on | Starts the autovacuum subprocess.
...
And, you can show one specific parameter with SHOW as shown below:
postgres=# SHOW allow_in_place_tablespaces;
allow_in_place_tablespaces
----------------------------
off
(1 row)
But, you cannot show more than one parameters with SHOW as shown below:
postgres=# SHOW allow_in_place_tablespaces, allow_system_table_mods;
ERROR: syntax error at or near ","
LINE 1: show allow_in_place_tablespaces, allow_system_table_mods;
So to show more than one parameters, use SELECT FROM pg_settings below:
postgres=# SELECT name, setting, short_desc FROM pg_settings WHERE name IN ('allow_in_place_tablespaces', 'allow_system_table_mods');
name | setting | short_desc
----------------------------+---------+------------------------------------------------------------
allow_in_place_tablespaces | off | Allows tablespaces directly inside pg_tblspc, for testing.
allow_system_table_mods | off | Allows modifications of the structure of system tables.
(2 rows)
In addition, current_setting() can show one specific parameter as shown below:
postgres=# SELECT current_setting('allow_in_place_tablespaces');
current_setting
-----------------
off
(1 row)
But, you cannot show more than one parameters with current_setting() as shown below:
postgres=# SELECT current_setting('allow_in_place_tablespaces', 'allow_system_table_mods');
ERROR: invalid input syntax for type boolean: "allow_system_table_mods"
LINE 1: ...ECT current_setting('allow_in_place_tablespaces', 'allow_sys...