Thread: pg_get_databasebyid(oid)

Hello
We already have function pg_get_userbyid(oid) with lookup in pg_authid catalog. My collegue ask me can we add similar
functionpg_get_databasebyid(oid) with lookup in pg_databases.
 
It is simple function to get a database name by oid and fallback to 'unknown (OID=n)' if missing.

The proposed patch is attached. Currently I missed the tests - I doubt which file in src/test/regress/sql/ is the most
suitable.pg_get_userbyid is called from privileges.sql only.
 

regards, Sergei

> Please add that to commitfest.

Done: https://commitfest.postgresql.org/24/2261/

regards, Sergei

Hello

> Is there a need for this function for the user?

This was feature request from user. I got such comment:

This function is useful when working with pg_stat_statements. For obtaining a databаse name for particular query you
needto join pg_database relation, but for obtaining an username you just need pg_get_userbyid(). So it will be useful
notto join extra relation and get a database name using the similar function - pg_get_databasebyid().
 

regards, Sergei

On Thu, Aug 29, 2019 at 03:47:40PM +0500, Ibrar Ahmed wrote:
> I think its a user request and don't require to be in the core of
> PostgreSQL.
> A simple SQL function can fulfill the requirement of the user.
>
> CREATE OR REPLACE FUNCTION pg_get_databasebyid(dboid integer) RETURNS name
> AS $$
>
>     SELECT datname from pg_database WHERE oid = dboid;
> $$ LANGUAGE SQL;

Indeed, I think that we can drop the patch.  FWIW, I find the
semantics of pg_get_userbyid() horrible when it comes to return a
result for a non-existing user with its own way of defining how this
information should show up.  Returning NULL would be more natural, so
I don't think that we should make more functions behave the same way.
--
Michael

Hello

Thank you for attention! I marked CF entry as returned with feedback.

regards, Sergei