Re: Create roles trigger

Honestly, this is a perfect use-case for calling shell scripts.
________________________________
From: Nasby, Jim <nasbyj(at)amazon(dot)com>
Sent: Friday, October 5, 2018 3:26:22 PM
To: Александр Аникин
Cc: borey2005(at)gmail(dot)com; pgsql-admin(at)postgresql(dot)org
Subject: Re: Create roles trigger

Please do not post to multiple lists. Moving -hackers to BCC.

> On Sep 27, 2018, at 4:07 AM, Александр Аникин <anikin24(at)list(dot)ru> wrote:
>
> Hey, folks!
>
> I've got a question about events on roles creation.
>
> I need to execute some custom logic on role creation.
>
> All information about roles located in `pg_authid` table.
> The first thing that comes to mind is to create trigger on `pg_authid` table, but this is not possible, because this is a system table.
> Next thing, is to create a view (select * from pg_authid) and create trigger on view, but this didn't work out too.

Not sure what you were attempting with the view, but catalog tables are a special case, so those kind of tricks are straight-out not going to work.

> One more thing is to create event trigger (CREATE EVENT TRIGGER trigger ON ddl_command_start WHEN TAG IN ('CREATE ROLE')), but it's also not possible, event triggers are not supported for 'CREATE ROLE'.
>
> Is there is any possibility to do that ? May be, create custom extension or something else.

I would also love to have event triggers for global objects, but unfortunately that’s a very tough nut to crack, because changes to global objects could happen from any database in the entire system (which could easily number in the thousands). For global event triggers to work, there would need to be a global list of event triggers, including which database the event trigger was in. There would also need to be a way to fire those triggers (currently, a backend can not run anything in a separate database). You’d also face the challenge of whether the user running the event trigger had permission to connect to all of those databases.

In short, there’s a lot of work left to be done in order to support what you’re looking for.

BTW, if you only need auditing then you should take a look at pg_audit.

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