Lists: | pgsql-novice |
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From: | Raphael Bauduin <raphael(dot)bauduin(at)be(dot)easynet(dot)net> |
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To: | pgsql-novice(at)postgresql(dot)org |
Subject: | setting custom session variables? |
Date: | 2004-11-12 10:20:35 |
Message-ID: | 41948E73.1060504@be.easynet.net |
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Lists: | pgsql-novice |
Hi,
Can I set my own postgresql session variables?
My idea is the following: I have a web based app, working with a postgresql db.
The app connects to the postgresql with user db_user. All users of the web app have to
authenticate with a login and password.
I want to be able to know which "app user" did which database changes. For that, I can
tweak all SQL queries issued to the DB server to set a column 'user' to the logged in user.
I thought that if I could set a session variable, I wouldn't even have to change the queries
but simply use a trigger that simply set the new.user to the corresponding session variable:
pg_session_set('app_user', 'app-user-logged-in');
update customers set name='new_name' where customer_id=123;
This last query fires the trigger that set the user value for customer 123 to
'app-user-logged-in':
CREATE TRIGGER "set_user_customers" before UPDATE on "customers" for each row execute procedure "set_user" ();
CREATE FUNCTION "set_user" () RETURNS opaque AS '
BEGIN
new.user=pg_session_get('app_user');
return new;
END;
' LANGUAGE 'plpgsql';
Is that possible or a good idea to begin with?
I've found doc on predefined session variables (http://www.be.postgresql.org/docs/7.4/static/functions-misc.html#FUNCTIONS-MISC-SESSION-TABLE)
but nothing about user defined session vars.
thanks
Raph
From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Raphael Bauduin <raphael(dot)bauduin(at)be(dot)easynet(dot)net> |
Cc: | pgsql-novice(at)postgresql(dot)org |
Subject: | Re: setting custom session variables? |
Date: | 2004-11-12 15:08:59 |
Message-ID: | 19633.1100272139@sss.pgh.pa.us |
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Lists: | pgsql-novice |
Raphael Bauduin <raphael(dot)bauduin(at)be(dot)easynet(dot)net> writes:
> Can I set my own postgresql session variables?
Not in existing releases. There is a feature in 8.0 that you could
use (or misuse?) that way.
regards, tom lane
From: | Joe Conway <mail(at)joeconway(dot)com> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Raphael Bauduin <raphael(dot)bauduin(at)be(dot)easynet(dot)net>, pgsql-novice(at)postgresql(dot)org |
Subject: | Re: setting custom session variables? |
Date: | 2004-11-12 16:37:30 |
Message-ID: | 4194E6CA.3040901@joeconway.com |
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Lists: | pgsql-novice |
Tom Lane wrote:
> Raphael Bauduin <raphael(dot)bauduin(at)be(dot)easynet(dot)net> writes:
>>Can I set my own postgresql session variables?
>
> Not in existing releases. There is a feature in 8.0 that you could
> use (or misuse?) that way.
>
Also see myfunc_setvar(), myfunc_getvar, and myfunc_rmvar() in:
http://www.joeconway.com/myfunc.tgz
for an example of how you could make your own. There is an article that
briefly describes these functions here:
http://www.onlamp.com/pub/a/onlamp/2004/06/28/postgresql_extensions.html
HTH,
Joe
From: | Raphael Bauduin <raphael(dot)bauduin(at)be(dot)easynet(dot)net> |
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To: | Joe Conway <mail(at)joeconway(dot)com> |
Cc: | pgsql-novice(at)postgresql(dot)org |
Subject: | Re: setting custom session variables? |
Date: | 2004-11-19 10:20:54 |
Message-ID: | 419DC906.6010902@be.easynet.net |
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Lists: | pgsql-novice |
Joe Conway wrote:
> Tom Lane wrote:
>
>> Raphael Bauduin <raphael(dot)bauduin(at)be(dot)easynet(dot)net> writes:
>>
>>> Can I set my own postgresql session variables?
>>
>>
>> Not in existing releases. There is a feature in 8.0 that you could
>> use (or misuse?) that way.
>>
>
> Also see myfunc_setvar(), myfunc_getvar, and myfunc_rmvar() in:
> http://www.joeconway.com/myfunc.tgz
> for an example of how you could make your own. There is an article that
> briefly describes these functions here:
> http://www.onlamp.com/pub/a/onlamp/2004/06/28/postgresql_extensions.html
>
I finally had the time to test it and it does exactly what I need.
That saves us a lot of work, just as tablefunc does.
Thanks a lot!
Raph
>
> HTH,
>
> Joe