You are right along with the others, the seq scan was only forced because of
the varchar-text comparision.. Using the cast solves the problem.
Thanks for the answers everyone!
Balazs
-----Original Message-----
From: Fernando Hevia [mailto:fhevia@ip-tel.com.ar]
Sent: Tuesday, January 05, 2010 3:16 PM
To: 'Keresztury Balázs'; pgsql-performance@postgresql.org
Subject: RE: [PERFORM] forced sequential scan when condition has
current_user
> -----Mensaje original-----
> De: Keresztury Balázs
>
> hi,
>
> just a small question: is it normal that PostgreSQL 8.4.1
> always uses sequential scanning on any table when there is a
> condition having the constant "current_user"? Of course there
> is a btree index set on that table, but the DBMS just doesn't
> want to utilize it. When I replace current_user to any
> string, the planner uses the index normally.
>
> I can demonstrate it with the following simple query:
>
> SELECT psz.kotesszam FROM projekt.projektszervezet psz WHERE
> psz.felhasznalo_id = current_user;
>
Probably you are comparing different types. Try explicitly casting
current_user to text:
SELECT psz.kotesszam FROM projekt.projektszervezet psz WHERE
psz.felhasznalo_id = current_user::text
