Thanks for the explanation.
I think I misunderstood the SET behaviour. It's OK if only my session is affected.
Regards,
Antonio Carlos Furtado
On Mon, Jun 4, 2012 at 6:01 PM, Jeff Davis
<pgsql@j-davis.com> wrote:
On Mon, 2012-06-04 at 17:49 -0300, Antonio Carlos Salzvedel Furtado
Junior wrote:
> Hello PostgreSQL users,
>
> I've been working with the estimated cost from EXPLAIN. I was
> wondering if I could change the tuning parameters, to produce new
> estimated costs, without interfering with the database workload. Is it
> possible?
>
> I'm changing these parameters by executing SQL queries ("SET"). The
> problem is that once I change these parameters, the query optimizer
> will start using these values to build their query plans.
(the session). So this is safe for EXPLAINing queries. If you do a "SET
LOCAL" within a transaction, it will only affect that transaction.
To make the values persist and get picked up by other connections, you
need to set them in postgresql.conf and send a SIGHUP (or restart, of
course).
Regards,
Jeff Davis