Re: problem with from_collapse_limit and joined views

Markus Schulz  11/24/10 1:02 PM >>>

> if i set "from_collapse_limit" (to merge the views) and
> join_collapse_limit (to explode the explicit joins) high enough
> (approx 32), all is fine (good performance). But other queries are
> really slow in our environment (therefore it's no option to raise
> the join_collapse_limit to a higher value)
>
> With defaults (8) for both, the performance is ugly

One option would be to create a different user for running queries
which read from complex views such as this.

postgres=# create user bob;
CREATE ROLE
postgres=# alter user bob set from_collapse_limit = 40;
ALTER ROLE
postgres=# alter user bob set join_collapse_limit = 40;
ALTER ROLE

Log in as bob, and your queries should run fine.

Nothing leapt out at me as an issue in your postgresql.conf except:

max_prepared_transactions = 20

Do you actually use prepared transactions?  (Sometimes people confuse
this with prepared statements, which are a completely different
feature.)

-Kevin