Re: BUG #14393: Querry plan creation time is too long

On Mon, Oct 24, 2016 at 6:04 AM, <ufaowl@gmail.com> wrote:

> The following bug has been logged on the website:
>
> Bug reference:      14393
> Logged by:          Vadim Akbashev
> Email address:      ufaowl@gmail.com
> PostgreSQL version: 9.5.4
> Operating system:   Centos 6.8
> Description:
>
> Hello!
> I have two questions concerning choosing\creation time of querry plan
> regaring default_statistic_target parameter. I noticed that querry plan
> creation time increases when default_statistic_target is more than 1000. It
> reaches 14 sec for database without any load when default_statistic_target
> =
> 10 000.
> I wonder:
> 1) Is such behavior considered normal? If it is, where I can get
> documentation regulating this?
>

It is normal that increasing default_statistic_target will increase
planning time.  Increasing it to 14 seconds is undesirable, of course, but
without seeing the query it is hard to say more than that.  This could be a
bug which leads to pathologically slow planning in some cases, or it could
be that your query is just a monster query that is difficult to plan.


2) Is there any way to limit querry plan creation time?
>

See the *_collapse_limit settings here,
https://www.postgresql.org/docs/9.5/static/runtime-config-query.html

And see the further sections referred to from there.

Cheers,

Jeff