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