Re: explain plans with information about (modified) gucs

út 1. 1. 2019 v 20:11 odesílatel Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
napsal:

>
>
> On 1/1/19 6:48 PM, Pavel Stehule wrote:
> >
> >
> > út 1. 1. 2019 v 18:39 odesílatel Tomas Vondra
> > <tomas(dot)vondra(at)2ndquadrant(dot)com <mailto:tomas(dot)vondra(at)2ndquadrant(dot)com>>
> napsal:
> >
> > Attached is v4, changing how GUCs are picked for inclusion on the
> query
> > plans. Instead of picking the GUCs based on group and/or explicitly,
> a
> > new GUC_EXPLAIN flag is used for that.
> >
> > I went through GUCs defined in guc.c and marked those in
> QUERY_TUNING*
> > groups accordingly, with the exception of default_statistics_target
> > because that seems somewhat useless without showing the value used to
> > actually analyze the table (and/or columns).
> >
> > I've also included a couple of other GUCs, that I find to be
> relevant:
> >
> > - parallel_leader_participation
> > - max_parallel_workers_per_gather
> > - max_parallel_workers
> > - search_path
> > - effective_io_concurrency
> > - work_mem
> > - temp_buffers
> > - plan_cache_mode
> >
> >
> > when plan_cache_mode is auto, you know maybe too less executed query.
> > Maybe you can read somewhere if plan was custom or generic.
> >
>
> This patch is about showing GUCs, not such additional internal info.
> Also, you'll see the plan actually used.
>

I understand to your goal, and I understand so collecting some data inside
can be hard or impossible.

But if you collect a data important for understanding to planner
behave/decision, then some important information is inside plancache too. -
and now it is not visible from user space.

It is just my note - so not only GUC are interesting - nothing more.

> >
> > I think this covers the interesting GUCs pretty well, although
> perhaps I
> > missed something.
> >
> >
> > seq_page_cost, random_page_cost, from_collapse_limit,
> > join_collapse_limit, ... enable_***
> >
>
> All these GUCs are included, of course.
>

ok - thank you for info.

Regards

Pavel

>
>
>
> --
> Tomas Vondra http://www.2ndQuadrant.com
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>