From: | Jakub Wartak <jakub(dot)wartak(at)enterprisedb(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Damage control for planner's get_actual_variable_endpoint() runaway |
Date: | 2022-11-21 16:06:16 |
Message-ID: | CAKZiRmyJuwXoKoCrHiSo0vY5Bs6t6-YK8WNDkUP+Su2voFoCoQ@mail.gmail.com |
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Lists: | pgsql-hackers |
Hi,
Draft version of the patch attached (it is based on Simon's)
I would be happier if we could make that #define into GUC (just in
case), although I do understand the effort to reduce the number of
various knobs (as their high count causes their own complexity).
-Jakub Wartak.
On Mon, Nov 21, 2022 at 4:35 PM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Mon, Nov 21, 2022 at 10:32 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > > Is there any reason to tie this into page costs? I'd be more inclined
> > > to just make it a hard limit on the number of pages. I think that
> > > would be more predictable and less prone to surprising (bad) behavior.
> >
> > Agreed, a simple limit of N pages fetched seems appropriate.
> >
> > > And to be honest I would be inclined to make it quite a small number.
> > > Perhaps 5 or 10. Is there a good argument for going any higher?
> >
> > Sure: people are not complaining until it gets into the thousands.
> > And you have to remember that the entire mechanism exists only
> > because of user complaints about inaccurate estimates. We shouldn't
> > be too eager to resurrect that problem.
> >
> > I'd be happy with a limit of 100 pages.
>
> OK.
>
> --
> Robert Haas
> EDB: http://www.enterprisedb.com
Attachment | Content-Type | Size |
---|---|---|
0001-Damage-control-for-planner-s-get_actual_variable_end.patch | application/octet-stream | 1.9 KB |
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