Re: statement_cost_limit

I can see this as useful for newbies who don't want to accidentally
overload the system.

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Simon Riggs wrote:
> On Wed, 2006-03-01 at 11:47 -0500, Tom Lane wrote:
> > Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> > > A new parameter that allows the administrator to place sensible limits
> > > on the size of queries executed.
> >
> > As I said when the idea was floated originally, I don't think this is a
> > very good idea at all. The planner's estimates are sufficiently often
> > wrong that refusing to execute queries on the strength of an estimated
> > cost is going to burn you in both directions.
>
> That depends upon your view on risk. Some admins would rather abort a
> few queries wrongly in less than a second than risk having a query run
> for hours before being cancelled by statement_timeout. Most end-users
> would agree with this, because if the answer is No they want to hear it
> quickly so they can correct their mistake and continue.
>
> But I think the estimates aren't sufficiently wrong to make a big
> difference. People with a 100GB+ table can set it with sufficiently
> useful accuracy to avoid pointless attempts to sort that table, for
> example.
>
> > Even if it were a good idea, the proposed location of the test is 100%
> > wrong, as you are only guarding one path of query submission. Or were
> > you intending that the restriction be trivial to subvert?
>
> The main idea was to guard the path by which ad-hoc queries would come,
> but you might want to set it on a dev server also for example.
>
> Its a discussion point as to whether we'd want it the way I've coded, or
> whether you want to block other routes also. I can see things both ways
> on that and have no problem changing the behaviour if that is the
> consensus; that change would be fairly quick.
>
> Best Regards, Simon Riggs
>
>
>
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SRA OSS, Inc. http://www.sraoss.com

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