Re: Mini improvement: statement_cost_limit

On Sat, Aug 02, 2008 at 09:30:08PM +0200, Hans-Jürgen Schönig wrote:
> On Aug 2, 2008, at 8:38 PM, Tom Lane wrote:
>
> >Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> >>Hans-Jürgen Schönig wrote:
> >>>i introduced a GUC called statement_cost_limit which can be used to
> >>>error out if a statement is expected to be too expensive.
> >
> >>You clearly have far more faith in the cost estimates than I do.
> >
> >Wasn't this exact proposal discussed and rejected awhile back?
> >
> > regards, tom lane
> >
>
>
> i don't remember precisely.
> i have seen it on simon's wiki page and it is something which would
> have been useful in some cases in the past.

I think a variation on this could be very useful in development and test
environments. Suppose it raised a warning or notice if the cost was over
the limit. Then one could set a limit of a few million on the development
and test servers and developers would at least have a clue that they needed
to look at explain for that query. As it is now, one can exhort them to
run explain, but it has no effect. Instead we later see queries killed
by a 24 hour timeout with estimated costs ranging from "until they unplug
the machine and dump it" to "until the sun turns into a red giant".

-dg

--
David Gould daveg(at)sonic(dot)net 510 536 1443 510 282 0869
If simplicity worked, the world would be overrun with insects.