Jim C. Nasby wrote:
> On Wed, Dec 21, 2005 at 05:43:38PM -0500, Bruce Momjian wrote:
> > Rick Gigger wrote:
> > > It seems to me like there are two classes of problems here:
> > >
> > > 1) Simply invalidating plans made with out of date statistics.
> > > 2) Using run-time collected data to update the plan to something more
> > > intelligent.
> > >
> > > It also seems like #1 would be fairly straightforward and simple
> > > whereas #2 would be much more complex. #1 would do me a world of
> > > good and probably other people as well. Postgres's query planning
> > > has always been fine for me, or at least I have always been able to
> > > optimize my queries when I've got a representative data set to work
> > > with. Query plan caching only gets me when the query plan is created
> > > before the statistics are present to create a good plan.
> > >
> > > Just one users 2 cents.
> >
> > Agreed. I just can't add #2 unless we get more agreement from the
> > group, because it has been a disputed issue in the past.
>
> Well, how about this, since it's a prerequisit for #2 and would be
> generally useful anyway:
>
> Track normal resource consumption (ie: tuples read) for planned queries
> and record parameter values that result in drastically different
> resource consumption.
>
> This would at least make it easy for admins to identify prepared queries
> that have a highly variable execution cost.
We have that TODO already:
* Log statements where the optimizer row estimates were dramatically different from the number of rows actually
found?
-- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610)
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