Re: Finding out if 'vacuum --analyze-in-stages' has generated enough stats

On Wed, Mar 31, 2021 at 6:46 PM Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>
> On Wed, Mar 31, 2021 at 12:38:14PM +0530, Vineet Naik wrote:
> > > This option will try to create some statistics as fast as possible, to make the database usable, and then produce full statistics in the subsequent stages.
> >
> > So my question is, after which stage is it ok to send traffic to the
> > server without much performance impact? Also, is it possible to query
> > the stats view in pg and determine if enough stats have been
> > generated?
>
> That is a very hard question to answer. Some queries have only a few
> possible plans, so few or no statistics are fine. Other queries require
> detailed statistics to generate efficient plans. I think you need to
> set up a dummy server with no stats and try your workload on that, then
> run the stages manually and test after each stage to see how the
> performance is.

That's a good idea. And it should be easily doable as we already have
a dummy server and there are only 2 tables of concern.

Thanks,
Vineet