Re: Performance weirdness with/without vacuum analyze

Shridhar Daithankar writes:
> Harry Broomhall wrote:
> > #effective_cache_size = 1000 # typically 8KB each
> > #random_page_cost = 4 # units are one sequential page fetch cost
>
> You must tune the first one at least. Try
> http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html to tune these
> parameters.

Wow. Many thanks for the pointer. I'm going to be spending some time
trying to get my head around all of that!

[SNIP]

> > Total runtime: 80408.42 msec
> > (12 rows)
>
> You are lucky to get a better plan here because planner is way off w.r.t
> estimated number of rows.

Yes! I thought that. Which was why I was so surprised at the difference.

> >
> > And now the case *with* the vacuum analyze:
> >
[SNIP]
>
> What happens if you turn off hash joins? Also bump sort memory to something
> good.. around 16MB and see what difference does it make to performance..

Lots of things to try there.....

It will probably take me some time <grin>.

Regards,
Harry.