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.