Re: Really really slow select count(*)

On Sun, Feb 6, 2011 at 12:19 PM, Pierre C <lists@peufeu.com> wrote:
>
>>> I have clustered that table, its still unbelievably slow.
>>
>> Did you actually delete the old entries before clustering it?  if it's
>> still got 4G of old sessions or whatever in it, clustering ain't gonna
>> help.
>
> Also, IMHO it is a lot better to store sessions in something like memcached,
> rather than imposing this rather large load on the main database...
>
> PS : if your site has been down for 6 hours, you can TRUNCATE your sessions
> table...

Agreed.  When I started where I am sessions were on pg and falling
over all the time.  Because I couldn't change it at the time, I was
forced to make autovac MUCH more aggressive.  I didn't have to crank
up fsm a lot really but did a bit. Then just ran a vacuum full /
reindex across the sessions table and everything was fine after that.
But we could handle 100x time the load for sessions with memcached I
bet.