R: R: slow seqscan after vacuum analize

> ----------------------------------------------------------------------
> > ----------------
> > --------------------
> > Seq Scan on utente (cost=0.00..92174.50 rows=3 width=724) (actual
> > time=705.41..6458.19 rows=15 loops=1)
> > Filter: (luogorilasciodoc = 'ciao'::bpchar) Total
> runtime: 6458.29
> > msec
> > (3 rows
> >
> > Things are worst only for seqscan, when it uses indexscan
> timing is good.
>
> Only thing I can think of is if storage method had been
> changed. Not sure if that would even affect it, or if it
> could do that by itself.
> Just brainstorming.
>

Do you know how can I check if the storage method has changed?
I was thinking that the priority target of a vacuum operation is to reclaim disk space
- this might imply that the performance are worst for a seqscan - maybe it's normal.
Anyway, I am doing a VACUUM FULL ANALYZE right now to see if things get better.

Thanks for you hints
Edoardo