Re: Meaning of vacuum output

"Jeffrey W. Baker" <jwbaker@acm.org> writes:
> rupert=# vacuum verbose resp_header;
> NOTICE:  --Relation resp_header--
> NOTICE:  Pages 28276: Changed 4, Empty 0; Tup 2437108: Vac 0, Keep
> 2295773, UnUsed 96275.
>         Total CPU 1.79s/0.38u sec elapsed 2.72 sec.
> VACUUM
> rupert=# select count(*) from resp_header;
>  count
> --------
>  141357
> (1 row)

> There's nowhere near 2.437e6 tuples in the table, but the difference
> between Tup and Keep seems to be the number of tuples in the table.  But
> what does this mean?  Are there 2.295e6 deleted tuples hanging around in
> the table?

Kinda looks that way.  Do you have open transactions hanging around that
might still be able to see those tuples?

            regards, tom lane