Re: Should a DB vacuum use up a lot of space ?

On 8/7/2016 10:26 AM, Philippe Girolami wrote:
> More weirdness this afternoon : the wraparound ERROR showed up again even though I have trouble believing I burned through so many transactions in under a day. But let’s assume I did, here is what I noticed
>
> 1) I vacuumed all other databases. For everyone of those, the age went down to 50M instead of zero. Is that normal ?
> 2) The only database that didn’t work on was template0 (the age did not change). It did work on template1
>
> Should I suspect something fishy going on ?

do you have any long running 'idle in transaction' sessions? these would
show up in pg_stat_activity, you want to look at now()-xact_start to see
the age of the oldest of these. no tuples newer than the oldest
xact_start can be vacuumed.

select * from pg_stat_activity where state='idle in transaction';

select count(*), max(now()-xact_start) from pg_stat_activity where
state='idle in transaction';

--
john r pierce, recycling bits in santa cruz