Re: Routine maintenance - vacuum, analyse and autovacuum

"Iain" <iain(at)mst(dot)co(dot)jp> writes:
>> Just moving from 7.1 to 7.4 should help, since you can start using plain
>> vacuum (7.1's vacuum is equivalent to vacuum full IIRC).

> That old DB server has been running contnuously for 2 years they tell me.
> Apparently it is also growing despite nightly vacuums and a stable data set
> size (old data is purged dai.ly and monthly). Nightly delete/insert batches
> and vacuums are taking longer and longer too. I suspect the vacuum isn't
> doing what they think - possibly due to the FSM being at the default, and
> possibly due to ghost processes holding old record versions open. It has
> been stable nonetheless. Anyway, I'm sure we can do much better in 7.4.

Kinda sounds like index bloat to me --- have you done any looking to
determine which files are growing?

> OK, that's the kind of thing I wanted to know. Basically, partial runs of
> vacuum full are not likely to be of any benefit. So, unless you intend to
> let it run to completion, best to avoid it.

Right.

> Given that our system experiences quite heavy usage during the day, and has
> a nightly window for batch processing I'm wondering if the best way to go
> about this is to give auto vacuum a miss and just do a standard vacuum after
> the batch processes have completed. As long as the FSM is big enough to
> handle the amount of data changed in 1 day, it would be OK, right?

Yes, though plain VACUUM is not as much of a drag on performance as
VACUUM FULL (== 7.1 VACUUM). So you might want to experiment and
see if you can get away with it during the day. Also note there is work
afoot to reduce the VACUUM performance drag even further in 7.5.

regards, tom lane