Re: vacuum internals and performance affect

MirrorX,

> so when a transaction is still open from a while back (according to the
> transactionID), no 'new dead' tuples can be marked as re-usable space for
> new rows, right? by 'new dead' i mean that for example there is a
> transaction running from 10.00am(with a specific transactionID). when i
> delete rows at 11.00am these are the ones i am referring to.

With the understanding that what we're actually checking is snapshots
(which are not completely linear) and not timestamps, yes, that's a good
simplification for what happens.

> but, for these rows, the 'deleted' ones. does vacuum do anything at all at
> that time? and if so, what is it? thx in advance

No, it does nothing.  What would it do?

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com