Re: RFC: changing autovacuum_naptime semantics

Alvaro Herrera <alvherre@commandprompt.com> writes:
> Now regarding your restartable vacuum work.  I think that stopping a
> vacuum at some point and being able to restart it later is very cool and
> may get you some hot chicks, but I'm not sure it's really useful.

Too true :-(

> I think it makes more sense to do something like throttling an ongoing
> vacuum to a reduced IO rate, if the maintenance window closes.  So if
> you're in the middle of a heap scan and the maintenance window closes,
> you immediately stop the scan and go the the index cleanup phase, *at a
> reduced IO rate*.

Er, why not just finish out the scan at the reduced I/O rate?  Any sort
of "abort" behavior is going to create net inefficiency, eg doing an
index scan to remove only a few tuples.  ISTM that the vacuum ought to
just continue along its existing path at a slower I/O rate.
        regards, tom lane