Re: maintenance_work_mem and autovacuum

On Thu, 2009-03-26 at 19:46 +0100, Guillaume Smet wrote:
> On Thu, Mar 26, 2009 at 7:34 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> > Why do we have separate parameters for autovacuum and vacuum, except for
> > maintenance_work_mem?
> >
> > Should we also have autovacuum_work_mem?
> 
> We already discussed it here:
> http://archives.postgresql.org/message-id/49353A69.20001@hagander.net
> 
> It resulted in a doc patch - not sure it's sufficient but it's
> interesting to read this thread before discussing further.

Hmmm, OK, read that, thanks. Must have missed that thread earlier.

Tom was asking for evidence of a need for them to be different. I don't
see it as a case that requires performance results.

I agree with Magnus' original reasoning: we can have more than one
autovacuum process, so we may have autovacuum_max_workers active and so
the work mem they use must be smaller. For maintenance_work_mem we would
typically only have one session using it at any time, so we either have
to start hardcoding the value in scripts or accept the fact it has been
set lower.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support