Re: TODO : Allow parallel cores to be used by vacuumdb [ WIP ]

On Fri, Oct 17, 2014 at 1:31 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>
> On 16 October 2014 15:09, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> > I think doing anything on the server side can have higher complexity
like:
> > a. Does this function return immediately after sending request to
> > autovacuum, if yes then the behaviour of this new functionality
> > will be different as compare to vacuumdb which user might not
> > expect?
> > b. We need to have some way to handle errors that can occur in
> > autovacuum (may be need to find a way to pass back to user),
> > vacuumdb or Vacuum can report error to user.
> > c. How does nworkers input relates to autovacuum_max_workers
> > which is needed at start for shared memory initialization and in calc
> > of maxbackends.
> > d. How to handle database wide vacuum which is possible via vacuumdb
> > e. What is the best UI (a command like above or via config parameters)?
>
>
> c) seems like the only issue that needs any thought. I don't think its
> going to be that hard.
>
> I don't see any problems with the other points. You can make a
> function wait, if you wish.

It is quite possible, but still I think to accomplish such a function,
we need to have some mechanism where it can inform auto vacuum
and then some changes in auto vacuum to receive/read that information
and reply back. I don't think any such mechanism exists.

> > I think we can find a way for above and may be if any other similar
things
> > needs to be taken care, but still I think it is better that we have this
> > feature
> > via vacuumdb rather than adding complexity in server code. Also the
> > current algorithm used in patch is discussed and agreed upon in this
> > thread and if now we want to go via some other method (auto vacuum),
> > it might take much more time to build consensus on all the points.
>
> Well, I read Alvaro's point from earlier in the thread and agreed with
> it. All we really need is an instruction to autovacuum to say "be
> aggressive".
>
> Just because somebody added something to the TODO list doesn't make it
> a good idea. I apologise to Dilip for saying this, it is not anything
> against him, just the idea.
>
> Perhaps we just accept the patch and change AV in the future.

So shall we move ahead with review of this patch and make a note
of changing AV in future (may be TODO)?

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com