Re: Combining Aggregates

On 20 January 2016 at 05:58, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> > On Mon, Dec 21, 2015 at 4:02 AM, David Rowley
> > <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
> >> Now, there has been talk of this previously, on various threads, but I
> don't
> >> believe any final decisions were made on how exactly it should be done.
> At
> >> the moment I plan to make changes as follows:
>
> Oh, one more point: is there any reason why all of this needs to be a
> single (giant) patch? I feel like the handling of internal states
> could be a separate patch from the basic patch to allow partial
> aggregation and aggregate-combining, and that the latter could be
> committed first if we had a reasonably final version of it. That
> seems like it would be easier from a review standpoint, and might
> allow more development to proceed in parallel, too.

I didn't ever really imagine that I'd include any actual new combinefns or
serialfn/deserialfn in this patch. One set has of course now ended up in
there, I can move these off to the test patch for now.

Did you imagine that the first patch in the series would only add the
aggcombinefn column to pg_aggregate and leave the aggserialfn stuff until
later? I thought it seemed better to get the infrastructure committed in
one hit, then add a bunch of new combinefn, serialfn, deserialfns for
existing aggregates in follow-on commits.

--
David Rowley http://www.2ndQuadrant.com/
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