Skip site navigation (1) Skip section navigation (2)

Re: Window-functions patch handling of aggregates

From: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Greg Stark <greg(dot)stark(at)enterprisedb(dot)com>, Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Window-functions patch handling of aggregates
Date: 2008-12-26 19:29:21
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Fri, 2008-12-26 at 14:17 -0500, Tom Lane wrote:
> Greg Stark <greg(dot)stark(at)enterprisedb(dot)com> writes:
> > Yeah, it seems like adding a flag like iswindowable to aggregate  
> > functions is the safest option.

> So the alternatives I see are:
> 1. Go back to Hitoshi's plan of passing WindowAggState to the
> aggregates.  This will require changing every one of the ten aggregates
> in the core distro, as well as every third-party aggregate that has
> a similar optimization; and we just have to keep our fingers crossed
> that anyone who's taking a short-cut will fix their code before it
> fails in the field.
> 2. Use an intermediate dummy AggState as I have in my version, but
> document some convention for telling this from a "real" AggState
> when needed.  (Not hard, we just pick some field that would never be
> zero in a real AggState and document testing that.)  This is certainly
> on the ugly side, but it would very substantially cut the number of
> places that need changes.  Only aggregates that are doing something
> irreversible in their final-functions would need to be touched.
> If we were working in a green field then #1 would clearly be the
> preferable choice, but worrying about compatibility with existing
> third-party aggregates is making me lean to #2.  Comments?
> 			regards, tom lane

I believe the goal should be correctness but why not both? Fix what we
can and put in place a "work around" that would be removed in 8.5?

Joshua D. Drake

   Consulting, Development, Support, Training
   503-667-4564 -
   The PostgreSQL Company, serving since 1997

In response to


pgsql-hackers by date

Next:From: Tom LaneDate: 2008-12-26 19:46:48
Subject: Re: Window-functions patch handling of aggregates
Previous:From: Tom LaneDate: 2008-12-26 19:17:29
Subject: Re: Window-functions patch handling of aggregates

Privacy Policy | About PostgreSQL
Copyright © 1996-2017 The PostgreSQL Global Development Group