| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Greg Stark <stark(at)mit(dot)edu> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, David Rowley <dgrowleyml(at)gmail(dot)com> |
| Subject: | Re: [PATCH] Negative Transition Aggregate Functions (WIP) |
| Date: | 2013-12-15 01:27:21 |
| Message-ID: | 52AD0579.8040807@agliodbs.com |
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| Thread: | |
| Lists: | pgsql-hackers |
On 12/14/2013 05:00 PM, Tom Lane wrote:
> This consideration also makes me question whether we should apply the
> method for NUMERIC. Although in principle numeric addition/subtraction
> is exact, such a sequence could leave us with a different dscale than
> is returned by the existing code. I'm not sure if changing the number of
> trailing zeroes is a big enough behavior change to draw complaints.
If we're going to disqualify NUMERIC too, we might as well bounce the
feature. Without a fast FLOAT or NUMERIC, you've lost most of the
target audience.
I think even the FLOAT case deserves some consideration. What's the
worst-case drift? In general, folks who do aggregate operations on
FLOATs aren't expecting an exact answer, or one which is consistent
beyond a certain number of significant digits.
And Dave is right: how many bug reports would we get about "NUMERIC is
fast, but FLOAT is slow"?
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com
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