From: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org, pgsql-patches(at)postgresql(dot)org |
Subject: | Re: [HACKERS] Reducing the overhead of NUMERIC data |
Date: | 2005-11-02 23:28:25 |
Message-ID: | 20051102232825.GY55520@pervasive.com |
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Lists: | pgsql-hackers pgsql-patches |
On Wed, Nov 02, 2005 at 06:12:37PM -0500, Tom Lane wrote:
> Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> > It seems straightforward enough to put in an additional test, similar to
> > the ones already there so that if its too big for a decimal we make it a
> > float straight away - only a float can be that big in that case. After
> > that I can't really see what the problem is?
>
> Wrong answer. You'll be introducing weird corner cases into the type
> resolution behavior.
>
> An approach that would actually have some credibility would be to not
> resolve constants to NUMERIC right away, but to invent an UNKNOWNNUMERIC
> pseudotype with coercion behavior comparable to the existing UNKNOWN
> type for string literals. This has been proposed before but hasn't
> really been needed so far. Of course, this converts the project from a
> minor localized hack on NUMERIC into a major piece of fiddling with the
> type resolution rules, with the potential for unforeseen side-effects on
> the behavior of other data types. It might be worth doing anyway --- I
> don't recall at the moment what problems UNKNOWNNUMERIC was intended to
> solve, but if they're still open issues then it's something we ought to
> get around to sometime.
Thought I'd look to see if I could find anything about UNKNOWNNUMERIC,
but no such luck (ISTM we really need a better way to find discussion on
old ideas...) But while looking I did find this TODO, which might be
relevant to the current discussion:
# Change NUMERIC to enforce the maximum precision, and increase it
Unfortunately I can't find any reference to that in the archives...
--
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
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