| From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
|---|---|
| To: | Reece Hart <reece(at)harts(dot)net> |
| Cc: | Decibel! <decibel(at)decibel(dot)org>, Postgres List <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Short-circuiting FK check for a newly-added field |
| Date: | 2008-05-23 22:48:59 |
| Message-ID: | 20080523224859.GF23016@alvh.no-ip.org |
| Views: | Whole Thread | Raw Message | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
Reece Hart wrote:
> On Tue, May 20, 2008 at 02:25:15PM -0400, Decibel! wrote:
> > I need to add a field to a fairly large table. In the same alter statement
> > I'd like to add a FK constraint on that new field. Is there any way to
> > avoid the check of the table that the database is doing right now? The
> > check is pointless because the newly added field is nothing but NULLs.
> >
> I don't see the problem. FK constraints don't fire on NULL values. I
> think you might be imagining that a problem exists when it doesn't.
The problem is that it does a table scan only to find that all values
are NULL, which is pretty pointless.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
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