DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma;
	h=mime-version:in-reply-to:references:date:message-id:subject:from:to
	:cc:content-type:content-transfer-encoding;
	b=pn49c7qyI+lg6sxY3Iz3CJ7RNu0Vn5qkZq2J34sg2xb5qIbFMCwwnKzZ06Hm/tp9sO
	cvet0U7FAGTO81VBJ/hY7+GkCbfg2enjlaidd8gibt8lXmkrSuXbRQTQE/vZSyofLIku
	RLu1qQRga7iOGk2Ieg9XmbDn2zdAcmawmdajU=
MIME-Version: 1.0
In-Reply-To: <396486430904131418g3898dc5h2472f9efab331489@mail.gmail.com>
References: <49DC1034.1060705@frii.com>
	<dcc563d10904101120y49f00977nc74132e982518444@mail.gmail.com>
	<49E37441.6030301@frii.com>
	<d18085b50904131409g10d43d6cs35dd14ede13bc02@mail.gmail.com>
	<396486430904131418g3898dc5h2472f9efab331489@mail.gmail.com>
Date: Mon, 13 Apr 2009 17:32:53 -0400
Message-ID: <d18085b50904131432o1d3af00ci250d1077024648f5@mail.gmail.com>
Subject: Re: changing multiple pk's in one update
From: Glenn Maynard <glennfmaynard@gmail.com>
To: Richard Broersma <richard.broersma@gmail.com>
Cc: pgsql-sql@postgresql.org
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

On Mon, Apr 13, 2009 at 5:18 PM, Richard Broersma
<richard.broersma@gmail.com> wrote:
>> Your PK is a composite of (entry, order)? =C2=A0Won't your foreign keys
>> elsewhere all break when you shift the order around?
>
> If there really are foreign keys, then an update will not be allowed
> to shift a primary key unless the foreign key is set with ON UPDATE
> CASCADE then the shifts will be cascaded to all references
> automatically.

Right.  I'm still dusting off my SQL after a long period of corrosion.  :)

The same applies, though, if you have external references to the PK;
for example, if you have a web interface where "/sense/10/3" refers to
entry 10, sense 3.  If your senses are reordered by someone else, and
you operate on /10/3, you may suddenly find yourself viewing or
modifying (or deleting!) a different sense.  This could even happen
within the same transaction, if you're not very careful with
locking...

--=20
Glenn Maynard