Re: PG Admin

>
> ----- Original Message -----
> From: "Berend Tober" <btober@seaworthysys.com>
> To: "Bob Pawley" <rjpawley@shaw.ca>
> Cc: "pgsql general" <pgsql-general@postgresql.org>
> Sent: Monday, December 04, 2006 7:15 PM
> Subject: Re: [GENERAL] PG Admin
>
> > Bob Pawley wrote:
> >> Your missing the point.
> >>
> >> I am creating a design system for industrial control.
> >>
> >> The control devices need to be numbered. The numbers need to be
> >> sequential. If the user deletes a device the numbers need to regenerate
> >> to again become sequential and gapless.
> >
> > Could you explain what it is about industrial control that requires the
> > reassignment of numbers? Seems to me to make for confusion because over
> > time, you then have a particular instrument referred to by different
> > identifiers. So if you had other data, such as written logs, shop floor
> > design diagrams, or other data not included in the data base, for
> > example, you'ld have the problem of keeping track of which instruments
> > were really being talked about because the names (identifying number,
> > that is) keep changing.
>
> ---------------------------(end of broadcast)---------------------------
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On Monday 04 December 2006 07:39 pm, Bob Pawley wrote:
> I am talking about designing the control system.
>
> No one makes a perfect design at first go. Devices are deleted and others
> added. Until the end of the design stage the numbers need to be sequential
> with no gaps. After the design the numbers of each device are static and
> new devices are added to the sequence or fill in for abandoned devices -
> but that is another, separate problem.
>
> But that is beside the point. What I am looking for is a gapless sequence
> generator which has the ability to justify for deletions as well as
> additions.
>
> What I am looking for is a very simple adaptation of the serial function.
> All that I need it to do is to justify for design changes and not care that
> if it is reassinged to a different device. The fact that a particular
> device may, by happenstance, change it's assigned number - once twice or
> multiple times, during the design stage,  is of no consequence - as long as
> the totallity of numbers assigned are sequential and gapless.
>
> Bob
>
I see now. My thought would to hold the device numbers in a regular integer
column. Have an AFTER INSERT/UPDATE/DELETE trigger that does a count on the
table and renumbers all  the rows in the id column. This is the brute force
method. The alternative would be to search for the gaps and renumber from the
first gap up.


--
Adrian Klaver
aklaver@comcast.net