On Thu, Dec 21, 2006 at 11:43:27AM -0500, Tom Lane wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> > Tom Lane wrote:
> >> You could make a case that we need *three* numbers: a permanent column
> >> ID, a display position, and a storage position.
> > Could this not be handled by some catalog fixup after an add/drop? If we
> > get the having 3 numbers you will almost have me convinced that this
> > might be too complicated after all.
> Actually, the more I think about it the more I think that 3 numbers
> might be the answer. 99% of the code would use only the permanent ID.
> Display position would be used in *exactly* one place, namely while
> expanding "SELECT foo.*" --- I can't think of any other part of the
> backend that would care about it. (Obviously, client-side code such
> as psql's \d would use it too.) Use of storage position could be
> localized into a few low-level tuple access functions, probably.
> The problems we've been having with the concept stem precisely from
> trying to misuse either display or storage position as a permanent ID.
> That's fine as long as it actually is permanent, but as soon as you
> want to change it then you have problems. We should all understand
> this perfectly well from a database theory standpoint: pg_attribute
> has to have a persistent primary key. (attrelid, attnum) is that key,
> and we can't go around altering a column's attnum without creating
> problems for ourselves.
Is there enough consensus on this to add it to the TODO?
Jim Nasby jim(at)nasby(dot)net
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)
In response to
pgsql-hackers by date
|Next:||From: Jonah H. Harris||Date: 2006-12-30 05:49:19|
|Subject: Re: WITH support|
|Previous:||From: Andrew Dunstan||Date: 2006-12-30 04:39:40|
|Subject: Re: TODO: GNU TLS|
pgsql-patches by date
|Next:||From: Bruce Momjian||Date: 2006-12-30 18:53:25|
|Subject: Re: [HACKERS] [BUGS] BUG #2846: inconsistent and|
|Previous:||From: Jim C. Nasby||Date: 2006-12-30 04:08:04|
|Subject: Re: Load distributed checkpoint|