Re: [HACKERS] Auto-updated fields

On Thu, May 08, 2008 at 08:44:46AM +0200, Martijn van Oosterhout wrote:
> On Wed, May 07, 2008 at 03:04:49PM -0700, David Fetter wrote:
> > 1. Create a generic (possibly overloaded) trigger function,
> > bundled with PostgreSQL, which sets a field to some value. For
> > example, a timestamptz version might set the field to now().
>
> Doesn't the SQL standard GENERATED BY functionality work for this?
> Or won't that handle updates?

It appears to, at least according to 6WD2_02_Foundation_2007-12.pdf :)

4.14.8 Base columns and generated columns

A column of a base table is either a base column or a generated
column. A base column is one that is not a generated column. A
generated column is one whose values are determined by evaluation
of a generation expression, a <value expression> whose declared
type is by implication that of the column. A generation expression
can reference base columns of the base table to which it belongs
but cannot otherwise access SQL data. Thus, the value of the field
corresponding to a generated column in row R is determined by the
values of zero or more other fields of R. A generated column GC
depends on each column that is referenced by a <column reference>
in its generation expression, and each such referenced column is a
parametric column of GC.

Cheers,
David.
--
David Fetter <david@fetter.org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
Skype: davidfetter XMPP: david.fetter@gmail.com

Remember to vote!
Consider donating to Postgres: http://www.postgresql.org/about/donate

--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers