On Wednesday 18 April 2007 10:41, Joe Brown wrote:
> Oracle, Postgeres and possible other databases use sequences for
> sequential number generation for pk type scenarios. Postgresql has
> added the serial/bigserial datatypes which use triggers for
> autoincrementing the serial columns. But this still requires a select
> statement to acquire the inserted value.
>
> In the past you had/have to select nextval('my_sequence') prior to
> inserting. The populate the pk field with the value and perform the
> insert, or write your own triggers.
>
> We can select curval('my_sequence') form the database to determine the
> value last retrieved from the most recent trigger auto-population of
> serial datatype, however, this requires a sequence name be known.
> Although this can be determined progmatically, I'd like to be able to
> manually set the sequence name property for the pk field and have select
> nextval('my_sequence') sql executed to populate the pk filed, prior to
> the insert.
lastval
Return the value most recently returned by nextval in the current session.
This function is identical to currval, except that instead of taking the
sequence name as an argument it fetches the value of the last sequence that
nextval was used on in the current session. It is an error to call lastval if
nextval has not yet been called in the current session.
> The argument might be that this can be handled by hand in the newrecord
> method. This however, is often used for both databases, so I think it
> would be prudent to add a 'sequence' type property to the bizobject and
> incorporate population of the pk filed via the sequence.
>
> The bizObject would then store the last inserted pk value for later
> reference by child records.
>
> -Joseph
I'm not sure I agree. I can see advantages but surely not all DB's work the
same as Postgres and Oracle. In the case of FireBird sequences work
differently (UWE might provide more info). And for the moment I don't see
why dabo's cursor.lastrowid() wouldn't meet most expectations.
Currently, dabo's cursor.lastrowid() returns OID's but I'll be changing that
real soon.
--
John Fabiani
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