Thread: RE: [GENERAL] Sequences : getting back the nextval() result on an insert

Or you could use transactions.
        -DEJ

> -----Original Message-----
> From:    Marin D [SMTP:marin@cybernet.bg]
> Sent:    Thursday, June 11, 1998 5:42 AM
> To:    wstotts@worldnet.att.net
> Cc:    pgsql-general@postgreSQL.org
> Subject:    Re: [GENERAL] Sequences : getting back the nextval()
> result on an insert
>
>
>
> On Thu, 11 Jun 1998, Wim Ceulemans wrote:
>
> > Hi
> >
> > I am new to this list, but I've carefully searched the archives
> before posting this question.
> >
> > I am using JDBC to access postgreSQL 6.3.
> >
> > If one inserts records using a sequence to generate an
> auto-increment primary key, then you can get back the result by using
> "select currval('seq')". There is always a time between the insert and
> the select to retrieve the newly created primary key. Wh
> at I do in my application is insert a record and display it in a java
> swing JTable (including the primary key).
> >
> > How can I be certain that the primary key I retrieve with select
> currval('seq') is the one just inserted? Because in heavily loaded
> multi-user systems someone else can insert a record in the same table
> between my insert and my select.
> >
>
> Actually, as each user spawns a new copy of the backend u can be sure
> that
> currval() gives correct answer as it uses it's backend information.
> I.e
> nextval() and curval() called sequently from the same
> process/application
> will refer to their backend.
>
> If u look at the create secuence schema dump (pg_dump -s XXX) u will
> see
> the CACHE parameter which AFAIK referes to the pool of sequence
> numbers
> alocated per backend.
>
> Hope this helps...
>
>     Marin
>
>
>           -= Why do we need gates in a world without fences? =-