Re: [SQL] abusing an aggregate funct

On Sun, 15 Nov 1998, Postgres DBA wrote:

>
>
> On Sun, 15 Nov 1998, M Simms wrote:
>
> > > Unfortunately, solution using sequences is not so good unless you don't
> > > suppose to use access to that table from some simultaneously running
> > > sessions. The problem is that every sessions accessing this additional
> > > sequence  with nextval()  will get its own pool of values for the
> > > sequence, so early or later you'll get some gaps in records numbering
> > > because of at least on of two reasons:
> >
> > >From the manpage of create sequence
> >
> >
> >        Low-level locking is used to enable multiple  simultaneous
> >        calls to a generator.
> >
> > Doesnt this mean it will work for this task?
> >
> >
>
> Sure, you can access one sequence from a couple of sessions at once but
> it the only thing is guaranteed is UNIQUENESS of values you get from
> nestval() across one sequence. Although nobody can promise you that there
> will no gaps... There are lots of reasons, I mentioned just some of them
> (see my previous posting in this thread)
>
> Aleksey
>
>
>
>

My understanding is that if you do not enable the cache feature
of the sequence, there will be no gaps.  Of course, disabling the
cache slows the transaction.

Marc Zuckman
marc@fallon.classyad.com

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