Re: arbitrary number of values from a sequence

Ok. I'm looking for another solution.

The reason why I'm not dealing with sequence's increment is that
there is no way to set an appropiate limit, sometimes I need 5, sometimes 17.

Thanks for your help,


Papp Gyozo
- pgerzson@freestart.hu

----- Original Message -----
From: "Tom Lane" <tgl@sss.pgh.pa.us>
To: "Gyozo Papp" <pgerzson@freestart.hu>
Cc: <pgsql-general@postgresql.org>
Sent: 2001. május 4. 20:26
Subject: Re: [GENERAL] arbitrary number of values from a sequence


> "Gyozo Papp" <pgerzson@freestart.hu> writes:
> > Does it mean that it can't be ensured that returning values of
> > nextval() are consecutive ones?
>
> I think it would be folly to assume that, even with a cache setting
> equal to the number of values you intend to fetch.  If the cache gets
> out of sync with your requests (say, because a transaction aborted after
> fetching just some of the 5 values) then subsequent transactions would
> reload the cache partway through, and in that case you could get
> non-consecutive results.
>
> > does it help me if I set the transaction isolation level to
> > serializable or lock the table of the sequence?
>
> No.  Why do you need such a thing, anyway?  If you are always allocating
> groups of 5 IDs, why don't you just pretend each nextval() gives you
> five items instead of one?  You could simply multiply the returned value
> by 5.  Or set the sequence's increment to 5.
>
> regards, tom lane