Re: serial type; race conditions

How does currval work if you are not inside a transaction. I have
been experimenting with inserting into a table that has a sequence.
If the insert fails (not using a transaction) because of bad client input
then the next insert gets the proper next number in the sequence.

given sequence 1,2,3,4,5 exists
insert into table date 1/111/01 (obviously wrong) insert fails...
try again with good data, insert succeeds and gets number 6 in the
sequence.

i'm getting what I want. A sequence number that does not increment
on a failed insert. However, how do I get the assigned sequence
number with currval when I am not using a transaction? What
happens when multiple users are inserting at the same time?

I am trying to create a sequence with out any "missing" numbers. If
there is a failure to insert, and a sequence number is "taken". I want
the empty row.

Thanks, .... it is getting clearer....

Ted

-----Original Message-----
From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: jkakar(at)expressus(dot)com
Date: Mon, 26 Mar 2001 16:47:37 -0500 (EST)
Subject: Re: [SQL] serial type; race conditions

> > Hi,
> >
> > I'm using serial fields to generate IDs for almost all object in my
> > database. I insert an empty row, get the CURRVAL() of the
sequence
> > and then update to that value.
> >
> > I had understood (and now, I can't find the reference to back this
> up)
> > that serial is implemented in such a way that race conditions
between
> > DB connections can't happen.
> >
> > Is this true?
>
> Safe. See FAQ item. currval is for your backend only.
>
> --
> Bruce Momjian | http://candle.pha.pa.us
> pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
> + If your life is a hard drive, | 830 Blythe Avenue
> + Christ can be your backup. | Drexel Hill, Pennsylvania
> 19026
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