To: josh@agliodbs.com
Cc: Charles Hauser <chauser@duke.edu>, pgsql-sql@postgresql.org
Subject: Re: problem fetching currval of sequence 
In-reply-to: <200208061135.20799.josh@agliodbs.com> 
References: <web-1602018@davinci.ethosmedia.com>
	<20611.1028651144@sss.pgh.pa.us>
	<200208061135.20799.josh@agliodbs.com>
Comments: In-reply-to Josh Berkus <josh@agliodbs.com>
	message dated "Tue, 06 Aug 2002 11:35:20 -0700"
Date: Tue, 06 Aug 2002 16:18:45 -0400
Message-ID: <2971.1028665125@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Josh Berkus <josh@agliodbs.com> writes:
> No, back in 7.1.0 I was able to call CURRVAL without having previously
> called NEXTVAL, and it would give me the "current" sequence value;
> that is, the same result value as (NEXTVAL() - 1)

I don't believe it, and neither do the 7.1.3 and 7.0.2 databases that
I have handy to check with.  For example:

play=> select version();
                             version
------------------------------------------------------------------
 PostgreSQL 7.0.2 on hppa2.0-hp-hpux10.20, compiled by gcc 2.95.2
(1 row)

play=> create sequence seq;
CREATE
play=> select currval('seq');
ERROR:  seq.currval is not yet defined in this session
play=> select nextval('seq');
 nextval
---------
       1
(1 row)

play=> select currval('seq');
 currval
---------
       1
(1 row)

play=> \c play
You are now connected to database play.
play=> select currval('seq');
ERROR:  seq.currval is not yet defined in this session


Are you sure you were not thinking of "select last_value from seq"?
That's about the closest approximation I can think of to a
non-transaction-safe version of currval().

			regards, tom lane