Message-Id: <4.1.20000911090110.018637e0@192.168.0.7>
Date: Mon, 11 Sep 2000 09:03:07 +0200
To: Mark Dzmura <mdz@digital-mission.com>,
	"pgsql-interfaces@postgreSQL.org" <pgsql-interfaces@postgreSQL.org>
From: Zeljko Trogrlic <zeljko@technologist.com>
Subject: Re: obtaining primary key/rowid following insert,
  redux...
In-Reply-To: <39B70836.94523C33@digital-mission.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"

nextval() is the solution  to your problems. currval() won't help, all
users will get same previous value.

At 05:15 7.9.2000 , Mark Dzmura wrote:
>Peter:
>
>Trying to solve my problem mentioned in the email of half an hour ago, I 
>searched
>through the archives of the interface list and found some of your replies 
>suggesting
>using "currval()" to get the last value assigned from a sequence...  However,
>here's what happens in a good database with multiple in-use sequences:
>
>db=# select currval('foo_foo_id_seq');
>ERROR:  foo_foo_id_seq.currval is not yet defined in this session
>
>As an alternative, I discovered that I can get the value this way:
>
>db=# select last_value from foo_foo_id_seq;
>last_value
>---------
>              27
>
>My questions are, (1) why does the currval() approach give the error 
>message, and
>(2) is it OK to use my alternative??
>
>Finally, as far as I can tell, there is a real race condition problem here 
>in a multiple-connection
>scenario (e.g. another task can cause the sequence to be incremented between 
>the insert
>and the select) - but wrapping a transaction around the insert and select 
>should
>take care of it... Thoughts??
>
>Thanks,
>Mark Dzmura
>
>