From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200309082241.h88Mf0o10340@candle.pha.pa.us>
Subject: Re: undefine currval()
In-Reply-To: <20030908211254.80421.qmail@web13801.mail.yahoo.com>
To: cgg007@yahoo.com
Date: Mon, 8 Sep 2003 18:41:00 -0400 (EDT)
Cc: pgsql-sql@postgresql.org
MIME-Version: 1.0
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Chris Gamache wrote:
> I'm using sequences and currval() to retrieve the last inserted row in a table.
> 
> 
> If currval() is undefined, as it is when a connection is made, then I know no
> rows were inserted in that table and can take a different action. This is
> problematic when using a connection pooling library, as the value of currval()
> for any given sequence could possibly be set from a previous "connection".
> 
> One (theoretical) workaround would be to issue some sort of command to the
> back-end database to wipe all values of currval() when a "new" connection is
> made. I've done some digging in the system tables and source code, and can't
> find an obvious solution. Perhaps one you you gurus can suggest a SQL statement
> to do such a thing. 
> 
> Alternately, if there is a better way to retrieve the last inserted row for any
> given table, I'd be very grateful for the tip. It would need to be independent
> of the connection history, and undefined if there has not been a row inserted
> to the table during a definable interval of time (drop anchor when the
> "connection" begins, raise anchor when the "connection" ends), and be
> independant of the other connections inserting rows to the same table.

I don't know how you could have an application that doesn't know if it
has issued a nextval() in the current connection. Unless you can explain
that, we have no intention of playing tricks with currval() for
connection pooling.

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