Date: Wed, 7 Feb 2001 20:56:12 +0100
From: "Thies C. Arntzen" <thies@thieso.net>
To: Bruce Momjian <pgman@candle.pha.pa.us>
Cc: "Thies C. Arntzen" <thies@digicol.de>, Rasmus@candle.pha.pa.us,
	Lerdorf <rasmus@php.net>,
	PostgreSQL-interfaces <pgsql-interfaces@postgresql.org>,
	php-dev@lists.php.net
Subject: Re: PostgreSQL and PHP persistent connections
Message-ID: <20010207205611.A11560@schnuffel.thieso.net>
References: <200102071912.OAA27530@candle.pha.pa.us>
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	from pgman@candle.pha.pa.us on Wed, Feb 07, 2001 at 02:12:26PM
	-0500

On Wed, Feb 07, 2001 at 02:12:26PM -0500, Bruce Momjian wrote:
> Thies, we talked at LinuxWorld about improving the reliability of
> persistent PostgreSQL connections in PHP.

    cc'ing php-dev

    bruce, 
    hope you had a successful show!

> 
> I believe the problem is that persistent connections sometime do not
> pass clean sessions because of open transactions and SET changes to the
> session.

    yep...

> 
> We discussed using 'ROLLBACK' before passing a connection to a new user,
> but the problem was that ROLLBACK with no open transaction causes a
> server log error message.  We discussed adding 'ROLLBACK SILENT' to fix
> this, but I believe a better, more portable solution is a simple "BEGIN
> WORK;ROLLBACK".  This will do nothing if there is no open transaction,
> and will ROLLBACK any open transaction.  I propose this be sent by PHP
> as the first query when passing persistent connections.

    i'll have a look at that tomorrow (if my family allows;-). if
    "BEGIN WORK;ROLLBACK" does not stack transactions i think you
    might have found the solution to the php-postgres problem! do
    you know how other script-interfaces (perl) to postgres
    handle the very same thing?

> 
> As far as SET changes, does anyone on the PostgreSQL interfaces list
> have a suggestion on how to RESET all session parameters?  Seems we may
> need to add this feature in to the backend.

    with the oracle driver (i wrote) there is a neat thing in the
    oci-libs: you have a server-handle _and_ a session handle.
    the session handle sits "on" the server-handle and keeps
    _all_ session specific data, the server handle "only" carries
    the pure connection to oracle. so i keep the server handle
    persistent and allocate/free session handles on it for each
    request to PHP. that way the sessions are always clean. but i
    also do a forces rollback on the session handle before i free
    it on request-end so that in case of a script error all
    outstanding transactions are rolled-back.

    regards,
    tc