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Re: PostgreSQL and PHP persistent connections

From: "Thies C(dot) Arntzen" <thies(at)thieso(dot)net>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: "Thies C(dot) Arntzen" <thies(at)digicol(dot)de>, Rasmus(at)candle(dot)pha(dot)pa(dot)us, Lerdorf <rasmus(at)php(dot)net>, PostgreSQL-interfaces <pgsql-interfaces(at)postgresql(dot)org>, php-dev(at)lists(dot)php(dot)net
Subject: Re: PostgreSQL and PHP persistent connections
Date: 2001-02-07 19:56:12
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-interfacespgsql-jdbc
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

    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.


> 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.


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