Re: PostgreSQL and PHP persistent connections

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