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To: "Bijl, Gomar" <gomar.bijl@bu400.nl>
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Date: Wed, 2 Jul 2008 19:43:42 +0200
References: <6873E3E399117E4BA9FD3854A3DB93814B67EC@NL67S011.cal-consult.nl>
Subject: Re: [PHP-DEV] [PATCH] ODBC_Pconnect should not Commit/Rollback database transactions of previous data
From: mls@pooteeweet.org (Lukas Kahwe Smith)


On 26.06.2008, at 10:46, Bijl, Gomar wrote:

> Hi
>
> We have a problem with the (ODBC) persistent database connection. We
> have found that every PHP-session, using the same dsn, user and
> password, are getting the same persistent connection by a reasonable
> chance.
> Also meaning that if a database transaction was not finished, other
> PHP-session can do a rollback or commit of that transaction.

Right, I presume you are aware of the documentation on this topic,  
which affects all rdbms extensions. Just to be sure here is the link:
http://php.net/manual/en/features.persistent-connections.php

> To overcome these problems one has to tag the connections. I suggest  
> to
> use a new parameter on ODBC_(p)connect: Tag, a string parameter. If  
> used
> it tries to re-connect to the connection with the same tag, if not
> existing it creates a new-connection.
> For example the tag parameter is filled with the session_ID() to  
> ensure
> that a connection is bounded to one PHP-session. But also an extension
> on this value is possible:  (Session_ID() + 'Log') or (Session_ID() +
> 'Data').
> And if somebody does not uses this tag parameter, it works in the old
> way, so these solution is downwards compatible.

Several extensions offer a "new_link" optional boolean parameter to  
ensure that a new connection is returned if there is already an  
existing connection in this request:
http://php.net/mysql_connect

IIRC this "feature" (returning an existing connection link of a  
section connection is made to the same server in the same request) is  
not present in all extensions, but since ext/mysql was sort of a  
template for many extensions, I think a lot of developers copied this  
behavior. Note that this parameter is not available in the pconnect  
alternatives.

ideally the odbc extension should do a "change user", which would  
clean up all the session specific stuff inside the connection (next to  
open transactions, there are other stuff like date formats etc that  
could also be set). i am not however sure if this feature exists in  
all rdbms. afaik the mysql developers are looking to implement this  
into mysqlnd.

either way, any solution should try to be consistent across all  
affected extensions.

regards,
Lukas Kahwe Smith
mls@pooteeweet.org