Re: [PDO] Shared behavior of persistent connections

Hi Christoph,

I try to stay away as much as possible from persistent connections as 
they can cause more issues than what they actually solve. I think I even 
never used them on PDO.

That said, yes that's the behaviour I would expect. Transactions should 
be rolled back and the environment should be completely clean from 
anything that's suppose to last for the current session only.


Cheers

On 02/09/2016 14:18, Christoph M. Becker wrote:
> Hi!
>
> I wonder whether the shared behavior of persistent PDO connections is
> really desired, as it is implemented now.
>
> I stumbled upon this issue when I tried to resolve bug #63343[1] with PR
> #2112[2].  Nikita pointed out the actual problem, namely that destroying
> a PDO object will rollback the transaction on the inner object[3].
> Digging a bit deeper brought up the issue that not only a transaction
> would be rolled back, but also that the persistent_shutdown() method
> will be called in that case.  Consider the following script:
>
>     <?php
>     function foo() {return 1;}
>
>     $db1 = new PDO('sqlite::memory:', '', '',
>                    array(PDO::ATTR_PERSISTENT => true));
>     $db1->sqliteCreateFunction('foo', 'foo', 0);
>
>     $st1 = $db1->query('select foo()');
>     echo $st1->fetchColumn();
>
>     //$db1 = $st1 = null;
>
>     $db2 = new PDO('sqlite::memory:', '', '',
>                    array(PDO::ATTR_PERSISTENT => true));
>
>     $st2 = $db2->query('select foo()');
>     echo $st2->fetchColumn();
>
> The output is `11`.  However, uncommenting the line which will force the
> destruction of $db1, will also unregister the `foo` function, so the
> second ::query() will fail.  This can be quite confusing in a more
> complex script.
>
> Furthermore, in php_pdo_driver.h `pdo_dbh_request_shutdown` is
> documented as[4]:
>
> | called at request end for each persistent dbh; this gives the driver
> | the opportunity to safely release resources that only have per-request
> | scope
>
> However, `pdo_dbh_request_shutdown` isn't just necessarily called only
> at the end of the request, as shown above.
>
> Anyhow, if the shared behavior of persistent connections works as
> intented, the documentation should be updated respectively (and bug
> #63343 closed as being not a bug).
>
> [1] <https://bugs.php.net/bug.php?id=63343>
> [2] <https://github.com/php/php-src/pull/2112>
> [3] <https://github.com/php/php-src/pull/2112#discussion_r77312340>
> [4]
> <https://github.com/php/php-src/blob/PHP-7.0.11/ext/pdo/php_pdo_driver.h#L279-L282>
>


-- 
Matteo Beccati

Development & Consulting - http://www.beccati.com/