Re: [PDO] Re: [PHP-DEV] [PATCH] New PDO methods for PostgreSQL driver

Lester Caine schrieb:
> Christopher Jones wrote:
>> Also
>> I haven't seen anything to explain your earlier comment to Lester that
>> "In particular you'll need two database connections (one with the
>> original driver and one with PDO) in order to use the native copy*
>> functions.".
>
> I see my name, but not connection with the quote ...
>
> But in addition to Denis's examples of where you need two database 
> connections,
> 2 phase commit across multiple databases has been part of Firebird for 
> many years, and other databases are now copying it. This requires 
> combining database connections in the one transaction, and is 
> something that PDO is unable to handle at all? It's one of the items 
> on http://wiki.php.net/internals/pdo/brainstorming?s[]=pdo ... as is 
> the question "Is the goal to eventually replace the native extensions?"
>
I see several possible ways without a complete new userland API to 
handle several database connections in PDO:

A basic driver specific dsn to handle several databases. Then you only 
need a driver specific handle switch function.
beginTransaction would default to all databases in your DSN.

PDO::firebirdUseDatabase();

+ Keeps the whole logic in the driver, can use optimized ways to handle 
transactions.
- Driver specific, the dsn gets very long.
- Removes the concept of PDO being a database instance.

A firebird specific pool driver could be used as well:

$dbh1 = new PDO(..);
$dbh2 = new PDO(..);

$dbhpool = new PDO('firebird:pool');

$dbhpool->firebirdAttachChild($dbh1);
$dbhpool->firebirdAttachChild($dbh2);
$dbhpool->beginTransaction()

+ Separates the basic usage from the advance usage, for most people PDO 
still will be one database handle.

The other route would be a dummy driver for all drivers:
Could be a bit problematical if you mix database drivers.

$dbhpool = new PDO('pool:');
$dbhpool->poolAttach($dbh1);
$dbhpool->poolAttach($dbh2);

$dbhpool->beginTransaction();

+ With some emulation it may work across Servers and Drivers via 
transaction save points?
+ Allows one instance to have less good transaction support in the pool, 
will get commit first, then the others...
- Not easy to handle, needs several hacks to hijack beginTransaction/commit
- Against the low level design of PDO

Or the same as transaction object...

$tobj = new PDOCrossTransaction();
$tobj->attach($dbh1);
$tobj->attach($dbh2);
$tobj->beginTransaction($options);

+ Can change the function declaration for transaction options

So I don't think there is a really a need to change fundamental all 
stuff of PDO to support this...

Oskar Eisemuth