Posted by Gordon on 12/19/07 16:43

On Dec 19, 12:33 pm, Tim Hunt <tim.n.h...@gmail.com> wrote:
> On Dec 18, 5:31 pm, Gordon <gordon.mc...@ntlworld.com> wrote:
>
>
>
> > I am currently working on some code for my CMS that creates a site
> > folder, then creates all the necessary child folders inside it. The
> > method that creates folders needs to insert into 2 tables so it wraps
> > the operation in a transaction. (psuedocode below)
>
> > public function createItem ($parent)
> > {
> > $this -> database -> beginTransaction ();
> > $this -> database -> query ('INSERT INTO items (param1,
> > param2 ... ) values (val1, val2 ... )');
> > $newId = myMethodForGettingInsertId ();
> > $this -> database -> query ('INSERT INTO folders (id, param3 ... )
> > values ($newId, val3 ... )');
> > $this -> database -> commit ();
> > return ($newId);
>
> > }
>
> > (the real code is obviously a lot more sophisticated and has all the
> > error checking and rollbacks and what have you but the mock up code
> > below is clearer regarding the intent of the method)
>
> > In my site creating class I have something along the lines of
>
> > public function createItem ($parent)
> > {
> > $this -> database -> beginTransaction ();
> > $newId = parent::createItem ($parent);
> > parent::createItem ($newId, 'images');
> > parent::createItem ($newId, 'css');
> > parent::createItem ($newId, 'other_stuff');
> > $this -> database -> commit ();
>
> > }
>
> > This obviously causes an exception. I can take the transaction code
> > out of my folder class but the creation of a folder should be atomic.
> > I could leave it out of the site creation class, but I really do need
> > site creation to be atomic as well.
>
> > Is there a way of determining that I am inside a transaction before
> > attempting to start one?
>
> Only if you keep track of it yourself, write your own
> beginTransaction() and commit() methods and use a transaction count
> variable.
>
> All calls to your own beginTransaction() and commit() methods
> increment/decrement the transaction counter respectively. Only the
> first call to beginTransaction calls $this->database->beginTransaction
> and $this->database->commit() is only called when the transaction
> counter reaches 0 again.

Yes, that sounds like a cunning plan. I can add that into my PDO
wrapper easily enough I think. Thanks for the help.

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