Re: preloading modules and apache::dbi

On 01/19/2012 08:48 AM, Josh Narins wrote:
> The idea of Apache::DBI is that you get to pool connections.
>
> If you call Apache::DBI->new and there is a spare connection, you get
> it, if not, one is created for you.

This isn't quite accurate. Apache::DBI doesn't do connection pooling, it 
manages persistent connections. It's still one connection per-process 
(per connection attributes) and connections aren't shared between child 
processes (that's where things get messy).

Apache::DBI makes sure you don't create more connections than needed and 
makes sure that the persistent connections are still connected before 
handing them back.

> You almost certainly don't want one $db object being shared as a member
> of a class, unless your entire program also happens to represent one DB
> transaction.

This is actually a pretty common and ok pattern. Remember that execution 
through a request is still linear (not threaded or handled by multiple 
processes) so if you want your whole request to be a single transaction 
you can, or if you want it to auto-commit you can, or if you want it to 
be a mix of transactions and auto-committed statements, you can do that too.

When you use Apache::DBI and then call DBI->connect or 
DBI->connect_cached you'll get the same database connection every time 
(per process of course).

-- 
Michael Peters
Plus Three, LP