How to get id after insert data

[eluser]Wayne Smallman[/eluser]
[quote author="darkhouse" date="1248037559"]Just adding my 2 cents. I once had an application (not code igniter, this is like 5 years ago) give me a terrible problem where I had 2 people register at the exact same time. I was returning mysql_insert_id() but it returned the same id to both of them.[/quote]This is the problem I'm working through right now, and is the reason I need to know more about how $this->db->insert_id() works.

I am surprised this problem hasn't yet been resolved by the database vendors. Surely a simple solution would be to serialize each transaction, to identify them for the purposes of post processing?