[development] One-to-one tables considered harmful

[Earl Miles]

David Strauss wrote:
> == What's bad about the current approach ==
> 
> The arguments for splitting table into one-to-one relationships are:
> 
> * Improving performance on systems that can only use table-level locking
> * Minimizing invalidations of the query cache

You *completely* missed the real argument:

Drupal is modular. Modules tend to have their own tables. Often these are 1::1 
tables.

I fail to understand how it is MySQL is unable to optimize for the 1::1 join 
case, especially when that 1::1 join is on the primary key. What am I missing 
that makes this join worse than other basic joins?