Mike,
> I'm curious what kind of performance differences there would be over
> using something like the nested-set model?
>
> Would this be faster, or slower?
The answer is "yes". ;-)
Which tree structures you use depends on what you're trying to accomplish and
what your use case is. There are some structures (for example, heirarchical
org charts) for which nested sets can't be beat. There are plenty of
reasons to implement other tree structures, such as graphs, cycles, and
delimited lists depending on what you're trying to depict.
What WITH is going to "replace", if anything, is the simple adjacency list
structure.
--
Josh Berkus
Aglio Database Solutions
San Francisco