test data for query optimizer

I'd like to look at the performance of the query optimizer (both the
traditional one and GEQO) when joining large numbers of tables: 10-15,
or more. In order to do that (and to get meaningful results), I'll
need to work with some data that actually requires joins of that
magnitude. Ideally, I'd like the data to be somewhat realistic -- so
that the performance I'm seeing will reflect the performance a typical
user might see. (i.e. I don't want an artificial benchmark)

However, I don't possess any data of that nature, and I'm unsure
where I can find some (or how to generate some of my own). Does
anyone know of:
   - a freely available collection of data that requires queries   of this type, and is reasonably representative of
"realworld"   applications
 
   - or, a means to generate programatically some data that   fits the above criteria.

Thanks in advance,

Neil

-- 
Neil Conway <neilconway@rogers.com>
PGP Key ID: DB3C29FC