My simple python program dumps 1653992 items in 1654000 categories in :
real 3m12.029s
user 1m36.720s
sys 0m2.220s
It was running on the same machine as postgresql (AthlonXP 2500).
I Ctrl-C'd it before it dumped all the database but you get an idea.
If you don't know Python and Generators, have a look !