slapd presence index option working?

[Trevor Porter <Trevor@PocketScience.com>]

I'm trying to create a presence index for one of the attributes in my
directory, however, it doesn't seem to have an effect on search performance.
I've had no problems using equality and substring indices. For example, if I
put the following in my slapd.conf file:
 
   index foo pres
 
I would expect to get fast search performance for the following search
query:
 
   ldapsearch "foo=*"
 
My database has around 86K entries and it appears to be searching the entire
directory for the above query. Any ideas?
 
...Trevor