how to speed up filtering of dn's

Hi all,

I want to find all entries in my ldap directory that contain certain ou's, e.g.

ldapsearch -x "(ou:dn:=Administration)"

which returns (in my case) all entries that correspond to administrative staff. The query works but it is slow and puts a high load on the ldap server.

I wonder if I can create an index which would speed things up, but I could not figure out what I should index.

Note that I cannot do this using a specific basedn, because we have administrative staff in several subtrees of our ldap hierarchy.

Best