Filtering on meberUid vs cn

["Marantz, Roy" <Roy.Marantz@deshaw.com>]

Please excuse me if this is an off list topic.  I think this may be
specific to OpenLDAP
so I'm trying here.

I'm running OpenLDAP 2.4.7 w/ BerkeleyDB 4.6.21 on Solaris-10.

I'm running OpenLDAP as a fairly standard NIS replacement.  In
particular I have a DIT
ou=group,dc=nyc,dc=deshaw,dc=com made of objects of class posixGroup
(from the
supplied nis.schema file).  Solaris want to get a getgrmember()
(undocumented subroutine
call) which does a ldap search like the first one following.

This search returns nentries=0
ldapsearch -x -LLL -h 127.0.0.1 -b 'ou=group,dc=nyc,dc=deshaw,dc=com'
'(&(objectClass=posixGroup)(memberUid=marantz))'

conn=2354 op=1 SRCH base="ou=group,dc=nyc,dc=deshaw,dc=com" scope=2
deref=0 filter="(&(objectClass=posixGroup)(memberUid=marantz))"
conn=2354 op=1 SEARCH RESULT tag=101 err=0 nentries=0 text=

But this search shows at least one object that I think should match
ldapsearch -x -LLL -h 127.0.0.1 -b 'ou=group,dc=nyc,dc=deshaw,dc=com'
'(&(objectClass=posixGroup)(cn=www))'
dn: cn=www,ou=Group,dc=nyc,dc=deshaw,dc=com
objectClass: posixGroup
objectClass: top
cn: www
userPassword:: XXXXXXXXXXXX
gidNumber: XXXX
memberUid: XXXXXX
memberUid: marantz
memberUid: XXXXXX
memberUid: XXXX
memberUid: XXXXXX
memberUid: XXXXXX
memberUid: XXX
memberUid: XXXXXXXX

conn=3087 op=1 SRCH base="ou=group,dc=nyc,dc=deshaw,dc=com" scope=2
deref=0 filter="(&(objectClass=posixGroup)(cn=www))"
conn=3087 op=1 SEARCH RESULT tag=101 err=0 nentries=1 text=

The only difference I can find is the Equality Matching value for the 2
attributes.  I
notice that cn has a Equality Matching value of caseIgnoreMatch vs.
caseExactA5Match for
memberUid. (at least according to
http://ldap.akbkhome.com/index.php/objectclass/posixGroup.html)
I don't see how, but could that be involved in my problem?

Any help would be greatly appreciated.
Thanks.
Roy