Unindexed Search question

[capareci at uol.com.br (Renato Ribeiro da Silva)]

I'm trying to understand why the search below is not indexed.

[27/Mar/2007:06:54:21 -0300] conn=341590 op=2 SRCH base="dc=domain,dc=com" scope=2 filter="(objectClass=posixAccount)" attrs="uid userPassword uidNumber gidNumber cn homeDirectory loginShell gecos description objectClass"

[27/Mar/2007:06:54:26 -0300] conn=341590 op=2 RESULT err=0 tag=101 nentries=8975 etime=5 notes=U

I look for the configuration of the indexes in the database and the objectclass attribute has system(read-only) index of Equality.
Any idea?

Thanks in advance,
Renato.