Search on whole tree gives result, search on subtree not

[Karsten Heymann <karsten.heymann@googlemail.com>]

Hi,

I've started playing around with slapd (2.4.23-7.2 from debian
squeeze) again and stumbled across a very strange phenomenon: When
searching the whole tree for an entry it is found immediately:

0|kheymann@ds1-01:~$ ldapsearch  -x -h localhost -b o=mycompany uid=aaa uid
# extended LDIF
#
# LDAPv3
# base <o=mycompany> with scope subtree
# filter: uid=aaa
# requesting: uid
#
# aaa, 2, customers, marketing, mycompany
dn: uid=aaa,contractID=2,ou=customers,ou=marketing,o=mycompany
uid: aaa
# search result
search: 2
result: 0 Success
# numResponses: 2
# numEntries: 1

But when searching any of the intermediate subtrees, no result is
returned after a short delay:

0|kheymann@ds1-01:~$ ldapsearch  -x -h localhost -b
ou=marketing,o=mycompany uid=aaa uid
# extended LDIF
#
# LDAPv3
# base <ou=tc,o=mycompany> with scope subtree
# filter: uid=aaa
# requesting: uid
#
# search result
search: 2
result: 0 Success
# numResponses: 1

The uid attribute is indexed with

0|root@ds1-01:/etc/ldap/slapd.d/cn=config# grep -e ' uid ' *ldif
olcDatabase={1}hdb.ldif:olcDbIndex: uid eq

and slapindex generated the index without any error messages. This
also seems to happen only with entries created while the slapd is
running while the entries from the initial import do not whoe this.

This seems very weird to me. Any hints what could cause this behaviour
and what could possibly fix it?

Thanks in advance,
Karsten