long time search for non-existent attributs (ITS#2506)

[extern.hendrik.harms@volkswagen.de]

Full_Name: Hendrik Harms
Version: 2.1.19
OS: solaris 5.8
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (194.114.62.38)


when I'm seaching for an non-existent attribute the ldap runs in heavy load
and the search will take a long time (> 5 minutes).
This could happend if there is a small bug in the search statement:

correct:   (&(objectclass=vwperson)(vwuid=123456))
incorrect: (&(objectclass=vwperson)(vwuuid=123456))
The attribute "vwuuid" does not exist.

With the incorrect statement I got the log:
 .... filter="(&(objectclass=vwperson)(?=undefined))"

I detected the problem on openldap-2.1.17. 
Then I upgrade my system to openldap-2.1.19 with berkeley-db 4.1.25
cause I thought ITS#2449 would fix my problem but it didn't :-(

My old openldap-2.0.25 didn't increase the cpu load.
There I found in the logfile:
 ... filter="(&(objectclass=vwperson)(badfilter))"

objectclass is indexed (eq)