(ITS#6696) back-sql and pagedResultsControl can be extremely heavy due to no LIMIT

[Andrew.Gray@unlv.edu]

Full_Name: Andrew Gray
Version: 2.4.17
OS: Debian 5.0
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (131.216.14.1)


On receiving LDAP queries with a pagedResultsControl (in this case with a size
of 250), back-sql generates an extremely inefficient query for every iteration
in the form of:

SELECT DISTINCT ldap_entries.id,people.local_id,text('UNLVexpperson') AS
objectClass,ldap_entries.dn AS dn FROM ldap_entries,people,ldap_entry_objclasses
WHERE people.local_
id=ldap_entries.keyval AND ldap_entries.oc_map_id=1 AND upper(ldap_entries.dn)
LIKE upper('%'||'%OU=PEOPLE,DC=UNLV,DC=EDU') AND ldap_entries.id>250 AND (2=2 OR
(ldap_entries.id=ldap_entry_objclasses.entry_id AND ldap_entry_objclasses.oc_
name='UNLVexpperson'))

(this repeats for id>250, id>500, id>750, etc. etc.)

Ideally (IMO) there really should be a SQL LIMIT applied here, as in this case
slapd gets back a few tens of thousands of rows on every iteration, and the
memory usage explodes and eventually gets killed.