Slow search for (cn=*<2-3 letters>*)

[Hallvard B Furuseth <h.b.furuseth@usit.uio.no>]

Searches like (cn=*foo*) and (cn=*yy*) are very slow.  They hit our
15-second timelimit.  Don't the use indexes?  If not, can they be
configured to use them?

(Searches for one-letter substrings return results rather slowly too,
but they hit the sizelimit first, so it doesn't really matter.)


Commands:
  ldapsearch -xLLL -h ldap.uio.no -b ou=people,dc=uio,dc=no "(cn=*foo*)"
  ldapsearch -xLLL -h ldap.uio.no -b ou=people,dc=uio,dc=no "(cn=*yy*)"

System:
  OpenLDAP 2.1.22 and 2.1.19 using LDBM backend with Berkeley DB 4.1.25,
  i686 Linux, 2G memory,
  265000 entries in the database,
  185000 entires under ou=people,dc=uio,dc=no (no subtrees under it).

slapd.conf:
  ...
  threads         32
  sizelimit       50
  idletimeout     180
  timelimit       15
  ...
  database        ldbm
  suffix          "dc=uio,dc=no"
  cachesize       50000
  dbcachesize     50000000
  directory       /ldap/usr/var/base-db
  index   default                 pres,eq
  index   objectClass             eq
  index   cn                      pres,eq,sub
  index   uid                     pres,eq,sub
  index   ou                      pres,eq,sub
  index   mail                    pres,eq,sub
  index   telephoneNumber         pres,eq,sub
  index   eduPersonOrgUnitDN      eq
  index   eduPersonPrincipalName  eq
  index   uidNumber               eq
  index   gidNumber               eq
  ...

-- 
Hallvard