Re: Indexing, use of slapindex

[Buchan Milne <bgmilne@staff.telkomsa.net>]

On Friday, 19 August 2011 11:27:03 anax wrote:
> Hi listers
> 
> Installation here:
> openldap-servers-2.4.15-7.fc11.i586
> 
> One master server, two backup servers (syncrepl).
> 
> All authentication and mailing is managed by ldap.
> 
> 
> 1. About indexing:
> 
> When i check the slapd-log, i see many
> 
> <= bdb_equality_candidates: (uidNumber) not indexed
> 
> <= bdb_equality_candidates: (gidNumber) not indexed
> 
> In the discussion about slapd tuning
> http://www.openldap.org/doc/admin24/tuning.html#Indexes, however, i read
> that if each entry in a certain set of ldap-entries has got the
> candidate-attribute, it is not worth while to index the attribute,
> because slapd needs to read each entry in any case in order to find the
> requested one.

This discussion you quote is about 'presence' indexing.

> this is the case for uidNumber as well as gidNumber,
> because both are compulsory attributes for objectClass posixAccount.
> 
> My first question:
> is it therefore correct to disregard the above indexing requests of slapd?

It is useful to do 'eq' indexing of uidNumber and gidNumber, you shouldn't 
quote stuff out of context (and also try and understand it ...).

> 2. About slapindex:
> 
> When it comes to use slapindex, the docu is not clear about how to do
> that. Some places say, that you need to stop slapd entirely,

In the case of using a static (slapd.conf) configuration.

> some places
> say that it is sufficient to put slapd in read-only mode for the
> corresponding background database,

This has never been an option. You could have provided a reference to the 
documentation in question.

> which in this case would be
> /etc/openldap/slapd.d/cn=config/olcDatabase\=\{2\}bdb.ldif
> this file contains both the olcReadOnly and the olcDbIndex attributes.

You should never actually consider these as files, they aren't for editing 
with an editor, this is only the backend store of the cn=config database. You 
should modify these values just like you modify entries in other databases - 
over the LDAP protocol.

> 
> So i could just add the following two lines in the above file:
> olcDbIndex: uidNumber eq
> olcDbIndex: gidNumber eq
> set the olcReadOnly attribute to TRUE, and restart slapd, and everything
> would be done automatically?

No, in back-config/cn=config configuration, it is sufficient to add the 
olcDBIndex values with e.g. ldapmodify.

Why is it sufficient?  If you do it over the wire, slapd can see what has 
changed, and can start creating a new index for you.

> Or would i need to invoke slapindex additionally with the following command
> slapindex -c

This is only applicable/necessary if using slapd.conf.

> Would the new indexes be propagated to the backup servers by syncrepl
> automatically?

No.

> If not, what would i have to change on the backup servers?

You should apply the applicable configuration change.

Regards,
Buchan