• Migrating an existing horde installation's group from SQL to LDAP

++ Manually
I strongly suggest you don't play around in production!

+++ Basics

• Configure a separate vhost each for the db-based and the sql-based setup
• create conf-{sqlvhost}.host.com.php and conf-{ldapvhost}.host.com.php each containing only the php tag and all $conf['group'] stuff.
• use the docs on how to setup horde for ldap groups.
• ensure both are basically working (create some bogus group and add some user in each backend)
• Now open https://{host}/horde/admin/groups.php or https://{host}/admin/groups.php in each site.
• Create all the missing groups in the ldap backend. add all the missing users.

+++ Permissions
(assuming SQL backend) select * from horde_perms where perm_data like "%groups%";

Each permission assigned to a group by numeric group id must be cloned to be used by the ldap group backend.
Best use the group admin screen.

Do not attempt to edit the perms using an sql statement.

+++ Shares
(assuming sharesng sql backend is used)
Find any apps using sharesng shares
mysql> show tables like "%sharesng_groups%";

For each found table,

For each group_uid which is numeric, look up the group name
mysql> select group_name from horde_groups where group_uid=N;

Find the corresponding ldap group id, for example
GroupName,ou=hordegroups,dc=domain,dc=com

Create a corresponding entry with the same perms.

+++ Cache

Clear horde group cache and horde shares cache once you're done.

++ By script

TBD