CRM_ACL_BAO_ACL::whereClause should call hook aclGroups BEFORE it calls aclWhereClause.

Some calls to the alphabetical pager take literally hours for users with many (~50) ACLs. CRM_ACL_BAO_ACL::whereClause can be used to simplify the where clause, but you have to parse lots of raw SQL to do this.

Since sometimes a smaller set of ACLs is equivalent to the bigger set (say, if every contact in 49 of the ACLs is contained in a "master" ACL that covers all the other 49 groups), it would help to call CRM_Utils_Hook:aclGroup during the call to CRM_ACL_BAO_ACL::whereClause(), after the call has calculated $ids, but before it starts pumping out SQL.

Use case for this is in the forums: http://forum.civicrm.org/index.php/topic,14165.0.html

Attached file is a patch against v3.2.