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Improved groups/groupings design in Moodle 1.9

The groups related database structure in 1.9 was reverted to 1.7, groupings are now implemented in a different way than in 1.8. The current design is compatible with 1.7 style groups.

Alternative rejected proposals

Changed groups/groupings relationship

In 1.8 both groups and groupings are not linked strictly to one course, you could use one group in several courses and groupings at the same time. This loose relationship of groups and groupings adds too much complexity and could be/is a source of bugs in code.

Solution: Each group and grouping links the course id directly. Groupings are only limiting the number of usable groups in activities. This allows free sharing of groups in groupings inside course without potential problems. This idea was proposed by Enrique. See attached db schema.



  • groupingid - default grouping used in course (new activities, etc.)


  • groupingid - grouping used in activity


renamed table


reverted to pre 1.8 state (with the password exception)


  • fewer tables
  • normalized
  • simpler SQL
  • easier backup/restore implementation
  • fully compatible with old group implementation in 1.7

Global groups

Global groups are not implemented in 1.9. They are not going to be implemented at the database level. Instead some other solution should be present in 2.0. This will require patching of enrolment framework and group/lib.php.

Groups API

Main public API is in lib/grouplib.php, modules should use only these functions.

Moodle core may use other functions defined in group/lib.php

See also

New feature ideas

Student self selection of group from grouping

To be implemented as normal module.

Linked groups

It would allow synchronizing of group membership from different courses; the idea is to have linkid in groups table and synchronize the groups membership in group functions for adding/removing of members for groups with the same linkid.

Group/grouping cloning

Cloning or duplicating is UI feature only, it helps to prefill new groups/groupings with existing data. In theory it could also copy existing grouping setups from other courses too.