Counting distinct or unique records

[wynksaiddestroy]

As an example use the three classes from the documentation: User, Group and Membership. Now assume that a user can have multiple memberships for a group.
Is there a way to save the distinct or unique user count for a group?

So I don't want this:

group.users.size

… but:

group.users.distinct.size

[wynksaiddestroy]

If I change the user model as follows:

class User < ActiveRecord::Base
  has_many :group_memberships
  has_many :groups, -> { distinct }, through: :group_memberships
end

… i won't have to use distinct anymore. But my counter on the membership model:

counter_culture :group, column_name: "members_count"

won't count the distinct users but all.

[magnusvk]

This isn't possible with counter_culture as far as I know. If you had a pull request that added support for this, I'd be happy to take a look at it though!