ActiveRecord: Filtering duplicates - ruby-on-rails

Question

Given this table:
Users
| id | name | active |
| 1 | bob | true |
| 2 | bob | false |
| 3 | alice | false |
How can i query this table using ActiveRecord (Rails 4.2, PostgreSQL), if the resulting relation should
have all attributes populated
not contain duplicate names
prefer active records in favor to inactive ones
be capable of calling .count, where count returns an integer
remain an ActiveRecord::Relation
The correct result set should look like this:
Users
| id | name | active |
| 1 | bob | true |
| 3 | alice | false |
What i tried so far:
# Works as for the result set, but raises when calling .count
User.select('DISTINCT ON (users.name) *')
.order(users.name, users.active DESC')

Answer 1

This should work
User.select('DISTINCT name').order('name, active DESC').count

Answer 2

Maybe
User.where.not(name: nil).where.not(active: nil)
This returns all users with a populated name and active boolean (ids will always be populated)
Then on that we call
.uniq_by(:name)
This gives us only records with a unique name
And finally
.sort_by { |a| a.active ? 1 : 0 }
Puts records with active: true at the start. So the method is:
User.where.not(name: nil).where.not(active: nil).uniq_by(:name).sort_by { |a| a.active ? 1 : 0 }
On this query we can call count to get the number of objects.
EDIT:
To keep as AR change uniq_by to uniq:
User.where.not(name: nil).where.not(active: nil).uniq(name).sort_by { |a| a.active ? 1 : 0 }

Answer 3

Since you're using PostgreSQL, you can use DISTINCT ON. Here's the SQL:
select distinct on (name) * from users order by name, active desc
And in Active Record:
>> User.order(name: :desc, active: :desc).select("distinct on (name) *")
User Load (2.5ms) SELECT distinct on (name) * FROM "users" ORDER BY "users"."name" DESC, "users"."active" DESC LIMIT $1 [["LIMIT", 11]]
=> #<ActiveRecord::Relation [#<User id: 2, name: "bob", active: true, created_at: "2017-09-15 03:58:23", updated_at: "2017-09-15 03:58:23">, #<User id: 3, name: "alice", active: false, created_at: "2017-09-15 03:58:35", updated_at: "2017-09-15 03:58:35">]>