Rails group_by id and group created - ruby-on-rails

Question

I have a model call GcMission
it contains gamecharacter_id, mission_id and of course created_at.
Now I need to group_by gamecharacter_id, and then group the created_at to see how many mission_id per day.
I assum the result will be like
{
69 => {
'2017-08-18' => 1
},
75 => {
'2017-08-18' => 2
},
78 => {
'2017-08-18' => 1,
'2017-08-19' => 1,
}
}
But I am stuck at that.
Here is what I've written.
GcMission.select('gamecharacter_id, mission_id, created_at').where(mission_id: assign_mission_ids).where('finish_counter >= 1').group_by{|a| a.gamecharacter_id}
And the result is like
{
69 => [
[0] #<GcMission:0x007ff6c6a53650> {
:gamecharacter_id => 69,
:mission_id => 3,
:created_at => Tue, 18 Apr 2017 03:20:36 UTC +00:00
}
],
75 => [
[0] #<GcMission:0x007ff6c6a52d18> {
:gamecharacter_id => 75,
:mission_id => 3,
:created_at => Tue, 18 Apr 2017 06:38:27 UTC +00:00
},
[1] #<GcMission:0x007ff6c6a52408> {
:gamecharacter_id => 75,
:mission_id => 4,
:created_at => Tue, 18 Apr 2017 07:55:40 UTC +00:00
}
],
78 => [
[0] #<GcMission:0x007ff6c6a51be8> {
:gamecharacter_id => 78,
:mission_id => 3,
:created_at => Tue, 18 Apr 2017 17:29:24 UTC +00:00
},
[1] #<GcMission:0x007ff6c6a51580> {
:gamecharacter_id => 78,
:mission_id => 4,
:created_at => Wed, 19 Apr 2017 03:20:31 UTC +00:00
}
]
}

Answer 1

Try Following
gc_missions = GcMission.select("gamecharacter_id, DATE(created_at) AS date,
COUNT(mission_id) AS mission_count")
.group('gamecharacter_id, date')
If you want count of unique mission_id per gamecharacter_id per day use
COUNT(DISTINCT(mission_id))
You may like to verify using following code
gc_missions.each {|gc| puts "#{gc.gamecharacter_id}, #{gc.date}, #{gc.mission_count}"}