ruby on rails - Public activity select unique foreign keys by created time -

i'm looking query activity object in app. i'm using public_activity gem , have list of activities connected several models , list out recent unique activity.

basically query recent activity particular tracking. let's i'm tracking button , it's id 29. want query out recent (one) instance of tracking id=29 , other tracking ids. don't know querying rails well. right line have displays activity:

@activities = publicactivity::activity.order("created_at desc").where(owner_id: current_user.id) 

let's have table of activities follows:

id  activity_id description created_on 1   3                  yesterday 2   3           unlike      2 days ago 3   6           comment     yesterday 4   7           review      yesterday 5   7           review      2 days ago 

i want pull out recent entries of each activity id @activities variable following:

id  activity_id description created_on 1   3                  yesterday 3   6           comment     yesterday 4   7           review      yesterday 

does public_activity have workaround this?

you can use combination of group , select accomplish this.

publicactivity::activity.   select("max(created_at) when, trackable_type").   group("trackable_type").   where(owner_id: current_user.id) 

here's output

+-------------------------+-------------------------+ | trackable_type          | when                    | +-------------------------+-------------------------+ | report                  | 2015-11-27 20:25:31 utc | | quickanswer             | 2016-01-04 23:36:21 utc | | comment                 | 2015-10-23 15:35:32 utc | | takenexam               | 2016-01-04 23:46:11 utc | | seenvideo               | 2015-08-23 21:27:58 utc | | provider                | 2015-09-17 23:47:40 utc | | answerforrecommendation | 2015-08-18 15:13:03 utc | | subscription            | 2015-08-24 08:37:08 utc | +-------------------------+-------------------------+