In Ruby/Rails how to rank objects by number of associations?

Question

In Rails 7:

I have an Object which has many Associations.

Associations have a :start_time datetime attribute.

I want to return Objects, ranked in order by number of Associations over a certain period of time.

I have tried:

creating an array of Associations from date1 to date2
using group_by and each with object to create a hash of Object.ids and frequencies

but I cannot figure out how to rank them by frequency.

I also think their is an easier way to do this.

I am sure this will get downvoted for lack of detail/code, but the question is very general and the use case common.

Any suggestion is appreciated.

Are they ActiveRecord models or just ruby objects? Meaning should the ordering happen in the database or in memory? — Siim Liiser, Aug 08 '23 at 08:01
They are both active record models with tables in the Postgres DB. — user2799827, Aug 08 '23 at 08:40
Would this help? https://stackoverflow.com/questions/1402682/how-to-sort-by-count-with-postgresql — Siim Liiser, Aug 08 '23 at 09:08
That is what I am trying to do. I am not sure how to translate the sql into an Active Record query. — user2799827, Aug 08 '23 at 09:19
Maybe this: https://stackoverflow.com/questions/40111685/order-by-count-of-a-models-association-with-a-particular-attribute — user2799827, Aug 08 '23 at 09:48

score 1 · Accepted Answer · answered Aug 08 '23 at 22:08

In case anyone else is looking.

Essentially I did something akin to the following:

in the Association model:

  def self.grouped
    exclusionId = Object.find_by(name: 'Excluded Object').id
    Association.joins(:object).where.not(object_id: exclusionId)                                                                                   .group_by{|assoc| assoc.object_id}
  end

  def self.ranked_objects
    association_by_object = Association.grouped.each_with_object({}) { |(k,v),h| h[k] = v.size }
    (association_by_object.sort_by{|key, value| value}).reverse
  end

Then in the applicable controller action:

  def objects_ranked
    render json: Association.ranked_objects.to_json
  end

In Ruby/Rails how to rank objects by number of associations?

1 Answers1