I have 3 models,

• User (has_many :posts)
• Post (Belongs_to :user, has_many :categories through: :posts_categories)
• Category (has_many :posts through: :posts_categories)

Now, I want to find and order all users who have submitted most posts in a category, how do I achieve this using Ransack search

Eg. For category 'Fashion' I want to fetch & order users by number of user's posts in fashion.

Desired result should give,

• Mark (7 posts in fashion)
• Dave (5 posts in fashion)
• Carla (4 posts in fashion) .. so on

Note: Would prefer a solution that is compatible with postgres

My ransack search in controller

@search = User.all.search(params[:q])
@searchusers = @search.result(distinct: true)

@findusers = @searchusers.joins(posts: :categories)
            .where(categories: { id: params['q']['posts_categories_id_eq'] })
            .group('users.id')
            .order('count(posts.id) desc').page(params[:page]).per(12)

Note: This works perfectly well in SQLite but fails in PG with below error 'PG::Error: SELECT DISTINCT, ORDER BY expressions must appear in select list'