Rails, ActiveRecord, query id in array of ints, keep order of passed array

Question

I am thinking about the best solution for a problem. Let's say that we have a list of ids of ActiveRecord model:

ids = [1, 100, 5, 30, 4, 2, 88, 44]

Then I would like to make query that selects all users for example with ids from the list but to keep the order. If I do

User.where(id: ids)

the response will be a list of users with asc order by id, but I want the order to be the same as in the array.

What do you think that it's the best solution here? Select all users and then to manipulate the list of ActiveRecord objects? Maybe there is a more clever way to do that.

Thanks!

Answer 1

With reference to here, for postgresql,

User.where(id: ids).order("position(id::text in '#{ids.join(',')}')")

Answer 2

regard less of MySQL and Postgresql, if you have a small size of ids,

User.where(id: ids).sort_by { |u| ids.index(u.id) }

Answer 3

If you are using MySQL, you can use FIELD to order results:

class User < ActiveRecord::Base
  def self.find_in_order(ids)
    self.where(id: ids).order("FIELD(id, #{ids.join(',')})")
  end
end

User.find_in_order([1, 100, 5, 30, 4, 2, 88, 44])

Answer 4

If you are using Postgres you can use intarray

class User < ActiveRecord::Base
  def self.find_in_order(ids)
    self.where(id: ids).order("idx(array[#{ids.join(',')}], id)")
  end
end

you should init module first

CREATE EXTENSION intarray

Answer 5

Another possibility for Postgres (9.4 or later):

ordered_ids = [1, 100, 5, 30, 4, 2, 88, 44]
User.joins("join unnest('{#{ordered_ids.join(',')}}'::int[]) WITH " \
           "ORDINALITY t(id, ord) USING (id)").reorder('t.ord')

Notice that the reorder is extremely important.

Solution based on https://stackoverflow.com/a/35456954