CODEWITHSUNDEEP
ruby-on-railsrubyactiverecordruby-on-rails-5
matQ
matQ

Reputation: 617

Efficent way to select belongs_to model from another Model, in Rails 5?

I have 2 models: 

Contact -> has_many :messages

and 

Message -> belongs_to :contact

I want to select the last 10 contacts (as array of object, not only ids) from my messages table

this is my attempt (and it works fine):

Contact.where(id: Message.pluck(:contact_id).uniq.last(10))

BUt is there another better or rails way to do this?

EDIT I want to select the last 10 contacts from my messages table

Upvotes: 0

Views: 506

Answers (2)

spickermann
spickermann

Reputation: 106802

I would do this in one database query.

Contact
  .distinct
  .joins(:messages)
  .order('messages.created_at DESC')
  .limit(10)

Upvotes: 3

Anuj Khandelwal
Anuj Khandelwal

Reputation: 1244

You could try the following query:

Contact.where(id: Message.distinct.order(created_at: :desc).limit(10).select(:id))

This would produce the following SQL:

"SELECT  DISTINCT \"messages\".\"id\" FROM \"messages\"   ORDER BY \"messages\".\"created_at\" DESC LIMIT 10"

Upvotes: 0

Related Questions