Rails, Mongoid and complex query

Question

User has_many items Item belongs_to Client

Using mongoid (i don't think it's mongoid specific, but anyway) i need to gather all clients by given user. Currently i use:

@clients = current_user.items.map{|c| c.client}

but for sure it's not good, and not acceptable. What is the best way for implementation?

That's not horrible or anything. But it's probably best if you describe via some pseudo code what you'd like your ultimate syntax to look like. Basically it sounds like you'd like to apply some syntactic sugar to your code, and have cleaner code, maybe something like: clients = user.all_clients — RadBrad
– RadBrad, Commented Aug 23, 2012 at 17:05
First of all, as result is have an array, and it's not very handy. Second, i'm not sure, but i think with huge amount of records it's not good to put it on ruby's shoulders? (again, it's mongodb) — There Are Four Lights
– There Are Four Lights, Commented Aug 23, 2012 at 17:17
Got it, I think you have a couple of options, either hand craft a SQL statement that does what you want, or use ActiveRecord includes (Eager loading). Deciding between the two is probably application specific. link Check out section on Eager Loading — RadBrad
– RadBrad, Commented Aug 23, 2012 at 18:19

Andrea Reginato · Accepted Answer · 2012-08-23 21:13:08Z

2

To not run into the N+1 problem I would do something like this.

# first you retrieve all client ids
ids = current_user.items.map(&:client_id)

# then you retrieve all clients at once
@clients = Client.in(id: ids)

answered Aug 23, 2012 at 21:13

Andrea Reginato

1,3381 gold badge17 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

1 Answer 1