How do you normally sort items in Rails?

Question

I have a little example Rails app called tickets, which views and edits fictional tickets sold to various customers. In tickets_controller.rb, inside def index, I have this standard line, generated by scaffolding:

@tickets = Ticket.find(:all)

To sort the tickets by name, I have found two possible approaches. You can do it this way:

@tickets = Ticket.find(:all, :order => 'name')

... or this way:

@tickets = Ticket.find(:all).sort!{|t1,t2|t1.name <=> t2.name}

(Tip: Ruby documentation explains that sort! will modify the array that it is sorting, as opposed to sort alone, which returns the sorted array but leaves the original unchanged).

What strategy do you normally use? When might you use .sort! versus the :order => 'criteria' syntax?

Answer 1

Use :order => 'criteria' for anything simple that can be done by the database (ie. basic alphabetical or chronological order). Chances are it's a lot faster than letting your Ruby code do it, assuming you have the right indexes in place.

The only time I could think you should use the sort method is if you have a complex attribute that's calculated at run-time and not stored in the database, like a 'trustworthiness value' based off number of good/bad responses or something. In that case it's better to use the sort method, but be aware that this will screw things up if you have pagination in place (each page will have ITS results in order, but the set of pages as a whole will be out of order).

Answer 2

I specify an order in the ActiveRecord finder or in the model association because sorting using SQL is faster. You should take advantage of the features offered by the RDBMS when you're able to do so.