How to do case-insensitive order in Rails with postgresql

问题

I am in the process of switching my development environment from sqlite3 to postgresql 8.4 and have one last hurdle.

In my original I had the following line in a helper method;

result = Users.find(:all, :order => "name collate NOCASE")

which provided a very nice case-insensitive search. I can't replicate this for postgresql. Should be easy - any ideas?

Thanks.

回答1:

result = Users.find(:all, :order => "LOWER(name)")

To take a little bit from both Brad and Frank.

回答2:

LanecH's answer adapted for Rails 3+ (including Rails 4 and 5):

users = User.order('LOWER(name)')

Or create a named scope you can reuse:

class User < ActiveRecord::Base
  scope :order_by_name, -> { order('LOWER(name)') }
end

users = User.order_by_name

回答3:

Now with Rails 5.2 you probably will get a warning if using the accepted answer.

DEPRECATION WARNING: Dangerous query method (method whose arguments are used as raw SQL) called with non-attribute argument(s): "LOWER(?) ASC".

An alternative could be relying on Arel (it's merged now into Rails):

results = User.order(User.arel_table['name'].lower.asc)
# results.to_sql == "SELECT \"users\".* FROM \"users\" ORDER BY LOWER(\"users\".\"name\") ASC" 

回答4:

Have you considered storing your column as citext type? It really just internalizes the call to lower() as I understand it. It would be automatic for you afterwards. If there are times you need a case sensitive search, this may not be the best idea though.

回答5:

IN SQL you could use ORDER BY LOWER(columnname), no idea how to do it in Ruby. A functional index (also on LOWER(columnname) ) will help to speed things up.

来源：https://stackoverflow.com/questions/2983687/how-to-do-case-insensitive-order-in-rails-with-postgresql