Case-insensitive find_or_create_by_whatever

I want to be able to do Artist.case_insensitive_find_or_create_by_name(artist_name)[1] (and have it work on both sqlite and postgreSQL)

What's the best way to accomplish this? Right now I'm just adding a method directly to the Artist class (kind of ugly, especially if I want this functionality in another class, but whatever):

  def self.case_insensitive_find_or_create_by_name(name)
    first(:conditions => ['UPPER(name) = UPPER(?)', name]) || create(:name => name)
  end

[1]: Well, ideally it would be Artist.find_or_create_by_name(artist_name, :case_sensitive => false)开发者_如何学Python, but this seems much harder to implement

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Rails 4 gives you a way to accomplish the same thing:

Artist.where('lower(name) = ?', name.downcase).first_or_create(:name=>name)

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This answer is for the additional questions asked in the question comments.

You wont be able to call the default find_or_create_by_name if you override that method. But you can implement your own as shown below:

def self.find_or_create_by_name(*args)
  options = args.extract_options!
  options[:name] = args[0] if args[0].is_a?(String)
  case_sensitive = options.delete(:case_sensitive)
  conditions = case_sensitive ? ['name = ?', options[:name]] : 
                                ['UPPER(name) = ?', options[:name].upcase] 
  first(:conditions => conditions) || create(options)
end

Now you can call the overridden method as follows:

User.find_or_create_by_name("jack")
User.find_or_create_by_name("jack", :case_sensitive => true)
User.find_or_create_by_name("jack", :city=> "XXX", :zip => "1234")
User.find_or_create_by_name("jack", :zip => "1234", :case_sensitive => true)

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You have to create an index based on the database.

postgreSQL

Create a lower case index on artist_name column.

CREATE INDEX lower_artists_name ON artists(lower(artist_name))

mySQL

Searches are case insensitive

sqlLite

Create a index on artist_name column with collate parameter

CREATE INDEX lower_artists_name ON artists( artist_name collate nocase)

Now you can use find_or_create in a DB independent manner:

find_or_create_by_artist_name(lower(artist_name))

Reference

PostgreSQL: Case insensitive search

sqlLite: Case insensitive search

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Talked about this one here. No one was able to come up with a solution better than yours :)