Simple MySQL "LIKE"-based infix search in Rails. Case and accent insensitive.

infix_search_named_scope.rb

class Foo < ActiveRecord::Base

  named_scope :infix_search, lambda { |string|
    if string.blank?
      {}
    else
      tokens = string.chars.downcase.split.uniq.first(10)  # Avoid too heavy queries.
      fields = %w[
        foo.bar foo.baz
        oink.boink
      ]
      like_query = %{ LOWER(CONCAT_WS(' ', #{fields.join(', ')})) COLLATE utf8_general_ci LIKE ? }
    
      templates = Array.new(tokens.length) { like_query }.join(' AND ')
      values = tokens.map {|token| "%#{token}%" }

      { :include => :oink, :conditions => [templates, *values] }
    end
  }

end