class User < ActiveRecord::Base
  ransack_alias :ec, :email_cont
end

= search_form_for @q, url: users_path, html: {method: :get} do |f|
  = f.label :ec
  = f.search_field :ec
  = f.submit 'Search'

>> User.count
10

>> User.ransack({email_cont: "test@email.com"}).result.count
(93.8ms)  SELECT COUNT(*) FROM "users" WHERE ("users"."email" ILIKE '%test@email.com%')
1

>> params[:q]
{"ec" => "test@email.com"}

>> User.ransack(params[:q]).result.count
(28.4ms)  SELECT COUNT(*) FROM "users"
10

>> User._ransack_aliases
{"ec" => "email_cont"}