PostgreSQL + Rails citext

问题

I am trying to move to heroku which uses PostgreSQL 8.4 which has a citext column type which is nice since the app was written for MySQL.

Is there any way to use :citext with rails (so that if the migrations are run on MySQL the citext would just use string/text?

I found this ticket, but it seems like it isn't going to be a part of rails for a while: https://rails.lighthouseapp.com/projects/8994/tickets/3174-add-support-for-postgresql-citext-column-type

回答1:

Rails 4.2+

Rails 4.2 has native support for the citext column type.

Rails < 4.2

If you're using Rails < 4.2, you can try using the activerecord-postgresql-citext gem.

This allows you to write migrations like this:

def up
  enable_extension("citext")                   

  create_table :models, :force => true do |t|  
    t.citext :name                             
    t.timestamps                               
  end                                          
end

回答2:

Just for the record. Seems like rails 4.2 has native support for this.

Added support for the citext column type in the PostgreSQL adapter.

http://guides.rubyonrails.org/4_2_release_notes.html

回答3:

I'm pretty sure that Rails has only a limited vocabulary of data types. You will likely have to use good old-fashioned SQL to deal with any other types.

回答4:

As others have mentioned, Rails now has native support for the citext column type (since 4.2).

To migrate existing columns you need to enable the citext extension and then change_column. Change colum is non-reversible so you'll need separate up and down methods.

class ConvertUserNameToCaseInsensitive < ActiveRecord::Migration[6.0]
  def up
    enable_extension 'citext' # only the first migration you add a citext column
    change_column :user, :name, :citext
  end

  def down
    change_column :user, :name, :string
    disable_extension 'citext' # reverse order, only the first migration you add a citext column (this will be the last time you remove one in a rollback)
  end
end

Disable extension is only required the last time you remove a citext column when rolling back so rather than add ugly comments it might be better to have separate migrations and explain the reason why in your commit message:

# migration 1.rb
class EnableCitext < ActiveRecord::Migration[6.0]
  def change
    enable_extension 'citext'
  end
end


# migration 2.rb
class ConvertUserNameToCaseInsensitive < ActiveRecord::Migration[6.0]
  def up
    change_column :user, :name, :citext
  end

  def down
    change_column :user, :name, :string
  end
end

来源：https://stackoverflow.com/questions/2619998/postgresql-rails-citext