Using PostgreSQL hstore with Rails 4

Rails 4 has native support for PostgreSQL hstore.

Sadly, the tutorials and documentation I could find online, only point to how to use them with Rails 3, and only mention there will be “native” support with Rails 4.

Luckily, using hstore in Rails 4 is as easy as it should be. Native support means native: nothing needs to be done.

While previously you would need something like:

serialize :properties, ActiveRecord::Coders::Hstore

within your ActiveRecord subclass, now you just need to create the field with the appropriate migration

class AddPropertiesToProduct < ActiveRecord::Migration
  def change
    add_column :products, :properties, :hstore
  end
end

With this, the Product class will automatically serialize properties as to an hstore and present it to you as a Ruby Hash.

Two additional tips:

1. If you want the default value to be an empty hash, in the migration you need to specify it as {}.
2. I recommend using this gist or something similar, to enable the hstore extension when doing a rake db:schema:load. Usually, you enable hstore in a migration, but during development it’s very common to drop and recreate the database. Since hstore is now part of your schema, it will fail when you run rake db:schema:load as the migration hasn’t run yet and hstore is not enabled. This gist will fix that.