Rails Postgresql array of hstore

In principle, yes, but as you've found it isn't being escaped correctly when saved. I've just today logged an issue about that, see https://github.com/rails/rails/issues/11135 (includes a fix patch and some demo code)

This is a bug that exists at least in Rails 4.0.1 .

A pull request was proposed to fix it, but until it is merged you can monkey-patch Rails:

# config/initializers/extensions/postgres.rb
module ActiveRecord
  module ConnectionAdapters
    class PostgreSQLColumn < Column
      module Cast
        private

          def quote_and_escape(value)
            case value
            when "NULL"
              value
            else
              "\"#{value.gsub(/(["\\])/, '\\\\\1')}\""
            end
          end
      end
    end
  end
end

Sidenote, I had trouble testing this in the Rails console because the initializer wasn't getting loaded there. You can do so with:

load "#{Rails.root}/config/initializers/extensions/postgres.rb"

You can sue the activerecord-postgres-hstore gem:

https://github.com/engageis/activerecord-postgres-hstore

From the docs:

1. Create a hstore-backed field:

   class Person < ActiveRecord::Base serialize :data, ActiveRecord::Coders::Hstore end

2. Add fields to to it:

   person = Person.new person.data['foo'] = 'bar' person.save

3. Query it:

   Perosn.where("data -> 'foo' = 'bar'")

Railscast #345 (which is behind a paywall) covers using hstore in more details, using the activerecord-postgres-hstore gem:

http://railscasts.com/episodes/345-hstore

Note: I haven't tried it with rails 4... YMMV.