rspec serialized Hash - query empty for records - ruby-on-rails

Question

I have a model called Content, with a column called dependencies, serialized as Hash:
class Content < ActiveRecord::Base
attr_accessible :dependencies
serialize :dependencies, Hash
end
This really killed my nerves for the last few hours. I'll appreciate any help/hint.
Questions:
What should be the default (empty) value in migration?
What should be the default (empty) value in FactoryGirl?
Most important - how to query in order to find empty values?
Thanks in advance!

Answer 1

What should be the default (empty) value in migration?
What should be the default (empty) value in FactoryGirl?
In both cases, the empty hash {}
Most important - how to query in order to find empty values?
Since serialized values are stored using YAML, you need to search as follows:
Content.where('dependencies = ?', {}.to_yaml)
Here's an irb transcription for my test of the above:
MacbookAir1:so1 palfvin$ rails c
Loading development environment (Rails 4.0.0)
2.0.0-p247 :001 > u = User.new(role: {})
=> #<User id: nil, role: {}, role2: nil>
2.0.0-p247 :002 > u.save
(0.3ms) begin transaction
SQL (3.3ms) INSERT INTO "users" ("role", "role2") VALUES (?, ?) [["role", "--- {}\n"], ["role2", nil]]
(1.1ms) commit transaction
=> true
2.0.0-p247 :003 > u.role
=> {}
2.0.0-p247 :004 > {}.to_yaml
=> "--- {}\n"
2.0.0-p247 :005 > u
=> #<User id: 4, role: {}, role2: nil>
2.0.0-p247 :006 > User.where(role: {}.to_yaml)
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."role" = '--- {}
'
=> #<ActiveRecord::Relation [#<User id: 3, role: {}, role2: nil>, #<User id: 4, role: {}, role2: nil>]>
2.0.0-p247 :007 >
(Note: I had created a User instance (#3) prior to posting the first version of this answer, which is why that shows up in my where as well).
And here's my user.rb file:
class User < ActiveRecord::Base
has_many :who_rated_comment_rels, foreign_key: "user_id", dependent: :destroy
serialize :role, Hash
serialize :role2
end
You can ignore the stuff not-relevant to your case (i.e. anything other than role). I hack on this project for various StackOverflow purposes.