Also can't reproduce on 2-2-stable with sqlite.

I can reproduce on master w/ same error as elad though.

Looks like we should let #3274 When an ActiveRecord has a column named 'field', bad behavior happens handle this, rather than patching the symptom. Closing.

I confirm that this bug is still existing today as of version 2.3.8 (as well as 2.3.5 which I am using).

The issue is not the field name (though the example uses this weird field name 'field' which happen to be also an issue somewhere else, but this was a coincidence IMHO). The problem still exists when using a "normal" field name.

In short: "serialize :the_field_name, Hash" won't work if:

• using MySQL (I am using MySQL 5.1), as I don't have any issue with sqlite.
• the field has :null => false.
• the field's type is :text (no problem with :type => :string).

To reproduce try with the following:

db/migrate/20100729121113_create_cars.rb

class CreateCars < ActiveRecord::Migration
  def self.up
    create_table :cars do |t|
      t.string :brand, :null => false
      t.text :model_name, :null => false

      t.timestamps
    end
  end

  def self.down
    drop_table :cars
  end
end

app/models/car.rb

class Car < ActiveRecord::Base
  serialize :model_name, Hash
end

In database.yml, make sure you are using mysql (no problem with sqlite).

development:
  adapter: mysql
  encoding: utf8
  database: temp_development
  username: foo
  password: bar

db/seeds.rb

car = Car.create!(:brand => "Renault", :model_name => {"fr" => "Clio", "us" => "Foo"})

finally we can try to run the seed:

sr@sr-desktop:/tmp/apperror$ rake db:seed --trace
(in /tmp/apperror)
** Invoke db:seed (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute db:seed
rake aborted!
model_name was supposed to be a Hash, but was a String
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/attribute_methods.rb:303:in `unserialize_attribute'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/attribute_methods.rb:275:in `read_attribute'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:3181:in `send'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:3181:in `clone_attribute_value'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/dirty.rb:134:in `write_attribute'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/attribute_methods.rb:1:in `model_name='
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2906:in `send'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2906:in `assign_attributes'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2902:in `each'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2902:in `assign_attributes'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2775:in `attributes='
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/base.rb:2473:in `initialize'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/validations.rb:1069:in `new'
/var/lib/gems/1.8/gems/activerecord-2.3.8/lib/active_record/validations.rb:1069:in `create!'
/tmp/apperror/db/seeds.rb:1
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:145:in `load_without_new_constant_marking'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:145:in `load'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:521:in `new_constants_in'
/var/lib/gems/1.8/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:145:in `load'
/var/lib/gems/1.8/gems/rails-2.3.8/lib/tasks/databases.rake:211
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `call'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `execute'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `each'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `execute'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:in `invoke_with_call_chain'
/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in `invoke'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:in `run'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/var/lib/gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/var/lib/gems/1.8/gems/rake-0.8.7/bin/rake:31
/var/lib/gems/1.8/bin/rake:19:in `load'
/var/lib/gems/1.8/bin/rake:19

Here is the error "model_name was supposed to be a Hash, but was a String".

• If you try with sqlite adapter, there is no problem at all.
• If you set the 'model_name' field to :string type (in migrate file), no problem.
• With :null => true, no problem either.

FYI I am running ruby 1.8.7 on Linux.