pg table inheritance

pg table inheritance.rb

=begin

Gemfile:

activerecord-postgresql-extensions

=end

#db/migrate/create_answers.rb

class CreateAnswers < ActiveRecord::Migration
  def change
    create_table :answers do |t|
      t.string :desc

      t.timestamps
    end
  end
end

#db/migrate/create_special_answers.rb

class CreateSpecialAnswers < ActiveRecord::Migration
  def self.up
    create_table :special_answers, :inherits => :answers do |t|
      #t.string :desc
      t.string :misc
      #t.timestamps
    end
    #execute "ALTER TABLE special_answers INHERIT answers"
  end

  def self.down
    drop_table :special_answers
  end
end

#app/models/answer.rb

class Answer < ActiveRecord::Base
  attr_accessible :desc

  #default_scope :select => "answers.*, id, tableoid::regclass table_name"
end

#app/models/special_answer.rb

class SpecialAnswer < Answer
  set_table_name :special_answers
  attr_accessible :misc
end

#Queries

SpecialAnswer.create(:misc => "Special", :desc => "Special Desc")
SpecialAnswer.create(:misc => "Special 2", :desc => "Special Desc 2")
Answer.create(:desc => "Normal Desc 3")
Answer.create(:desc => "Normal Desc")

ap Answer.all

[
    [0] #<Answer:0xb424180> {
                :id => 2,
              :desc => "Normal Desc",
        :created_at => Fri, 19 Apr 2013 05:39:54 UTC +00:00,
        :updated_at => Fri, 19 Apr 2013 05:39:54 UTC +00:00
    },
    [1] #<Answer:0xb423e74> {
                :id => 3,
              :desc => "Normal Desc 3",
        :created_at => Fri, 19 Apr 2013 05:39:57 UTC +00:00,
        :updated_at => Fri, 19 Apr 2013 05:39:57 UTC +00:00
    },
    [2] #<Answer:0xb423b68> {
                :id => 4,
              :desc => "Special Desc",
        :created_at => Fri, 19 Apr 2013 05:39:38 UTC +00:00,
        :updated_at => Fri, 19 Apr 2013 05:39:38 UTC +00:00
    },
    [3] #<Answer:0xb42385c> {
                :id => 5,
              :desc => "Special Desc 2",
        :created_at => Fri, 19 Apr 2013 05:39:41 UTC +00:00,
        :updated_at => Fri, 19 Apr 2013 05:39:41 UTC +00:00
    }
]

ap SpecialAnswer.all
  
[
    [0] #<SpecialAnswer:0xb382ec0> {
                :id => 4,
              :desc => "Special Desc",
        :created_at => Fri, 19 Apr 2013 05:39:38 UTC +00:00,
        :updated_at => Fri, 19 Apr 2013 05:39:38 UTC +00:00,
              :misc => "Special"
    },
    [1] #<SpecialAnswer:0xb382bb4> {
                :id => 5,
              :desc => "Special Desc 2",
        :created_at => Fri, 19 Apr 2013 05:39:41 UTC +00:00,
        :updated_at => Fri, 19 Apr 2013 05:39:41 UTC +00:00,
              :misc => "Special 2"
    }
]

=begin
pgtest_development=# \d
                   List of relations
 Schema |          Name          |   Type   |  Owner   
--------+------------------------+----------+----------
 public | answers                | table    | postgres
 public | answers_id_seq         | sequence | postgres
 public | schema_migrations      | table    | postgres
 public | special_answers        | table    | postgres
 public | special_answers_id_seq | sequence | postgres
(5 rows)

pgtest_development=# \d answers
                                     Table "public.answers"
   Column   |            Type             |                      Modifiers                       
------------+-----------------------------+------------------------------------------------------
 id         | integer                     | not null default nextval('answers_id_seq'::regclass)
 desc       | character varying(255)      | 
 created_at | timestamp without time zone | not null
 updated_at | timestamp without time zone | not null
Indexes:
    "answers_pkey" PRIMARY KEY, btree (id)
Number of child tables: 1 (Use \d+ to list them.)

pgtest_development=# \d+ answers
                                                         Table "public.answers"
   Column   |            Type             |                      Modifiers                       | Storage  | Stats target | Description 
------------+-----------------------------+------------------------------------------------------+----------+--------------+-------------
 id         | integer                     | not null default nextval('answers_id_seq'::regclass) | plain    |              | 
 desc       | character varying(255)      |                                                      | extended |              | 
 created_at | timestamp without time zone | not null                                             | plain    |              | 
 updated_at | timestamp without time zone | not null                                             | plain    |              | 
Indexes:
    "answers_pkey" PRIMARY KEY, btree (id)
Child tables: special_answers
Has OIDs: no

pgtest_development=# \d special_answers
                                     Table "public.special_answers"
   Column   |            Type             |                          Modifiers                           
------------+-----------------------------+--------------------------------------------------------------
 id         | integer                     | not null default nextval('special_answers_id_seq'::regclass)
 desc       | character varying(255)      | 
 created_at | timestamp without time zone | not null
 updated_at | timestamp without time zone | not null
 misc       | character varying(255)      | 
Indexes:
    "special_answers_pkey" PRIMARY KEY, btree (id)
Inherits: answers

=end