db-schema.rb

ActiveRecord::Schema.define(version: 20170104013645) do

  create_table "comments", force: :cascade do |t|
    t.integer  "stars"
    t.string   "review"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index [nil, nil], name: "index_comments_on_commentable_type_and_commentable_id"
  end

  create_table "shops", force: :cascade do |t|
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string   "name"
  end

  create_table "sites", force: :cascade do |t|
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string   "name"
  end

end

error.txt

~/code/objtest/db$ rails c
Running via Spring preloader in process 10981
SLoading development environment (Rails 5.0.1)

2.3.0 :001 > Shop.all
  Shop Load (5.6ms)  SELECT "shops".* FROM "shops"
 => #<ActiveRecord::Relation [#<Shop id: 1, created_at: "2017-01-04 01:38:16", updated_at: "2017-01-04 01:38:16", name: "Bellvue Divers">]>

2.3.0 :002 > Site.all
  Site Load (0.2ms)  SELECT "sites".* FROM "sites"
 => #<ActiveRecord::Relation [#<Site id: 1, created_at: "2017-01-04 01:37:52", updated_at: "2017-01-04 01:38:35", name: "Alki Cove 2">]>

2.3.0 :003 > Comment.all
  Comment Load (0.2ms)  SELECT "comments".* FROM "comments"
 => #<ActiveRecord::Relation []>

2.3.0 :004 > Site.first.comments.all
  Site Load (0.3ms)  SELECT  "sites".* FROM "sites" ORDER BY "sites"."id" ASC LIMIT ?  [["LIMIT", 1]]
  Comment Load (0.7ms)  SELECT "comments".* FROM "comments" WHERE "comments"."commentable_id" = ? AND "comments"."commentable_type" = ?  [["commentable_id", 1], ["commentable_type", "Site"]]
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: comments.commentable_id: SELECT "comments".* FROM "comments" WHERE "comments"."commentable_id" = ? AND "comments"."commentable_type" = ?
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/sqlite3-1.3.12/lib/sqlite3/database.rb:91:in `initialize'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/sqlite3-1.3.12/lib/sqlite3/database.rb:91:in `new'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/sqlite3-1.3.12/lib/sqlite3/database.rb:91:in `prepare'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/connection_adapters/sqlite3_adapter.rb:209:in `block in exec_query'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/connection_adapters/abstract_adapter.rb:589:in `block in log'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activesupport-5.0.1/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/connection_adapters/abstract_adapter.rb:583:in `log'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/connection_adapters/sqlite3_adapter.rb:193:in `exec_query'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/connection_adapters/abstract/database_statements.rb:377:in `select_prepared'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/connection_adapters/abstract/database_statements.rb:39:in `select_all'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/connection_adapters/abstract/query_cache.rb:95:in `select_all'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/querying.rb:39:in `find_by_sql'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/relation.rb:702:in `exec_queries'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/association_relation.rb:32:in `exec_queries'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/relation.rb:583:in `load'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activerecord-5.0.1/lib/active_record/relation.rb:260:in `records'
... 2 levels...
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/railties-5.0.1/lib/rails/commands/console_helper.rb:9:in `start'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/railties-5.0.1/lib/rails/commands/commands_tasks.rb:78:in `console'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/railties-5.0.1/lib/rails/commands/commands_tasks.rb:49:in `run_command!'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/railties-5.0.1/lib/rails/commands.rb:18:in `<top (required)>'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `block in require'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:259:in `load_dependency'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:293:in `require'
	from /Users/jblack/code/objtest/bin/rails:9:in `<top (required)>'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:287:in `load'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:287:in `block in load'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:259:in `load_dependency'
	from /Users/jblack/.rvm/gems/ruby-2.3.0/gems/activesupport-5.0.1/lib/active_support/dependencies.rb:287:in `load'
	from /Users/jblack/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from /Users/jblack/.rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from -e:1:in `<main>'2.3.0 :005 >

models-comment.rb

class Comment < ApplicationRecord
  belongs_to :commentable, polymorphic: true
end

models-shop.rb

class Shop < ApplicationRecord
  has_many :comments, as: :commentable
end

models-site.rb

class Site < ApplicationRecord
  has_many :comments, as: :commentable
end