まず、私はRails / Herokuの初心者なので、事前に初心者を許してください！
Railsチュートリアル（http://guides.rubyonrails.org/getting_started.html）を実行し、ブログのような「投稿」アプリを生成し、それをgithubにプッシュしてから、herokuにプッシュしました。
私のアプリはローカルでは正常に動作しますが、オンラインで実行しようとすると、「申し訳ありませんが、問題が発生しました」という赤いフォントエラーが表示されます。
これがherokuログです。
2012-06-17T18:20:21+00:00 app[web.1]: Started GET "/posts/new" for 24.246.75.91 at 2012-06-17 18:20:21 +0000
2012-06-17T18:20:21+00:00 app[web.1]: Processing by PostsController#new as HTML
2012-06-17T18:20:21+00:00 app[web.1]: Rendered posts/_form.html.erb (19.4ms)
2012-06-17T18:20:21+00:00 app[web.1]: Rendered posts/new.html.erb within layouts/application (32.8ms)
2012-06-17T18:20:21+00:00 app[web.1]: Completed 500 Internal Server Error in 39ms
2012-06-17T18:20:21+00:00 app[web.1]:
2012-06-17T18:20:21+00:00 app[web.1]: 13:
2012-06-17T18:20:21+00:00 app[web.1]: ActionView::Template::Error (undefined method `name' for #<Post:0x000000043b8e00>):
2012-06-17T18:20:21+00:00 app[web.1]: 14: <div class="field">
2012-06-17T18:20:21+00:00 app[web.1]: 15: <%= f.label :name %><br />
2012-06-17T18:20:21+00:00 app[web.1]: 18: <div class="field">
2012-06-17T18:20:21+00:00 app[web.1]: 17: </div>
2012-06-17T18:20:21+00:00 app[web.1]: 16: <%= f.text_field :name %>
2012-06-17T18:20:21+00:00 app[web.1]: 19: <%= f.label :title %><br />
2012-06-17T18:20:21+00:00 app[web.1]: app/views/posts/_form.html.erb:16:in `block in _app_views_posts__form_html_erb___4393344465537738631_33651200'
2012-06-17T18:20:21+00:00 app[web.1]: app/views/posts/_form.html.erb:1:in `_app_views_posts__form_html_erb___4393344465537738631_33651200'
2012-06-17T18:20:21+00:00 app[web.1]: app/views/posts/new.html.erb:3:in `_app_views_posts_new_html_erb___263954971377171473_37473500'
2012-06-17T18:20:21+00:00 app[web.1]: app/controllers/posts_controller.rb:35:in `new'
2012-06-17T18:20:21+00:00 app[web.1]:
一言で言えば、f.nameはデータベース内のエントリを表すオブジェクトです（fのほとんどの情報もそうです）
「未定義のメソッド`name'」エラーは、ローカルで完全に機能するため、私には奇妙に思えます。
私の仮説は、データベースがherokuと私のアプリの間で適切にリンクされていないというものです。しかし、どうすればこの問題を解決/確認できるのかわかりません。
私のアプリは現在、デフォルトで「共有データベース」を使用しています。
どのチェックについてのヒントはありますか？私が逃した何か？
編集1：データベースの移行。テーブル「投稿」はすでに「検出されている」ようです。トレースは次のとおりです。
Running rake db:migrate --trace attached to terminal... up, run.1
DEPRECATION WARNING: You have Rails 2.3-style plugins in vendor/plugins! Support for these plugins will be removed in Rails 4.0. Move them out and bundle them in your Gemfile, or fold them in to your app as lib/myplugin/* and config/initializers/myplugin.rb. See the release notes for more on this: http://weblog.rubyonrails.org/2012/01/04/rails-3-2-0-rc2-has-been-released. (called from <top (required)> at /app/Rakefile:7)
DEPRECATION WARNING: You have Rails 2.3-style plugins in vendor/plugins! Support for these plugins will be removed in Rails 4.0. Move them out and bundle them in your Gemfile, or fold them in to your app as lib/myplugin/* and config/initializers/myplugin.rb. See the release notes for more on this: http://weblog.rubyonrails.org/2012/01/04/rails-3-2-0-rc2-has-been-released. (called from <top (required)> at /app/Rakefile:7)
** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
** Invoke db:load_config (first_time)
** Invoke rails_env (first_time)
** Execute rails_env
** Execute db:load_config
** Execute db:migrate
Migrating to CreatePosts (20120418005214)
== CreatePosts: migrating ====================================================
-- create_table(:posts)
rake aborted!
An error has occurred, this and all later migrations canceled:
PG::Error: ERROR: relation "posts" already exists
: CREATE TABLE "posts" ("id" serial primary key, "name" character varying(255), "title" character varying(255), "content" text, "created_at" timestamp NOT NULL, "updated_at" timestamp NOT NULL)
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/connection_adapters/postgresql_adapter.rb:640:in `async_exec'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/connection_adapters/postgresql_adapter.rb:640:in `block in execute'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/connection_adapters/abstract_adapter.rb:280:in `block in log'
/app/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.1/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/connection_adapters/abstract_adapter.rb:275:in `log'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/connection_adapters/postgresql_adapter.rb:639:in `execute'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/connection_adapters/abstract/schema_statements.rb:170:in `create_table'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:450:in `block in method_missing'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:424:in `block in say_with_time'
/app/vendor/ruby-1.9.3-p0/lib/ruby/1.9.1/benchmark.rb:280:in `measure'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:424:in `say_with_time'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:444:in `method_missing'
/app/db/migrate/20120418005214_create_posts.rb:3:in `change'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:393:in `block (2 levels) in migrate'
/app/vendor/ruby-1.9.3-p0/lib/ruby/1.9.1/benchmark.rb:280:in `measure'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:393:in `block in migrate'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:118:in `with_connection'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:377:in `migrate'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:512:in `migrate'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:704:in `block (2 levels) in migrate'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:759:in `call'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:759:in `block in ddl_transaction'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/connection_adapters/abstract/database_statements.rb:190:in `transaction'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/transactions.rb:208:in `transaction'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:759:in `ddl_transaction'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:703:in `block in migrate'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:684:in `each'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:684:in `migrate'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:554:in `up'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/migration.rb:535:in `migrate'
/app/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.1/lib/active_record/railties/databases.rake:153:in `block (2 levels) in <top (required)>'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/task.rb:205:in `call'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/task.rb:205:in `block in execute'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/task.rb:200:in `each'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/task.rb:200:in `execute'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/task.rb:158:in `block in invoke_with_call_chain'
/app/vendor/ruby-1.9.3-p0/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/task.rb:144:in `invoke'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/application.rb:116:in `invoke_task'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `block (2 levels) in top_level'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `each'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `block in top_level'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/application.rb:88:in `top_level'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/application.rb:66:in `block in run'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/lib/rake/application.rb:63:in `run'
/app/vendor/bundle/ruby/1.9.1/gems/rake-0.9.2.2/bin/rake:33:in `<top (required)>'
/app/vendor/bundle/ruby/1.9.1/bin/rake:19:in `load'
/app/vendor/bundle/ruby/1.9.1/bin/rake:19:in `<main>'
Tasks: TOP => db:migrate
編集2：データベースを削除しようとしました。奇妙なエラー：
19:06:34[~/ED3/ed3/]>heroku run rake db:drop
Running rake db:drop attached to terminal... up, run.1
DEPRECATION WARNING: You have Rails 2.3-style plugins in vendor/plugins! Support for these plugins will be removed in Rails 4.0. Move them out and bundle them in your Gemfile, or fold them in to your app as lib/myplugin/* and config/initializers/myplugin.rb. See the release notes for more on this: http://weblog.rubyonrails.org/2012/01/04/rails-3-2-0-rc2-has-been-released. (called from <top (required)> at /app/Rakefile:7)
DEPRECATION WARNING: You have Rails 2.3-style plugins in vendor/plugins! Support for these plugins will be removed in Rails 4.0. Move them out and bundle them in your Gemfile, or fold them in to your app as lib/myplugin/* and config/initializers/myplugin.rb. See the release notes for more on this: http://weblog.rubyonrails.org/2012/01/04/rails-3-2-0-rc2-has-been-released. (called from <top (required)> at /app/Rakefile:7)
Couldn't drop mtstktqkyx : #<ActiveRecord::StatementInvalid: PG::Error: ERROR: must be owner of database mtstktqkyx
: DROP DATABASE IF EXISTS "mtstktqkyx">
編集3：CreatePostsの移行（db / migrate / ## .. ## _ create_posts.rbから）
class CreatePosts < ActiveRecord::Migration
def change
create_table :posts do |t|
t.string :name
t.string :title
t.text :content
t.timestamps
end
end
end