我在第7章Michael Harl Rails Tutorial 的末尾，并在执行heroku run rake db:migrate时出现问题。它说用户＆＃39;不存在。我试图重置heroku数据库，然后迁移但仍然是同样的错误。任何想法将不胜感激。请参阅下面的完整错误跟踪。
以下是迁移文件：
class AddPasswordDigestToUsers < ActiveRecord::Migration
def change
add_column :users, :password_digest, :string
end
end
架构：
ActiveRecord::Schema.define(version: 20150824215943) do
create_table "users", force: :cascade do |t|
t.string "name"
t.string "email"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "password_digest"
end
end
和用户模型：
class User < ActiveRecord::Base
before_save { email.downcase! }
validates :name, presence: true, length: { maximum: 50 }
VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-]+(\.[a-z\d\-]+)*\.[a-z]+\z/i
validates :email, presence: true,
format: { with: VALID_EMAIL_REGEX },
uniqueness: { case_sensitive: false }
has_secure_password
validates :password, presence: true, length: { minimum: 6 }
end
完整的错误跟踪：
Running `rake db:migrate --trace` attached to terminal... up, run.1726
** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
** Invoke db:load_config (first_time)
** Execute db:load_config
** Execute db:migrate
ActiveRecord::SchemaMigration Load (1.3ms) SELECT "schema_migrations".* FROM "schema_migrations"
Migrating to AddPasswordDigestToUsers (20150824215943)
(1.0ms) BEGIN
== 20150824215943 AddPasswordDigestToUsers: migrating =========================
-- add_column(:users, :password_digest, :string)
(1.5ms) ALTER TABLE "users" ADD "password_digest" character varying
PG::UndefinedTable: ERROR: relation "users" does not exist
: ALTER TABLE "users" ADD "password_digest" character varying
(0.9ms) ROLLBACK
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:
PG::UndefinedTable: ERROR: relation "users" does not exist
: ALTER TABLE "users" ADD "password_digest" character varying/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `async_exec'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/postgresql/database_statements.rb:155:in `block in execute'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/abstract_adapter.rb:473:in `block in log'
/app/vendor/bundle/ruby/2.0.0/gems/activesupport-4.2.2/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/abstract_adapter.rb:467:in `log'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/postgresql/database_statements.rb:154:in `execute'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/abstract/schema_statements.rb:393:in `add_column'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/postgresql/schema_statements.rb:425:in `add_column'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:662:in `block in method_missing'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:632:in `block in say_with_time'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/benchmark.rb:281:in `measure'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:632:in `say_with_time'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:652:in `method_missing'
/app/db/migrate/20150824215943_add_password_digest_to_users.rb:3:in `change'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:606:in `exec_migration'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:590:in `block (2 levels) in migrate'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/benchmark.rb:281:in `measure'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:589:in `block in migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/abstract/connection_pool.rb:292:in `with_connection'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:588:in `migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:765:in `migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:995:in `block in execute_migration_in_transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:1041:in `block in ddl_transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `block in transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/abstract/transaction.rb:188:in `within_new_transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/transactions.rb:220:in `transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:1041:in `ddl_transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:994:in `execute_migration_in_transaction'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:956:in `block in migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:952:in `each'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:952:in `migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:820:in `up'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/migration.rb:798:in `migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/tasks/database_tasks.rb:137:in `migrate'
/app/vendor/bundle/ruby/2.0.0/gems/activerecord-4.2.2/lib/active_record/railties/databases.rake:44:in `block (2 levels) in <top (required)>'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/task.rb:240:in `call'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/task.rb:240:in `block in execute'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/task.rb:235:in `each'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/task.rb:235:in `execute'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/task.rb:179:in `block in invoke_with_call_chain'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/monitor.rb:211:in `mon_synchronize'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/task.rb:172:in `invoke_with_call_chain'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/task.rb:165:in `invoke'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/application.rb:150:in `invoke_task'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/application.rb:106:in `block (2 levels) in top_level'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/application.rb:106:in `each'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/application.rb:106:in `block in top_level'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/application.rb:115:in `run_with_threads'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/application.rb:100:in `top_level'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/application.rb:78:in `block in run'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/application.rb:176:in `standard_exception_handling'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/lib/rake/application.rb:75:in `run'
/app/vendor/bundle/ruby/2.0.0/gems/rake-10.4.2/bin/rake:33:in `<top (required)>'
/app/vendor/bundle/ruby/2.0.0/bin/rake:23:in `load'
/app/vendor/bundle/ruby/2.0.0/bin/rake:23:in `<main>'
答案 0 :(得分：1)
让它发挥作用。起初尝试heroku pg:reset DATABASE无济于事。
然后运行heroku run rake db:reset，然后成功迁移