所以我想将我的应用程序部署到heroku，但它不支持sqlite3，所以我将生产设置为使用postgres。我认为问题是为sqlite生成的某些迁移与pg不兼容。
'heroku run rake db：migrate'的结果：
Running rake db:migrate on ⬢ ground-tree... up, run.6485
D, [2016-07-08T19:02:25.697588 #3] DEBUG -- : (0.8ms) SELECT pg_try_advisory_lock(1215818661303848385);
D, [2016-07-08T19:02:25.715589 #3] DEBUG -- : ActiveRecord::SchemaMigration Load (1.0ms) SELECT "schema_migrations".* FROM "schema_migrations"
I, [2016-07-08T19:02:25.724349 #3] INFO -- : Migrating to AddWinnerToItems (20160706115655)
D, [2016-07-08T19:02:25.726558 #3] DEBUG -- : (0.8ms) BEGIN
== 20160706115655 AddWinnerToItems: migrating =================================
-- add_column(:items, :winner_id, :references, {:foreign_key=>true})
D, [2016-07-08T19:02:25.728658 #3] DEBUG -- : (1.5ms) ALTER TABLE "items" ADD "winner_id" references
D, [2016-07-08T19:02:25.729640 #3] DEBUG -- : (0.7ms) ROLLBACK
D, [2016-07-08T19:02:25.730786 #3] DEBUG -- : (0.8ms) SELECT pg_advisory_unlock(1215818661303848385)
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:
PG::SyntaxError: ERROR: syntax error at or near "references"
LINE 1: ALTER TABLE "items" ADD "winner_id" references
^
: ALTER TABLE "items" ADD "winner_id" references
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:98:in `async_exec'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:98:in `block in execute'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:566:in `block in log'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.0.0/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:560:in `log'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:97:in `execute'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/schema_statements.rb:547:in `add_column'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/schema_statements.rb:471:in `add_column'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:845:in `block in method_missing'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:814:in `block in say_with_time'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:814:in `say_with_time'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:834:in `method_missing'
/app/db/migrate/20160706115655_add_winner_to_items.rb:3:in `change'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:788:in `exec_migration'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:772:in `block (2 levels) in migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:771:in `block in migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:398:in `with_connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:770:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:950:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1211:in `block in execute_migration_in_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1279:in `block in ddl_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `block in transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/transaction.rb:189:in `within_new_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/transactions.rb:211:in `transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1279:in `ddl_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1210:in `execute_migration_in_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1183:in `block in migrate_without_lock'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1182:in `each'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1182:in `migrate_without_lock'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1131:in `block in migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1298:in `with_advisory_lock'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1131:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1005:in `up'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:983:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/tasks/database_tasks.rb:161:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/railties/databases.rake:58:in `block (2 levels) in <top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/rake-11.2.2/exe/rake:27:in `<top (required)>'
ActiveRecord::StatementInvalid: PG::SyntaxError: ERROR: syntax error at or near "references"
LINE 1: ALTER TABLE "items" ADD "winner_id" references
^
: ALTER TABLE "items" ADD "winner_id" references
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:98:in `async_exec'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:98:in `block in execute'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:566:in `block in log'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.0.0/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:560:in `log'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:97:in `execute'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/schema_statements.rb:547:in `add_column'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/schema_statements.rb:471:in `add_column'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:845:in `block in method_missing'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:814:in `block in say_with_time'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:814:in `say_with_time'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:834:in `method_missing'
/app/db/migrate/20160706115655_add_winner_to_items.rb:3:in `change'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:788:in `exec_migration'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:772:in `block (2 levels) in migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:771:in `block in migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:398:in `with_connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:770:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:950:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1211:in `block in execute_migration_in_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1279:in `block in ddl_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `block in transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/transaction.rb:189:in `within_new_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/transactions.rb:211:in `transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1279:in `ddl_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1210:in `execute_migration_in_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1183:in `block in migrate_without_lock'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1182:in `each'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1182:in `migrate_without_lock'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1131:in `block in migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1298:in `with_advisory_lock'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1131:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1005:in `up'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:983:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/tasks/database_tasks.rb:161:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/railties/databases.rake:58:in `block (2 levels) in <top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/rake-11.2.2/exe/rake:27:in `<top (required)>'
PG::SyntaxError: ERROR: syntax error at or near "references"
LINE 1: ALTER TABLE "items" ADD "winner_id" references
^
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:98:in `async_exec'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:98:in `block in execute'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:566:in `block in log'
/app/vendor/bundle/ruby/2.3.0/gems/activesupport-5.0.0/lib/active_support/notifications/instrumenter.rb:21:in `instrument'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract_adapter.rb:560:in `log'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/database_statements.rb:97:in `execute'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/schema_statements.rb:547:in `add_column'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/postgresql/schema_statements.rb:471:in `add_column'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:845:in `block in method_missing'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:814:in `block in say_with_time'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:814:in `say_with_time'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:834:in `method_missing'
/app/db/migrate/20160706115655_add_winner_to_items.rb:3:in `change'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:788:in `exec_migration'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:772:in `block (2 levels) in migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:771:in `block in migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/connection_pool.rb:398:in `with_connection'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:770:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:950:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1211:in `block in execute_migration_in_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1279:in `block in ddl_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `block in transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/transaction.rb:189:in `within_new_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/connection_adapters/abstract/database_statements.rb:232:in `transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/transactions.rb:211:in `transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1279:in `ddl_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1210:in `execute_migration_in_transaction'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1183:in `block in migrate_without_lock'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1182:in `each'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1182:in `migrate_without_lock'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1131:in `block in migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1298:in `with_advisory_lock'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1131:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:1005:in `up'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/migration.rb:983:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/tasks/database_tasks.rb:161:in `migrate'
/app/vendor/bundle/ruby/2.3.0/gems/activerecord-5.0.0/lib/active_record/railties/databases.rake:58:in `block (2 levels) in <top (required)>'
/app/vendor/bundle/ruby/2.3.0/gems/rake-11.2.2/exe/rake:27:in `<top (required)>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)
似乎导致问题的迁移：
class AddWinnerToItems < ActiveRecord::Migration[5.0]
def change
add_column :items, :winner_id, :references, foreign_key: true
end
end
的Gemfile：
source 'https://rubygems.org'
ruby '2.3.0'
gem 'rails', '~> 5.0.0'
gem 'pg'
gem 'puma', '~> 3.0'
gem 'sass-rails', '~> 5.0'
gem 'uglifier', '>= 1.3.0'
gem 'coffee-rails', '~> 4.2'
gem 'jquery-rails'
gem 'jbuilder', '~> 2.5'
gem 'slim-rails'
gem 'bootstrap-sass'
gem 'devise'
gem 'carrierwave'
gem 'material_design_lite-sass'
gem 'ransack'
gem 'kaminari'
gem 'rolify'
gem 'business_process'
gem 'decent_exposure', '3.0.0'
gem 'friendly_id', '~> 5.1.0'
gem 'simple_form'
gem 'draper', github: 'audionerd/draper', branch: 'rails5'
gem 'activemodel-serializers-xml'
gem 'decent_decoration'
group :development, :test do
gem 'pry-rails'
gem 'dotenv-rails'
gem 'ffaker'
gem 'better_errors'
end
group :development do
gem 'binding_of_caller'
gem 'sqlite3'
gem 'letter_opener'
gem 'web-console'
gem 'listen', '~> 3.0.5'
gem 'spring'
gem 'spring-watcher-listen', '~> 2.0.0'
end
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
相关的'database.yml'部分：
default: &default
pool: 5
timeout: 5000
production:
<<: *default
database: ground_tree
adapter: postgresql
有问题：belongs_to类型（我假设pg不支持此名称），所以我将所有：belongs_to更改为：references。
现在我收到了这个错误，我不知道如何解决这个问题。
答案 0 :(得分：1)
问题在于您错误地调用了add_column，但SQLite让您可以逃脱它。来自fine manual：
add_column （table_name，column_name，type，options = {}）
将名为type的新column_name列添加到table_name[...]
add_column的第三个参数应该是列类型，但您传递:reference。 PostgreSQL中没有reference类型，所以它抱怨。 SQLite中没有reference类型，但SQLite会考虑它不知道成为text的别名的任何类型，因此它会默默地让您逃脱它。
如果使用正确的类型：
add_column :items, :winner_id, :integer, foreign_key: true
# -----------------------------^^^^^^^^
然后你会有更好的运气。
有关详细信息，请参阅Active Record Migrations指南。