Windows环境下Rails应用切换PostgreSQL后db:migrate执行失败

从你提供的db:migrate --trace日志来看，核心错误是PostgreSQL服务器未运行，或者没有配置为接受localhost的TCP连接，导致Rails无法建立数据库连接。下面是一步步的排查和解决方法：

1. 确认PostgreSQL服务正在运行（Windows环境） #

因为你的命令行路径是Windows系统，先检查服务状态：

• 按下Win + R，输入services.msc回车打开服务管理器
• 在列表中找到PostgreSQL相关服务（名称通常是postgresql-x64-[版本号]，比如postgresql-x64-15）
• 如果服务状态不是「正在运行」，右键点击选择「启动」；建议设置启动类型为「自动」，避免每次开机都手动启动

2. 验证PostgreSQL是否监听5432端口 #

打开命令提示符，执行以下命令：

netstat -ano | findstr :5432

如果没有返回任何结果，说明PostgreSQL没有监听5432端口，需要修改配置：

• 找到PostgreSQL安装目录下的data/postgresql.conf文件（通常在C:\Program Files\PostgreSQL\[版本号]\data）
• 找到listen_addresses配置项，修改为：

  listen_addresses = 'localhost'
  

  或者允许所有地址访问：listen_addresses = '*'
• 确认port = 5432这一行没有被注释，端口号和Rails配置一致
• 保存文件后，重启PostgreSQL服务

3. 检查Rails的database.yml配置正确性 #

确保config/database.yml中的PostgreSQL配置正确，示例如下：

default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  host: localhost
  port: 5432
  username: postgres # 默认PostgreSQL用户名是postgres
  password: your_postgres_password # 替换为你的PostgreSQL密码

development:
  <<: *default
  database: order_management_development

注意：要提前创建对应的数据库，可以用命令createdb order_management_development，或者通过pgAdmin图形工具创建。

4. 直接测试PostgreSQL连接 #

用psql命令直接测试连接，排除Rails配置问题：

psql -h localhost -p 5432 -U postgres

如果能成功进入PostgreSQL命令行，说明连接正常，再重新运行rails db:migrate；如果还是连接失败，回到步骤1和2检查服务和端口配置。

附：你提供的完整迁移日志 #

C:\Users\Jaiel\Desktop\Uebung_3_Elias_Kechter_s0555064_SoSe_2018_AI_Web_Entwicklung\order_management>rails db:migrate --trace
** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
** Invoke db:load_config (first_time)
** Execute db:load_config
** Execute db:migrate
rails aborted!
PG::ConnectionBad: could not connect to server: Connection refused (0x0000274D/10061)
        Is the server running on host "localhost" (::1) and accepting
        TCP/IP connections on port 5432?
could not connect to server: Connection refused (0x0000274D/10061)
        Is the server running on host "localhost" (127.0.0.1) and accepting
        TCP/IP connections on port 5432?
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/pg-1.0.0-x86-mingw32/lib/pg.rb:56:in `initialize'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/pg-1.0.0-x86-mingw32/lib/pg.rb:56:in `new'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/pg-1.0.0-x86-mingw32/lib/pg.rb:56:in `connect'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/postgresql_adapter.rb:697:in `connect'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/postgresql_adapter.rb:221:in `initialize'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/postgresql_adapter.rb:38:in `new'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/postgresql_adapter.rb:38:in `postgresql_connection'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:759:in `new_connection'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:803:in `checkout_new_connection'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:782:in `try_to_checkout_new_connection'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:743:in `acquire_connection'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:500:in `checkout'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:374:in `connection'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_adapters/abstract/connection_pool.rb:931:in `retrieve_connection'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_handling.rb:116:in `retrieve_connection'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/connection_handling.rb:88:in `connection'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/schema_migration.rb:20:in `table_exists?'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/schema_migration.rb:24:in `create_table'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/migration.rb:1125:in `initialize'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/migration.rb:1007:in `new'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/migration.rb:1007:in `up'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/migration.rb:985:in `migrate'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/tasks/database_tasks.rb:171:in `migrate'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/activerecord-5.1.6/lib/active_record/railties/databases.rake:58:in `block (2 levels) in <top (required)>'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/rake-12.3.1/lib/rake/task.rb:271:in `block in execute'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/rake-12.3.1/lib/rake/task.rb:271:in `each'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/rake-12.3.1/lib/rake/task.rb:271:in `execute'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/rake-12.3.1/lib/rake/task.rb:213:in `block in invoke_with_call_chain'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/2.3.0/monitor.rb:214:in `mon_synchronize'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/rake-12.3.1/lib/rake/task.rb:193:in `invoke_with_call_chain'
C:/RailsInstaller/Ruby2.3.3/lib/ruby/gems/2.3.0/gems/rake-12.3.1/lib/rake/task.rb:182:in `invoke'
C:/RailsInstaller/Ruby2.3.3/lib/

内容的提问来源于stack exchange，提问作者Ilja KO