在你的 Gemfile

group :production do
  gem 'pg'
end

然后运行 ​​bundle install 并尝试在 Heroku 上部署.

Then run bundle install and try to deploy on Heroku.

如果您想在所有环境中使用 PostgreSQL 而不仅仅是在 production(推荐)中，请在 :production 组之外添加 gem 并删除其他数据库适配器，例如 sqlite.

If you want to use PostgreSQL on all environments and not only in production (recommended) add the gem outside the :production group and remove other database adapters such as sqlite.

作为旁注，您可能还想添加 rails_12factor Heroku 建议的 gem.

As a side note, you may also want to add the rails_12factor gem as suggested by Heroku.