Rails无法使用ActiveRecord :: establish_connection连接到数据库

Question

I am opening rails console session and do:

2.6.3 :048 > ActiveRecord::Base.connected?
 => true 
2.6.3 :049 > ActiveRecord::Base.connection_pool.disconnect!
 => [] 
2.6.3 :050 > ActiveRecord::Base.connected?
 => false 
2.6.3 :051 > ActiveRecord::Base.establish_connection(:development)
 => #<ActiveRecord::ConnectionAdapters::ConnectionPool:0x00 ... >
2.6.3 :052 > ActiveRecord::Base.connected?
 => false
2.6.3 :053 > SomeModel.connection
 => #<ActiveRecord::ConnectionAdapters::PostgreSQLAdapter:0x00 ...>
2.6.3 :055 > ActiveRecord::Base.connected?
 => true

$ rails -v
Rails 5.2.3

my config/database.yml file has to be fine, because HTTP requests are working fine.

Why I cant establish connection in rails console this way?

I am asking because I have similar use of establish_connection in one of config/initializers/ file, that is configuring sneakers workers like here and there it is also returning me false on ActiveRecord::Base.connected?

Answer 1

To connect again you can use

ActiveRecord::Base.connect

AR calls establish_connection only once, for ActiveRecord::Base. All subclasses use the one connection.

You can manually call establish connection yourself on some subclasses. This is very convenient for using two databases at once, eg

class MyMainUser < ActiveRecord::Base; end 
class MyOtherDb < ActiveRecord::Base; end
class MyOtherUser < MyOtherDb; end

MyOtherDb.establish_connection ...

MyMainUser.first # uses default db
MyOtherUser.first # uses other db
You can't do queries that would cross databases though.

Answer 2

要连接，您可以使用ActiveRecord :: Base.connection，而不是可以调用Somemodel.first，它应该可以工作。