Rails migrate with different databases - ruby-on-rails

Question

I need use Devise with a existing user table in another database, so I config my database.yml:
development:
adapter: postgresql
encoding: unicode
database: almoxarifado
pool: 5
timeout: 5000
username: user
password: pass
host: localhost
users_development:
adapter: postgresql
encoding: unicode
database: portal
pool: 5
timeout: 5000
username: user
password: pass
host: localhost
schema_search_path: users
In my model I wrote this code:
class User < ActiveRecord::Base
establish_connection "users_#{Rails.env}"
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
end
When I run Rails c and call model class this work very well.
A migration file:
class AddDeviseToUsers < ActiveRecord::Migration
def self.up
ActiveRecord::Base.establish_connection "users_#{Rails.env}"
change_table(:users) do |t|
## Database authenticatable
t.string :email, :null => false, :default => ""
t.string :encrypted_password, :null => false, :default => ""
## Recoverable
t.string :reset_password_token
t.datetime :reset_password_sent_at
## Rememberable
t.datetime :remember_created_at
## Trackable
t.integer :sign_in_count, :default => 0, :null => false
t.datetime :current_sign_in_at
t.datetime :last_sign_in_at
t.string :current_sign_in_ip
t.string :last_sign_in_ip
## Confirmable
# t.string :confirmation_token
# t.datetime :confirmed_at
# t.datetime :confirmation_sent_at
# t.string :unconfirmed_email # Only if using reconfirmable
## Lockable
# t.integer :failed_attempts, :default => 0, :null => false # Only if lock strategy is :failed_attempts
# t.string :unlock_token # Only if unlock strategy is :email or :both
# t.datetime :locked_at
# Uncomment below if timestamps were not included in your original model.
# t.timestamps
end
add_index :users, :email, :unique => true
add_index :users, :reset_password_token, :unique => true
# add_index :users, :confirmation_token, :unique => true
# add_index :users, :unlock_token, :unique => true
ActiveRecord::Base.establish_connection "#{Rails.env}"
end
def self.down
# By default, we don't want to make any assumption about how to roll back a migration when your
# model already existed. Please edit below which fields you would like to remove in this migration.
raise ActiveRecord::IrreversibleMigration
end
end
But rake db:migrate return this error:
== AddDeviseToUsers: migrating =======================================
-- change_table(:users)
rake aborted!
An error has occurred, this and all later migrations canceled:
undefined method `rollback' for #<ActiveRecord::ConnectionAdapters::ClosedTransaction:0xbb06767c>
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

Answer 1

Since I spent a lot of time trying with all alternatives in this and other posts, without success, here the solution that works to me
database.yml
external_database:
adapter: postgresql
database: <%= ENV['DATABASE_NAME'] %>
username: <%= ENV['DATABASE_USERNAME'] %>
password: <%= ENV['DATABASE_PASSWORD'] %>
host: <%= ENV['DATABASE_HOST'] %>
port: <%= ENV['DATABASE_PORT'] || 5432 %>
models/yourmodel.rb
class YourModel < ActiveRecord::Base
establish_connection :external_database
end
your migration
class YourMigration < ActiveRecord::Migration
def self.up
YourModel.connection.enable_extension "plpgsql"
YourModel.connection.create_table :your_table_name, id: :uuid do |t|
t.text :title
...
end
end
def self.down
YourModel.connection.drop_table :your_table_name
end
end
Explanation:
Since the ActiveRecord::Base.establish_connection closes the connection, I'm using the connection from the model directly. Also, since I'm using UUID with the method uuid_generate_v4() as default, I enabled the extension using the same connection

Answer 2

=================================UPDATE=================================
I find a nice article talking about it: http://www.thegreatcodeadventure.com/managing-multiple-databases-in-a-single-rails-application/
=================================UPDATE=================================
I just put establish_connection out of a migrate class.
ActiveRecord::Base.establish_connection "users_#{Rails.env}"
class AddDeviseToUsers < ActiveRecord::Migration
def self.up
change_table(:users) do |t|
## Database authenticatable
t.string :email, :null => false, :default => ""
t.string :encrypted_password, :null => false, :default => ""
## Recoverable
t.string :reset_password_token
t.datetime :reset_password_sent_at
## Rememberable
t.datetime :remember_created_at
## Trackable
t.integer :sign_in_count, :default => 0, :null => false
t.datetime :current_sign_in_at
t.datetime :last_sign_in_at
t.string :current_sign_in_ip
t.string :last_sign_in_ip
## Confirmable
# t.string :confirmation_token
# t.datetime :confirmed_at
# t.datetime :confirmation_sent_at
# t.string :unconfirmed_email # Only if using reconfirmable
## Lockable
# t.integer :failed_attempts, :default => 0, :null => false # Only if lock strategy is :failed_attempts
# t.string :unlock_token # Only if unlock strategy is :email or :both
# t.datetime :locked_at
# Uncomment below if timestamps were not included in your original model.
# t.timestamps
end
add_index :users, :email, :unique => true
add_index :users, :reset_password_token, :unique => true
# add_index :users, :confirmation_token, :unique => true
# add_index :users, :unlock_token, :unique => true
end
def self.down
# By default, we don't want to make any assumption about how to roll back a migration when your
# model already existed. Please edit below which fields you would like to remove in this migration.
raise ActiveRecord::IrreversibleMigration
end
end

Answer 3

Create a method in your migration class
def self.connection
ActiveRecord::Base.establish_connection("#{Rails.env}_yourcustomenv").connection
end
took me some time to realize a method declared with self was needed. This worked on Rails 4.0

Answer 4

You were almost at the solution.
Just had to do User.connection instead of ActiveRecord::Base.establish_connection.
Take a look at the solution here:
https://stackoverflow.com/a/34292909/2499227
The ActiveRecord::Base.establish_connection way always gave me issues with schema_migrations and/or connection closing, but the Model connection runs smoothly.

Answer 5

In your config/database.yml :
development_custom_db:
database: almoxarifado
username: user
password: pass
host: localhost
Create a file contain this , in the path config/initializers/ :
module Custom
class Base < ActiveRecord::Base
self.abstract_class = true
connection_name = "#{Rails.env}_custom_db"
if Rails.application.config.database_configuration.has_key?(connection_name)
establish_connection connection_name.to_sym
end
end
class Migration < ActiveRecord::Migration
def connection
#_connection ||= Custom::Base.connection
end
end
end
Then inherit it at your migration file:
class AddDeviseToUsers < Custom::Migration
def up
change_table(:users) do |t|
end
end
end

Answer 6

Used a bit simpler approach and it worked for me on Rails 6.
class AddDimensionsToReportRecords < ActiveRecord::Migration[6.0]
def change
add_column :report_records, :sample_length, :decimal
add_column :report_records, :sample_height, :decimal
add_column :report_records, :sample_width, :decimal
end
def connection
ReportRecord.connection
end
end
And the model...
class ReportRecord < ApplicationRecord
connects_to database: { writing: :reports_db, reading: :reports_db_replica }
end