Rails：将数据库从Postgres迁移到MongoDB

Question

My project was created using PostgresSQL but we really intend to use MongoDB, what should I change in order for that to happen?

A lot of scaffolding already took place, so we are trying to savage any of the work already done...

Answer 1

1. Remove database adapter gems from your Gemfile (mysql2, sqlite3, etc.)

2. Change your config/application.rb

Remove require 'rails/all' line and require frameworks you want to use, for example:

require "action_controller/railtie"
require "action_view/railtie"
require "action_mailer/railtie"
require "active_job/railtie"
require "action_cable/engine"
require "sprockets/railtie"
require "rails/test_unit/railtie" 

NOTE: You should be using the require snippet from the rails/all.rb file that is current with your version of Rails without the active_record railtie. Here is a link to rails/all.rb on the Rails master branch .

3. Delete your config/database.yml file, db/schema.rb and migrations (if any)

4. Delete migration check in test/test_helper.rb

5. Delete any ActiveRecord configuration from your config/environments files

Answer 2

The same situation I also I have to face . I am adding some additional points to above answer .

1) Create a file in initializers and put this code

Mongoid.load!(Rails.root.join("config/mongoid.yml"))

2) You have to remove from every model which are inheriting from ApplicationRecord and delete the application_record file.

3) If you have installed devise so you have to change
**From **

 require 'devise/orm/active_record'

to

require 'devise/orm/mongoid'

4) If you are using carrierwave so in gem file you have to replace

From

gem 'carrierwave', github: 'carrierwaveuploader/carrierwave' 

To

gem 'carrierwave-mongoid', :require => 'carrierwave/mongoid'

Answer 3

Better late than never! This should come in handy to somebody, someday!!!!

The following python-based migration framework does the job.

https://github.com/datawrangl3r/pg2mongo

Coming to the performance, the migration of each JSON object is dynamic and there shouldn't be any memory lock issues when you use the above framework.