Export local db to JSON

gistfile1.rb

namespace :json do
  desc "Export all data to JSON files"
  task :export => :environment do
    Rails.application.eager_load!

    ActiveRecord::Base.descendants.each do |model|
      file = File.open(File.join(Rails.root, "db", "export", "#{model.table_name}.json"), 'w')
      file.write model.all.to_json
      file.close
    end
  end

  desc "Import all data from JSON files"
  task :import => :environment do
    Dir["./db/export/*.json"].each do |file|

      table_name = file.split('/').last.split('.').first
      class_type = table_name.classify.constantize
      models = JSON.parse(File.read(file))
      models.each do |model|
        model_var = class_type.new(model)
        model_var.save
      end
      ActiveRecord::Base.connection.reset_pk_sequence!(table_name)
    end
  end

end

This rake task should be placed in the Rails app lib/tasks directory. It can then be run as:

rake json:export

It will produce JSON which you can check into git. Then push to Heroku. Then on Heroku run:

rake json:import

To import the data from JSON into the db.

Note: Use at your own risk. Not meant for live production apps.

👍 Nice one.

For Rails 5 this should be updated to use ApplicationRecord.descendants instead of ActiveRecord::Base.descendants

+1 @rchasman for Rails 5 note. Also I think it should be said that this doesn't work on a MySQL database. (Postgres only?)

Thanks for this! Also, you probably want to exclude the sessions table :)

A few gotchas I discovered:

• You may want to exclude the sessions table (and maybe others)
• If your model defines as_json you may not get all the data you expect
• If your model defines default query behavior (like paranoia gem with deleted_at), you may not get all the data you expect

UPDATE: https://gist.github.com/synth/afe534267d79c7cfc696e0ec7a73c9d1
Made the script a bit more robust for larger data sets :)