Can I Rebuild db/schema.rb to Include Multiple Databases Without Migrations? - ruby-on-rails

Question

I have a Rails 5 application that uses three different existing databases. No migrations were needed in this application. I want to build db/schema.rb to include all three databases, not just the main database. Executing rake db:schema:dump rebuilds the schema using the main database. I believe there is a way to do this but for some reason the way I've been searching I cannot find anything about this. All of the posts I have found discuss how to use models from different databases, not how to rebuild the schema to include all databases.

Answer 1

I started looking at this again about a month ago. After reviewing several options I found a solution created by #ostinelli that worked really well and easy to implement. This solution creates separate migrations for each database being maintained instead of putting them all in a single schema file. My goal mainly was to have a schema for each database which this accomplishes for me. There are some parts I did not implement because they were not needed.
http://www.ostinelli.net/setting-multiple-databases-rails-definitive-guide/
I created separate database yml files for each database like this:
config/database_stats.yml
development:
adapter: postgresql
encoding: utf8
host: localhost
pool: 10
database: myapp_stats_development
username: postgres
password:
test:
adapter: postgresql
encoding: utf8
host: localhost
pool: 10
database: myapp_stats_test
username: postgres
password:
production:
adapter: postgresql
encoding: utf8
url: <%= ENV["DATABASE_STATS_URL"] %>
pool: <%= ENV["DB_POOL"] || 5 %>
Then I created separate database rake tasks for each database:
lib/tasks/db_stats.rake
task spec: ["stats:db:test:prepare"]
namespace :stats do
namespace :db do |ns|
task :drop do
Rake::Task["db:drop"].invoke
end
task :create do
Rake::Task["db:create"].invoke
end
task :setup do
Rake::Task["db:setup"].invoke
end
task :migrate do
Rake::Task["db:migrate"].invoke
end
task :rollback do
Rake::Task["db:rollback"].invoke
end
task :seed do
Rake::Task["db:seed"].invoke
end
task :version do
Rake::Task["db:version"].invoke
end
namespace :schema do
task :load do
Rake::Task["db:schema:load"].invoke
end
task :dump do
Rake::Task["db:schema:dump"].invoke
end
end
namespace :test do
task :prepare do
Rake::Task["db:test:prepare"].invoke
end
end
# append and prepend proper tasks to all the tasks defined here above
ns.tasks.each do |task|
task.enhance ["stats:set_custom_config"] do
Rake::Task["stats:revert_to_original_config"].invoke
end
end
end
task :set_custom_config do
# save current vars
#original_config = {
env_schema: ENV['SCHEMA'],
config: Rails.application.config.dup
}
# set config variables for custom database
ENV['SCHEMA'] = "db_stats/schema.rb"
Rails.application.config.paths['db'] = ["db_stats"]
Rails.application.config.paths['db/migrate'] = ["db_stats/migrate"]
Rails.application.config.paths['db/seeds'] = ["db_stats/seeds.rb"]
Rails.application.config.paths['config/database'] = ["config/database_stats.yml"]
end
task :revert_to_original_config do
# reset config variables to original values
ENV['SCHEMA'] = #original_config[:env_schema]
Rails.application.config = #original_config[:config]
end
end
Then I created custom migration generators for the additional databases.
lib/generators/stats_migration_generator.rb
require 'rails/generators/active_record/migration/migration_generator'
class StatsMigrationGenerator < ActiveRecord::Generators::MigrationGenerator
source_root File.join(File.dirname(ActiveRecord::Generators::MigrationGenerator.instance_method(:create_migration_file).source_location.first), "templates")
def create_migration_file
set_local_assigns!
validate_file_name!
migration_template #migration_template, "db_stats/migrate/#{file_name}.rb"
end
end
I created database migrations for each database similar to:
rails g stats_migration create_clicks
create db_stats/migrate/20151201191642_create_clicks.rb
rake stats:db:create
rake stats:db:migrate
Then created separate database initializers for the additional databases then modified each model.
config/initializers/db_stats.rb
DB_STATS = YAML::load(ERB.new(File.read(Rails.root.join("config","database_stats.yml"))).result)[Rails.env]
class Click < ActiveRecord::Base
establish_connection DB_STATS
end
I had three databases in my application when I first wrote this question. I'm now adding another one database. I'm so grateful that #ostinelli wrote this. It made my life easier.