How to load multiple schemas into a Rails engine or app? - ruby-on-rails

Question

Seeking to move all my shared models to an engine which can be included in each of my micro apps.
This engine should provide a model layer to all our legacy data, including:
Model files
Schema files
Migrations (we're following Pivotal Labs' pattern, this isn't the issue)
Model files are being patched in automatically, that's fine.
Schema files are being monkey-patched in using Nikolay Strum's db.rake:
namespace :db do
namespace :schema do
# desc 'Dump additional database schema'
task :dump => [:environment, :load_config] do
filename = "#{Rails.root}/db/foo_schema.rb"
File.open(filename, 'w:utf-8') do |file|
ActiveRecord::Base.establish_connection("foo_#{Rails.env}")
ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
end
end
end
namespace :test do
# desc 'Purge and load foo_test schema'
task :load_schema do
# like db:test:purge
abcs = ActiveRecord::Base.configurations
ActiveRecord::Base.connection.recreate_database(abcs['foo_test']['database'], mysql_creation_options(abcs['foo_test']))
# like db:test:load_schema
ActiveRecord::Base.establish_connection('foo_test')
ActiveRecord::Schema.verbose = false
load("#{Rails.root}/db/foo_schema.rb")
end
end
end
We need rake db:create and rake db:schema:load to work,
The db.rake patches only affect db:schema:dump and db:test:load_schema (part of tests_prepare, I assume). I've attempted to patch them into db:schema:load using:
namespace :db do
# Helpers
def mysql_creation_options(config)
#charset = ENV['CHARSET'] || 'utf8'
#collation = ENV['COLLATION'] || 'utf8_unicode_ci'
{:charset => (config['charset'] || #charset), :collation => (config['collation'] || #collation)}
end
def load_schema(schema_name)
abcs = ActiveRecord::Base.configurations
ActiveRecord::Base.connection.recreate_database(abcs[schema_name+'_test']['database'], mysql_creation_options(abcs[schema_name+'_test']))
# like db:test:load_schema
ActiveRecord::Base.establish_connection(schema_name+'_test')
ActiveRecord::Schema.verbose = false
load("#{Rails.root}/db/#{schema_name}_schema.rb")
end
namespace :schema do
# desc 'Dump additional database schema'
task :dump => [:environment, :load_config] do
dump_schema = -> (schema_name) {
filename = "#{Rails.root}/db/#{schema_name}_schema.rb"
File.open(filename, 'w:utf-8') do |file|
ActiveRecord::Base.establish_connection("#{schema_name}_#{Rails.env}")
ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
end
}
dump_schema.call('kiddom')
dump_schema.call('kiddom_warehouse')
end
# When loading from schema, load these files, too
task :load => [:environment, :load_config] do
load_schema('kiddom')
load_schema('kiddom_warehouse')
end
end
namespace :test do
# desc 'Purge and load foo_test schema'
task :load_schema do
load_schema('kiddom')
load_schema('kiddom_warehouse')
end
end
end
But this gives me the error NoMethodError: undefined method 'recreate_database' for #<ActiveRecord::ConnectionAdapters::SQLite3Adapter:0x007feb6bb43558>. Apparently, this only works on Oracle-type databases?
What are the Rails commands for the underlying DROP and CREATE DATABASE sql I'm trying to affect for the extra schema.rb's?

Answer 1

You are using SQLite as your database engine. Hope that is what you want to do.
Since you are creating SQLite Database , things differ a bit from other database adapters like MySQLAdpter or Postgress.
In case of MySQL, database has to be created prior to establish a connection by spending "CREATE DATABASE ... " SQL commands. So you must create the database before establishing connection.
But in case of SQLite, since the database reside in a file and one file can contain only one database, there is no separate step to create database. An attempt to establishing a connection to the database itself will cause the database file to be created.
Hence create_database method won't work when using SQLiteAdapter. You can simply remove that line from your code.
You may have a look at the source code for the Rake task db:create
https://github.com/rails/rails/blob/f47b4236e089b07cb683ee9b7ff8b06111a0ec10/activerecord/lib/active_record/railties/databases.rake
Also, the source code for 'create' method in SQLiteDatabaseTasks. As you can see, it simply calls the establish_connection method
https://github.com/rails/rails/blob/f47b4236e089b07cb683ee9b7ff8b06111a0ec10/activerecord/lib/active_record/railties/databases.rake