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UseDb by David Stevenson firstname.lastname@example.org ===== USAGE This plugin allows you to use multiple databases in your rails application. You can switch the database for a model in the following manner: class MyModel < ActiveRecord::Base use_db :prefix => "secdb_", :suffix => "_cool" end "use_db" takes a prefix and a suffix (only 1 of which is required) which are prepended and appended onto the current RAILS_ENV. In the above example, I would have to make the following database entries to my database.yml: secdb_development_cool: adapter: mysql database: secdb_dev_db ... secdb_test_cool: adapater: mysql database: secdb_test_db ... It's often useful to create a single abstract model which all models using a different database extend from: class SecdbBase < ActiveRecord::Base use_db :prefix => "secdb_" self.abstract_class = true end class MyModel < SecdbBase # this model will use a different database automatically now end ========== MIGRATIONS To write a migration which executes on a different database, add the following method to your migration: class MyMigration < ActiveRecord::Migration def self.database_model return "SecdbBase" end def self.up ... end ... end The "self.database_model" call must return a string which is the name of the model whose connection you want to borrow when performing the migration. If this method is undefined, the default ActiveRecord::Base connection is used. ======= TESTING In order to test multiple databases, you must invoke a task which clones the development database structure and copies it into the test database, clearing out the existing test data. There is a single helper method which executes this task and you invoke it as follows: UseDbTest.prepare_test_db(:prefix => "secdb_") Even though it might not be the best place for it, I often place a call to this in my test helper. You don't want it to execute for every test, so put the following guards around it: unless defined?(CLONED_SEC_DB_FOR_TEST) UseDbTest.prepare_test_db(:prefix => "secdb_") CLONED_SEC_DB_FOR_TEST = true end ======== FIXTURES Fixtures will automatically be loaded into the correct database as long as the fixture name corresponds to the name of a model. For example, if I have a model called SecdbUser who uses a different database and I create a fixture file called secdb_users.yml, the fixture loader will use whatever database connection belongs to hte SecdbUser model. There is currently no other way to force a fixture to use a specific database (sorry, no join tables yet), like there is for migrations.