SchemaQualifiedTables
Bcdatabase::ActiveRecord::SchemaQualifiedTables
is a mix-in for ActiveRecord. It makes it easier to use AR in an application which contains models which map to tables in different schemas.
For example
Say you have an application using a legacy schema that has models like this:
class Surgery < ActiveRecord::Base
belongs_to :surgeon, :class_name => "Person", :foreign_key => "surgeon_id"
set_table_name "t_surgeries"
end
class Person < ActiveRecord::Base
set_table_name "hr.t_personnel"
end
These models map to tables in two schemas: the default schema, which contains t_surgeries
; and the schema hr
, which contains t_personnel
.
Contention
Being explicit about the schema name works for production, but what about development? You'll need separate database instances for development deployment and for test. Depending on what database you're using, this can be more or less fun (I'm looking at you, Oracle).
Also consider continuous integration: if you have several applications in CI which all refer to the hr
schema, their test data sets will stomp all over each other if you try to run them in parallel.
Solution
SchemaQualifiedTables
solves this problem by letting you configure a logical schema name for your models which is resolved into the actual schema name based on runtime configuration. In this case, you'd re-write Person
like so:
class Person < ActiveRecord::Base
set_schema :hr
set_table_name :t_personnel
end
Then, if you need to override the actual schema name in some environments, configure ActiveRecord::Base.schemas
:
# in test.rb
config.after_initialize do
ActiveRecord::Base.schemas = {
:hr => 'hr_test',
}
end
This way in the test environment, AR will map Person
to hr_test.t_personnel
. In any environment where you don't provide an explicit override, the logical schema name will be used as the actual schema name — i.e., in development and production, AR will map Person
to hr.t_personnel
.
Installing
Install the gem:
$ gem install schema_qualified_tables
If you're using rails, configure it in environment.rb:
config.gem 'schema_qualified_tables', :version => '>= 1.0.0',
:lib => 'bcdatabase/active_record/schema_qualified_tables',
:source => 'http://gemcutter.org'
Otherwise, just require 'bcdatabase/activerecord/schema_qualified_tables' sometime during initialization (before your models are loaded).
Problems?
Please send any questions to Rhett Sutphin ([email protected]).
Credits
SchemaQualifiedTables
was developed at the Northwestern University Biomedical Informatics Center.
Copyright
Copyright (c) 2009 Rhett Sutphin and Peter Nyberg. See LICENSE for details.