Загружается в lib / initializer.rb (около строки 900 в рельсах 2.3.5):
# Loads and returns the contents of the #database_configuration_file. The
# contents of the file are processed via ERB before being sent through
# YAML::load.
def database_configuration
require 'erb'
YAML::load(ERB.new(IO.read(database_configuration_file)).result)
end