Parent class for all specific exceptions which wrap database driver exceptions provides access to the original exception also.

Methods
N
Attributes
[R] original_exception
Class Public methods
new(message, original_exception)

Source: show | on GitHub 

# File activerecord/lib/active_record/errors.rb, line 70
def initialize(message, original_exception)
  super(message)
  @original_exception = original_exception
end