Why am I getting an error when I try to update my Heroku database?

Why am I getting an error when I try to update my Heroku database?

Whenever I try any heroku rake... command I get the same error:

$ heroku rake db:setup
(in /app)
rake aborted!
uninitialized constant Rake::DSL
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2482:in `const_missing'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.2/lib/rake/tasklib.rb:8:in `<class:TaskLib>'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.2/lib/rake/tasklib.rb:6:in `<module:Rake>'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.2/lib/rake/tasklib.rb:3:in `<top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.2/lib/rake/rdoctask.rb:20:in `require'
/app/.bundle/gems/ruby/1.9.1/gems/rake-0.9.2/lib/rake/rdoctask.rb:20:in `<top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.8/lib/rails/tasks/documentation.rake:1:in `require'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.8/lib/rails/tasks/documentation.rake:1:in `<top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.8/lib/rails/tasks.rb:15:in `load'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.8/lib/rails/tasks.rb:15:in `block in <top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.8/lib/rails/tasks.rb:6:in `each'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.8/lib/rails开发者_开发问答/tasks.rb:6:in `<top (required)>'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.8/lib/rails/application.rb:215:in `require'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.8/lib/rails/application.rb:215:in `initialize_tasks'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.8/lib/rails/application.rb:139:in `load_tasks'
/app/.bundle/gems/ruby/1.9.1/gems/railties-3.0.8/lib/rails/application.rb:77:in `method_missing'
/app/Rakefile:7:in `<top (required)>'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2373:in `load'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2373:in `raw_load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2007:in `block in load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2058:in `standard_exception_handling'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:2006:in `load_rakefile'
/usr/ruby1.9.2/lib/ruby/1.9.1/rake.rb:1991:in `run'
/usr/ruby1.9.2/bin/rake:31:in `<main>'

Rakefile should include

require 'rake/dsl_definition'

There are two ways to fix this. I have a blog post about it here:

Use an older rake version, or require DSL for the newer gem.

http://codeglot.com/posts/13-you_have_already_activated_rake_0_9_2.

sadly, including require 'rake/dsl_definition' did not work for me. I am using rails 3.0.6. So I reverted back to rake 0.8.7.