Can you create a PR with only the fix for mediumint?

Done!

Thanks for the PR. Is it possible for you to add a test here? https://github.com/Shopify/ghostferry/blob/master/test/integration/types_test.rb

I can't get the ruby test thing to work on my machine, so I'm afraid I can't

I can't get the ruby test thing to work on my machine, so I'm afraid I can't

Do you have an error? For ruby testing, you can use nix-shell to run it if you have that. Otherwise a standard install of Ruby with bundler should just work.

I can't get the ruby test thing to work on my machine, so I'm afraid I can't

Do you have an error? For ruby testing, you can use nix-shell to run it if you have that. Otherwise a standard install of Ruby with bundler should just work.

/usr/lib/ruby/2.7.0/mkmf.rb:1050:in `block in find_library': undefined method `split' for nil:NilClass (NoMethodError)
        from /usr/lib/ruby/2.7.0/mkmf.rb:1050:in `collect'
        from /usr/lib/ruby/2.7.0/mkmf.rb:1050:in `find_library'
        from extconf.rb:87:in `<main>'

To see why this extension failed to compile, please check the mkmf.log which can be found here:

  /var/lib/gems/2.7.0/extensions/x86_64-linux/2.7.0/mysql2-0.5.3/mkmf.log

extconf failed, exit code 1

Gem files will remain installed in /var/lib/gems/2.7.0/gems/mysql2-0.5.3 for inspection.
Results logged to /var/lib/gems/2.7.0/extensions/x86_64-linux/2.7.0/mysql2-0.5.3/gem_make.out

An error occurred while installing mysql2 (0.5.3), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.5.3' --source 'https://rubygems.org/'` succeeds before bundling.

In Gemfile:
  mysql2
make: *** [Makefile:68: test-ruby] Error 5

there seems to be more issues, will look further tomorrow

you need mysql client development headers installed on your computer to install mysql2. libmysqlclient-dev for something like ubuntu.

there seems to be more issues, will look further tomorrow

Having a comprehensive integration test may help you iron out all the issue in one go.