TIL debugging Rails migrations

Notes

• If using references, the table you are referring to must already exists.
• You can debug migrations errors by looking at the issued statements in the logs.
• add_index, add_foreign_key are more flexible than t.references and its foreign_key option.
  • .. but why?
• Docs https://api.rubyonrails.org/v4.2.8/
• Docs https://dev.mysql.com/doc/refman/5.6/en/alter-table.html