Create idempotent migrations
October 13, 2020
When you want to write destructive migrations please use if_exists: true when you’re trying to remove a table and check for a table existence when you want to add or remove a column ActiveRecord::Base.connection.table_exists?
Case 1:
def up
drop_table :kittens, if_exists: true
end
Case 2:
def up
return unless ActiveRecord::Base.connection.table_exists?(:kittens)
add_column :kittens, :kind, :integer
end