Plan

`orders.note` should be called `memo`. The previous deploy is still serving and still selects `note`. Put these five steps in an order that never breaks it.

8 minutes

1. 1

   Deploy code that writes both columns and reads the old one

   a deploy, not a statement

   ↑↓
2. 2

   Deploy code that reads the new column

   a deploy, not a statement

   ↑↓
3. 3

   Backfill the new column from the old

   UPDATE orders SET memo = note;

   ↑↓
4. 4

   Add the new column beside the old one

   ALTER TABLE orders ADD COLUMN memo varchar(64);

   ↑↓
5. 5

   Wait for the last instance of the old version to stop

   a deploy, not a statement

   ↑↓