Directory problems in Chapter 6 Alembic section about building-data-science-applications-with-fastapi HOT 1 OPEN

Alembic basically works this way:

• It maintains a table alembic_revision in your database to keep track of the latest applied revision.
• When you create a migration script:
  • First, it'll make sure all the existing migrations are applied to your database. If not, it'll tell you to apply the migrations.
  • Then, it'll compare the models in your code with the table you actually have in your database
  • It'll try then to guess the operations to apply (create new table, add a column...). That's why it's not very good at detecting renames: it can't guess if you actually delete a table and create a new or rename an existing one. In those cases, you need to manually tweak the migration script
  • If there is no difference, the migration script is empty.
• When you apply the migrations, it'll apply them in order according to their revision ID. Every migration script stores the ID of the previous one, so it knows the order.

So if you want to recreate an initial migration from scratch, you need to start with an empty database and delete all existing migrations.

from building-data-science-applications-with-fastapi.