I have recently messed up my Alembic migrations while modifying my SQLAlchemy models. To start with, I didn’t update the auto-generated migration files to name the indexes/foreign keys a name, so Alembic used its own naming scheme. This is not an actual problem until you have to modify columns that have such constraints. I have since fixed this problem, but first I had to find which column references what (I had no indexes other than primary key back then, so I could go with foreign keys only). Here is a query I put together, mostly using this article.
SELECT constraint_name, CONCAT(table_name, '.', column_name) AS 'foreign key', CONCAT(referenced_table_name, '.', referenced_column_name) AS 'references' FROM information_schema.key_column_usage WHERE referenced_table_name IS NOT NULL AND table_schema = 'my_app';
Now I could easily drop such constraints using
alembic.op.drop_constraint('users_ibfk1', 'users', type_='foreignkey') and
recreate them with
'clients', ['client_id'], ['id'])