How to use Peewee to make CASE SQL queries?

I have a table in postgres that holds a priority integer for each row. The priority needs to update whenever I add a new row or change the priority of an existing one for all of the other rows in the table.

One way to do it in pure SQL would be with a CASE query:

# example of editing priority 5 to 2 and fixing the rest
set Priority = case when Priority = 5 then 2
                    when Priority > 1 then Priority + 1
                    else Priority
               end

Question: How can I use the peewee ORM in python to facilitate this query?

I couldn’t find a way to do it in the documentation. Although the documentation offers some great examples, my use case doesn’t fit any one of the examples.

Answer

You can use peewee.Case (docs: http://docs.peewee-orm.com/en/latest/peewee/api.html#Case ). It is well documented.

class Task(Model):
    priority = IntegerField()

q = Task.update(priority=Case(None, (
    (Task.priority == 5, 2),
    (Task.priority > 1, Task.priority + 1)),
    Task.priority)
q.execute()