如何在Peewee ORM中选择和限制related_name连接？

Question

I'm using Flask with the Peewee ORM in which I have defined two tables like so:

class Ticket(db.Model):
    created = DateTimeField(default=datetime.now)
    customer_uuid = CharField() # the customer's UUID gotten from App. More info comes from bunq API.
    ticket_type = ForeignKeyField(TicketType, related_name='tickets')
    active = BooleanField(default=True)

class Assign(db.Model):
    created = DateTimeField(default=datetime.now)
    ticket = ForeignKeyField(Ticket, related_name='assigned_to')
    user = ForeignKeyField(User, related_name='assigned_tickets')

In the Assign table, several users can be assigned to a ticket, but only the last one counts (ie, if a new user gets assigned, the previous ones should be disregarded). So I select the active tickets using the following:

open_tickets = Ticket.select().where(Ticket.active == True)

I now want to use this loop in my template. With every iteration however, I also want to display the assigned user. But open_ticket[0].assigned_to obviously returns several assignments, and with it several users.

Would anybody know how I can get the latest assigned user for every ticket within a loop?

Answer 1

This worked for me in Sqlite:

q = (Ticket
     .select(Ticket, Assign, User)
     .join(Assign)
     .join(User)
     .group_by(Ticket)
     .order_by(Ticket.id, Assign.id.desc()))

for ticket in q:
    print ticket.id, ticket.assign.user.username