使用 peewee 反向外键查询

Question

I'm using the peewee orm and I would like to know how to do a reverse foreignkey query.

These are my models:

class Device(BaseModel):
    mac = CharField()
    ip = CharField()

class Metrics(BaseModel):
    device = ForeignKeyField(Device, related_name="metrics")
    sensor = CharField()
    analog = FloatField(null = True)
    timestamp = DateTimeField()

I would like to know the simplest way to get all the Devices that have a Metric with a field sensor="temperature".

I can solve it with various querys and some iteration, but I wonder if there is a more direct way to do it.

Thanks

Answer 1

One way:

Device.select().join(Metric).where(Metric.sensor == 'temperature')

Another way:

Device.select().where(fn.EXISTS(
    Metric.select().where((Metric.sensor == 'temperature') & (Metric.device == Device.id))
))