Modelset filter doesn't work in other DB except 0

[XinfuZheng]

I have multiple dbs to store data. If I specify the db 1 in model class as below:
class Param(models.Model):
Name = models.Attribute(required=True, unique=True)
class Meta:
indices = ['Name']
db = redis.Redis(host="127.0.0.1", port=6379, db='1')

The object creation is successful, the object will be created and stored in db 1. But with Param.objects.filter(Name='xxxx'), the resultset is empty.
If I don't have this db specification in model class meta, the creation and query both work.

Anyone aware of this issue?