[Django]-How to save ManyToMany field in second database

django does not support cross database relations.

Extract from cross database relations

Django doesn’t currently provide any support for foreign key or many-to-many relationships spanning multiple databases. If you have used a router to partition models to different databases, any foreign key and many-to-many relationships defined by those models must be internal to a single database.

However, as explained here you can implement post_save signal for user to have same user record on slave database. But you will have to maintain that database consistency e.g. deleting user from both databases.

Update: to save ManyToMany in different db you can try this

for i in Data.objects.all():
    back_i = i
    i.save(using='slave')
    for u in back_i.users.all():
        i.users.add(u)

A little modification to rohan’s idea… (it is assumed that ‘User’ already exists in slave database)

for item in Data.objects.all():

    new_item = item
    item_users = item.users.all()

    new_item.save(using='slave')

    for u in item_users:
       u2 = User.objects.using('slave').get(pk=u.id)
       new_item.users.add(u2)

    new_item.save(using='slave')