#29574: Unable to create model instance after changing an abstract model to non-
abstract due to "foreign key mismatch" error
----------------------------+-------------------------------------
Reporter: josephbiko | Owner: Calvin Vu
Type: Bug | Status: assigned
Component: Migrations | Version: 2.1
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Calvin Vu):
Replying to [comment:15 Calvin Vu]:
> It seems like Bhuvnesh correctly identified the cause. A potential
solution would be to first set `C.fk` to `A.id` (which is going to be the
`id` of model 'AB', i.e., the separate tables A and B, which are connected
one-to-one with `B.a_ptr_id` when model A is made concrete), then change
model B to inherit from model A (to form model 'AB'), and then update any
existing data. Alternatively, we could also set `C.fk` to `B.a_ptr_id` as
it is also a primary key.
Nevermind, this solution probably won't work because we need B to inherit
from A to determine exactly which A instance to set C.fk to but when B
inherits from A we lose B.id so there would be no way to link C and 'AB'
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Ticket URL: <https://code.djangoproject.com/ticket/29574#comment:16>
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