#26180: Altering unique_together still sometimes missing deleted fields
-------------------------------+------------------------------------
     Reporter:  julianandrews  |                    Owner:  nobody
         Type:  Bug            |                   Status:  new
    Component:  Migrations     |                  Version:  1.9
     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 akki):

 This is happening because the `RemoveField` operation is called before
 calling the `AlterUniqueTogether` operation, resulting in the dropping of
 the field before the index.

 In the `autodetector.py`, although the `RemoveField` operations are
 created before the `AlterUniqueTogether` operations but the
 
[https://github.com/django/django/blob/20d39325ca1da57a709f3ba38299dc7b0fc4bdfb/django/db/migrations/autodetector.py#L188
 `_sort_migrations` method] corrects the order of these operations to bring
 `AlterUniqueTogether` before `RemoveField`. But the
 
[https://github.com/django/django/blob/20d39325ca1da57a709f3ba38299dc7b0fc4bdfb/django/db/migrations/autodetector.py#L190
 `_optimize_migrations` method] again reverses this order in
 `self.migrations` (which is finally what gets returned by the
 `_detect_changes` method.

 This change is related to
 
https://github.com/django/django/commit/e470f311d654267ec86f9a6325ec500345b9dff2

--
Ticket URL: <https://code.djangoproject.com/ticket/26180#comment:2>
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