Allow declaring pre and post migration SQL on a model's Meta class

[Nikolas]

in some cases need feature for do some SQL prior and after migration

for example:

class Meta():
   migrations.SQLBefore('truncate table logs')
   migrations.SQLAfter('insert into table logs("name") values ("initial")')

expect in migrate

RunSQL(''truncate table logs'')
.
.
.
# there what do in migrate
.
.
.
RunSQL(''insert into table logs("name") values ("initial")')

this feature very help when need some not implemented feature for example constrains or rules, or for easy create datatabse views

[Tim Graham]

You can edit migrations and add operations as needed. I don't see why the operations would need to be declared on the model.

[Simon Charette]

Also if you really want to perform operations after a CreateModel is performed you could register either pre_migrate or post_migrate receivers and inspect the plan to determine if it contains the operation you are looking for. See also #29843 which plans to add pre and post_operation signals to allow post_operation.connect(sender=CreateModel).