Re: [Django] #27746: Database migration fail when removing a child model containing only foreignkeys in a multi-table inheritance context on MySQL

[Django]

#27746: Database migration fail when removing a child model containing only
foreignkeys in a multi-table inheritance context on MySQL
---+
 Reporter:  David CHANIAL  |Owner:  nobody
 Type:  Bug|   Status:  new
Component:  Migrations |  Version:  master
 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
---+

Comment (by Simon Charette):

 It looks like this can't be done at the optimizer level as not all
 `RemoveField` operations can be fold into `DeleteModel` ones. For example,
 the `RemoveField` operations removing many-to-many fields cannot be
 optimized (as the schema editor's `delete_model` function doesn't deal
 with intermediary table deletions) but there's no way to figure out
 whether or not a `RemoveField` operation removes a many-to-many field or
 not.

 I believe the method that requires adjustments is the
 `MigrationAutodetector.generate_deleted_models()` one.

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Re: [Django] #27746: Database migration fail when removing a child model containing only foreignkeys in a multi-table inheritance context on MySQL

[Django]

#27746: Database migration fail when removing a child model containing only
foreignkeys in a multi-table inheritance context on MySQL
---+
 Reporter:  David CHANIAL  |Owner:  nobody
 Type:  Bug|   Status:  new
Component:  Migrations |  Version:  master
 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
---+

Comment (by Simon Charette):

 Replying to [comment:3 Tim Graham]:
 > I thought the conclusion of ticket:24424#comment:11 was that it's also
 an issue with the autodetector.

 Indeed but the only way we'll be able to solve #24424 is by teaching the
 auto-detector to either issue an `AlterField` or a combination of
 equivalent operations instead of a `RemoveField` + `AddField` in order to
 convert the `id` auto-incrementing field primay key to integer foreign key
 primary key.

 There's a side discussion about the issue encountered here from comments
 19 to 22 on #24424. I believe the solution here would be to teach field
 operations to optimize the `[FieldOperation('model', 'field'),
 RemoveModel('model')]` case to `[RemoveModel("model')]`.

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Re: [Django] #27746: Database migration fail when removing a child model containing only foreignkeys in a multi-table inheritance context on MySQL

[Django]

#27746: Database migration fail when removing a child model containing only
foreignkeys in a multi-table inheritance context on MySQL
---+
 Reporter:  David CHANIAL  |Owner:  nobody
 Type:  Bug|   Status:  new
Component:  Migrations |  Version:  master
 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
---+
Changes (by Tim Graham):

 * component:  Database layer (models, ORM) => Migrations


Comment:

 I thought the conclusion of ticket:24424#comment:11 was that it's also an
 issue with the autodetector. Maybe a different one, I guess.

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Re: [Django] #27746: Database migration fail when removing a child model containing only foreignkeys in a multi-table inheritance context on MySQL

[Django]

#27746: Database migration fail when removing a child model containing only
foreignkeys in a multi-table inheritance context on MySQL
-+-
 Reporter:  David CHANIAL|Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Database layer   |  Version:  master
  (models, ORM)  |
 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
-+-
Changes (by Simon Charette):

 * status:  closed => new
 * version:  1.9 => master
 * resolution:  duplicate =>
 * stage:  Unreviewed => Accepted


Comment:

 Tim, I re-opened the ticket because I would expect the auto-detector to
 generate a single `migrations.DeleteModel` in this case.

 #24424 is related in the sense that making sure that altered tables always
 have a column would prevent the reported crash but issuing a `DROP COLUMN`
 for every single fields a model has to finally `DROP` the table doesn't
 make much sense.

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Re: [Django] #27746: Database migration fail when removing a child model containing only foreignkeys in a multi-table inheritance context on MySQL

[Django]

#27746: Database migration fail when removing a child model containing only
foreignkeys in a multi-table inheritance context on MySQL
-+-
 Reporter:  David CHANIAL|Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Database layer   |  Version:  1.9
  (models, ORM)  |
 Severity:  Normal   |   Resolution:  duplicate
 Keywords:   | Triage Stage:
 |  Unreviewed
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by Tim Graham):

 * status:  new => closed
 * resolution:   => duplicate


Comment:

 Duplicate of #24424.

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