#25530: Deferred SQL operations fail when a referenced table or column is
renamed
during the same migration
------------------------------+------------------------------------
Reporter: simonphilips | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.8
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 charettes):
#26461 was a duplicate caused by an implicit table rename through a
`RenameModel` operation.
I think a possible solution would be to add state dependency tracking to
`deferred_sql`. This way `RenameModel`, `AlterField`, `RenameField` and
`AlterModelTable` operations could alter it to rename the references and
`RemoveModel`, `RemoveField` operations could make sure to remove the
unnecessary statements.
For example, the `AddField` operation above would add a tuple of the form
`('CREATE INDEX ...', [(ModelState('bug', 'child', [...]), 'child'),
(ModelState('bug_parent', 'parent', [...]), 'id)]` (as it depends on both
state and fields) and the `AlterField` operation would loop over all
`editor.deferred_sql` and make sure to replace both the SQL and the state
of items depending on the model state it's about to alter. Model level
operations (`RenameModel`, `AlterModelTable`) could simply use `None` as
field to denote they depend on the model state itself.
As for the SQL replacing part I think it would make more sense to
introduce a class encapsulating the statement format string and its
dependency than naively performing `str.replace('old_table_name',
'new_table_name')` on the constructed SQL. This wrapper could also
subclass `str` in order to maintain backward compatibility with the actual
`deferred_sql` API.
Thoughts?
--
Ticket URL: <https://code.djangoproject.com/ticket/25530#comment:9>
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