#27142: makemigrations fails on special database connections
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Reporter: gerricom | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.10
Severity: Release blocker | 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 shaib):
The issue is that `makemigrations` does not have a target database, while
`migrate` does. So, in order to check for consistent history,
`makemigrations` checks all databases. After this didn't work, the fix was
"well, all databases which look like they have migrations", and this still
fails.
I see two possible solutions:
1. Use the DB routing mechanism to find the list of databases which can
actually be migrated (for the relevant app), and only check consistency in
these databases. Then, users with databases which shouldn't be migrated
will have an obvious way to protect them.
2. Claim that "makemigrations" shouldn't actually touch the database --
essentially, that it's an operation whose only arguments are the
migrations and models -- and accept Tim's suggestion.
It's been a while since I looked at the migration generator, but I suspect
that it does ask the database some questions about features etc, which
would somewhat violate route 2.
I think `makemigrations` is a place where we should check consistency,
because one of the two possible reasons for inconsistent history is
erroneous editing of migration files; creating the next migration on top
of an error is something we should prevent if we can, IMO.
I also think just removing the check because of "too many problems", with
no principled reasoning behind it, is not a good option, but I won't argue
too hard for that; practicality beats purity.
--
Ticket URL: <https://code.djangoproject.com/ticket/27142#comment:4>
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