Hi all,
Thanks for all the help! Sorry for the incredibly slow response, but I just
wanted to give an update:
The problem was that I was trying to remove a foreign key (let's call that
foreign key "book", referencing a "book" table). I had to manually go into
the migration and add '_id' (e.g., "book_id") in every reference to that
model (odd that you need to manually update the migrations, but whatever).
Afterwards,
I was able to successfully dump the DML - which looked more or less correct.
However, the next problem was that I had unique_together constraints on
that foreign key and another existing key (e.g., unique_together("book_id",
"author_id")). I got the corresponding error message: "ValueError: Found
wrong number (0) of constraints for main_tablename(book_id, author_id)", so
I still wasn't able to complete the migration.
I worked around this by not dropping that column ("book_id" is still in the
table), and the migration finally worked. However, I'd love to get rid of
that column once and for all. So, if anyone knows a solution, please let me
know!
Dan
On Friday, October 2, 2015 at 11:26:50 PM UTC-7, James Schneider wrote:
>
> @James: Sorry, I misspoke! [field] actually corresponds to a old field in
>>> state X. Before adding the new fields in state Y, the migration is trying
>>> to remove some old fields in state X but isn't finding them. I think this
>>> means that I'm unable to re-run that migration since it's looking for state
>>> X fields to remove, but can't find them (the model is already in state Y).
>>> My confusion is in the fact that the model state wouldn't roll back to
>>> state X after the first failed transaction (like the DB did).
>>>
>>
>> That makes even less sense than your original issue. Are you sure that
>> migration X was applied properly? What versions of migrations are stored in
>> your django_migrations table? Is the latest migration listed in there for
>> your app? You should be able to find it with a raw SQL statement, something
>> like "select * from django_migrations where app = '<app_name>';".
>>
>> Does [field] currently exist in your database so that it can be removed?
>> If not, you've had issues with migrations beyond this particular i
>>
>> No. The model is all your own work. Anything you write stays written. The
>> migration system tries to implement your work. If it fails, it will roll
>> the database back to its previous state. It does nothing to your work. You
>> need to take note of the failure, decide how to fix your work and try again.
>> ssue. Were any migration files removed? Does the database match migration
>> X?
>>
>> Even better, can you also post the full traceback that you receive during
>> the failed migrations? That might lead to more clues.
>>
>
> Whoops, looks like part of my response got wrapped around Mike's by
> accident. Here's what it was supposed to say:
>
> "That makes even less sense than your original issue. Are you sure that
> migration X was applied properly? What versions of migrations are stored in
> your django_migrations table? Is the latest migration listed in there for
> your app? You should be able to find it with a raw SQL statement, something
> like "select * from django_migrations where app = '<app_name>';".
>
> Does [field] currently exist in your database so that it can be removed?
> If not, you've had issues with migrations beyond this particular issue.
> Were any migration files removed? Does the database match migration X?
>
> Even better, can you also post the full traceback that you receive during
> the failed migrations? That might lead to more clues."
>
> -James
>
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