+1
At the very least we need to provide better feedback or errors to help
isolate _where_ this is happening.
I've helped quite a number of people on IRC with this problem...
firstly, people aren't understanding _what_ the problem is, but also
discerning where it's happening is often quite difficult, even with a
full traceback.
--
C
On 26/02/16 04:29, Tim Graham wrote:
Simon proposed [0]: "I wonder if we should prevent django.db from
executing queries until django.apps.apps.ready or at least issue a
RuntimeWarning. We would have to go through deprecation but I'm pretty
sure this would uncover a lot of existing application bugs and prevent
future ones. This is related to #25454
<https://code.djangoproject.com/ticket/25454> [1] and probably a large
number of closed tickets."
We have this restriction in some places, for example: "Executing
database queries with the ORM at import time in models modules will also
trigger this exception. The ORM cannot function properly until all
models are available."
We also have a warning about using the ORM in AppConfig.ready():
"Although you can access model classes as described above, avoid
interacting with the database in your |ready()| implementation. This
includes model methods that execute queries (|save()|, |delete()|,
manager methods etc.), and also raw SQL queries via
|django.db.connection|. Your |ready()| method will run during startup of
every management command. For example, even though the test database
configuration is separate from the production settings, |manage.py test|
would still execute some queries against your *production* database!"
There's also a warning in the testing docs: "Finding data from your
production database when running tests? If your code attempts to access
the database when its modules are compiled, this will occur /before/ the
test database is set up, with potentially unexpected results. For
example, if you have a database query in module-level code and a real
database exists, production data could pollute your tests. /It is a bad
idea to have such import-time database queries in your code/ anyway -
rewrite your code so that it doesn’t do this. This also applies to
customized implementations of |ready()|."
What do you think? Prohibiting such queries might be too strict at this
point as I guess some users might rely on them. I suppose warnings could
be selectively silenced as/if needed. We could start with a warning and
ask users to let us know if they believe they have a legitimate usage.
If we don't hear anything, we could proceed with the deprecation.
Related tickets:
[0] https://code.djangoproject.com/ticket/26273
[1] https://code.djangoproject.com/ticket/25454
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