Re: Odd problem: some database updates do not appear on other pages until server restart

[Fred Stluka]

Bob, On 8/19/16 8:02 AM, bobhaugen wrote: > On Friday, August 19, 2016 at 5:20:45 AM UTC-5, Michal Petrucha wrote: > > Moving the call to with_user to form.__init__ solved the problem in the form ModelChoiceField. > > These questions remain unanswered, although I intend to do a bunch more testing: > >     How pervasive is this problem? Does it affect template variables like {{ object.foreign_key_method }} where the foreign_key_method returns a queryset? I think this is very pervasive.  That is, it happened a few times to my team until we educated all developers to never use the choices, limit_choices_to, or queryset parameters of a Model field or Form field.  Instead, we always explicitly set them in __init__() instead. I assume other teams also make this mistake often. For us, this mistake caused 3 separate type of problems: 1. The problem you described:     Old data from the DB was "cached" until we restarted the     Django server, because the DB query was done only     when the Model or Form class was defined, not when each     Model or Form instance was created.  So, in answer to     your question above, yes, it would also affect template     variables that refer to the data that was loaded from the     DB when the class was defined. 2. Occasional import loops, which prevented the Django     server from starting the app, because the value of the     choices, limit_choices_to, or queryset parameter caused     another model to be loaded.  This would trip us up badly     because the import loop would often occur in our TEST or     PROD environments (Django loaded via Apache WSGI) but     not in our DEV environments (Django DEV server), since     the order of class imports could be different in those 2     different configurations.  See:     - https://groups.google.com/forum/#!topic/django-users/ONGCSO37UWY 3. There's a warning here about this mistake being able to     pollute your TEST execution with PROD data:     - https://docs.djangoproject.com/en/dev/topics/testing/overview/#the-test-database >     Is this behavior clearly documented anywhere? It didn't jump out at us.  We got burned by and it and put in some time to diagnose it.  Then we found the above link that warns of one of the problems. --Fred Fred Stluka -- mailto:f...@bristle.com -- http://bristle.com/~fred/ Bristle Software, Inc -- http://bristle.com -- Glad to be of service! Open Source: Without walls and fences, we need no Windows or Gates. -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscr...@googlegroups.com. To post to this group, send email to django-users@googlegroups.com. Visit this group at https://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/4ae3b41a-1bbb-0f9f-660a-938a80ace6d0%40bristle.com. For more options, visit https://groups.google.com/d/optout.