How do I force Django to ignore any caches and reload data?

I'm using the Django database models from a process that's not called from an HTTP request. The process is supposed to poll for new data every few seconds and do some processing on it. I have a loop that sleeps for a few seconds and then gets all unhandled data from the database.

What I'm seeing is that after the first fetch, the process never sees any new data. I ran a few tests and it looks like Django is caching results, even though I'm building new QuerySets every time. To verify this, I did this from a Python shell:

>>> MyModel.objects.count()
885
# (Here I added some more data from another process.)
>>> MyModel.objects.count()
885
>>> MyModel.objects.update()
0
>>> MyModel.objects.count()
1025

As you can see, adding new data doesn't change the result count. However, calling the manager's update() method seems to fix the problem.

I can't find any documentation on that update() method and have no idea what other bad things it might do.

My question is, why am I seeing this caching behavior, which contradicts what Django docs say? And how do I prevent it from happening?

python django caching

Edit Report

We've struggled a fair bit with forcing django to refresh the "cache" - which it turns out wasn't really a cache at all but an artifact due to transactions. This might not apply to your example, but certainly in django views, by default, there's an implicit call to a transaction, which mysql then isolates from any changes that happen from other processes ater you start.

we used the @transaction.commit_manually decorator and calls to transaction.commit() just before every occasion where you need up-to-date info.

As I say, this definitely applies to views, not sure whether it would apply to django code not being run inside a view.

detailed info here:

http://devblog.resolversystems.com/?p=439

answered 2010-09-23T13:36:51.630

How do I force Django to ignore any caches and reload data?

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