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In my Django application, I repeatedly run the same query on my database (e.g. every 10 seconds). I then create an MD5 sum over the queryset I receive and compare that to the MD5 sum I created in the previous run. If both are equal, the data has not changed and the web page does not need updating.
While I do this, the data in the DB might change.
However, the query returns the same queryset, apparently due to query caching.
How can I disable the query cache and explicitely execute the query on the DB ?
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For convenience, Django offers different levels of cache granularity: You can cache the output of specific views, you can cache only the pieces that are difficult to produce, or you can cache your entire site. Django also works well with “downstream” caches, such as Squid and browser-based caches.
Unless we explicitly specify another caching method in our settings file, Django defaults to local memory caching. As its name implies, this method stores cached data in RAM on the machine where Django is running. Local memory caching is fast, responsive, and thread-safe.
To use cache in Django, first thing to do is to set up where the cache will stay. The cache framework offers different possibilities - cache can be saved in database, on file system or directly in memory. Setting is done in the settings.py file of your project.
Memcached is an in-memory key-value pair store, that helps in caching dynamic websites. Django uses python-memcached binding for communication between our web application and Memcached Server.
I came across behavior that I thought was some kind of caching, but it turned out to be database transactions fooling me.
I had the problem where in another process, items were get added to the database, and I wanted to monitor progress of the other process, so I opened up a django shell and issued the following:
>>> MyData.objects.count() 74674 >>> MyData.objects.count() 74674 The value wasn't changing, even though it actually was in the database. I realized that at least with the way I had MySQL & django setup that I was in a transaction and would only see a "snapshot" of the database at the time I opened the transaction.
Since with views in django, I had autocommit behavior defined, this was fine for each view to only see a snapshot, as the next time a view was called it would be in a different transaction. But for a piece of code that was not automatically committing, it would not see any changes in the db except those that were made in this transaction.
Just thought I would toss this answer in for anyone who may come upon this situation.
To solve, commit your transaction, which can be manually done like so:
>> from django.db import transaction >> transaction.enter_transaction_management() >> transaction.commit() # Whenever you want to see new data If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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