On Sun, Dec 21, 2014 at 12:55 PM, Collin Anderson <[email protected]> wrote: > > Hi Erik, > > If you want a nicer interface, I just ran manage.py inspecdb on one of my > databases and got this for the cache table. Not sure why django still does > it by hand. >
Gather `round, children, and let Grandpa fill you in on the details... :-) Although it isn't huge, Django's ORM does have an overhead. If you're looking for the general capability to query rows on a database, this overhead is a reasonable price to pay - you have a little overhead, but it's a lot easier to express complex queries. However, in the case of a cache table, you need to issue exactly 2 queries: 1) Get me the object with key X. 2) Set the value of key X. These two queries are trivial to write -- so trivial in fact, that they don't even need to rewritten as they move across database backends. They're as "vanilla" as a query can get in SQL. So - this becomes a case study in when *not* to use the ORM. We know the 2 queries that need to be issued. That SQL isn't hard to write or maintain. And using the ORM would impose a non-trivial runtime overhead - and by definition, a cache backend is supposed to be as efficient as possible. Raw SQL is the "right" answer here. (well.... not using a database backed cache backend is the *really* right answer, but I'll let that slide for the moment...) If you *do* want to do complex queries on the database cache table, the approach suggested by Collin is as good an approach as any. A managed table will give you ORM operations over an arbitrary table - include Django's own internal tables. That said, I'll also concur that the database cache backend is the wrong answer here. If you're writing a cron script, the approach I've always used is PIDfile based lock: http://unix.stackexchange.com/questions/12815/what-are-pid-and-lock-files-for Yours, Russ Magee %-) -- 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/CAJxq84-CzPsnoH4%3DT%2BfT9hEMw%2BobZpi5uHVh%3DintdcJjKMsY1Q%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
