How caching works in Django

Last time, I had a chance joining to a Django project. Django is a web framework written by Python. Though I've invested sometime before to study Django and been amazing with it, I haven't really done anything on Django yet. So that's a good opportunity for me to increase my Django knowledge. One of my tasks at start was to study caching supports in Django. Compare to what I knew with Ruby on Rails, I found that caching in Django is very strong and especially well-organized. So, it would be useful to put some summarizations down here.  

1. General rule
   
   
   given a URL, try finding that page in the cache
   if the page is in the cache:
       return the cached page
   else:
       generate the page
       save the generated page in the cache (for next time)
       return the generated page
   
   
2. More specific
   
   
   
   
3. Advantages and disadvantages of caching backends
   
   

   	Advantages	Disadvantages
   Memcached	- the fastest, most efficient type of cache available to Django - all cached data is stored directly in memory, so there’s no overhead of database or filesystem usage - cached data can be shared over multiple machines, so it’s excellent for scaling - being used by Facebook, Wikipedia,...	- cached data is stored in memory, so it will be lost if server crashes (but it’s not critical because cached data is just temporary) - need to have memcached daemon along the way
   In-database cached	- cached data is persistent - could use multiple databases for caching	- setup & manage multiple caching databases would be tough
   Filesystem cached	- cached data is persistent - simple to setup	- may not scale well
   Local-memory cached	- simple - not nescessary to have runing an external cache server as memcached	- no cross-process caching means it’s not particularly memory-efficient - probably not a good choice for production, just nice for development

   
   
4. Reference
   http://docs.djangoproject.com/en/1.2/topics/cache/