cache.py

from django.core.cache import cache

class CacheTransactionMiddleware(object):
    """Queues up set and delete calls so they can be executed in bulk.

    This middleware queues up cache.set and cache.delete calls into
    one big set_many or delete_many call at the end of the request
    life cycle. This can drastically improve latency especially when
    many many calls are executed in loops.
    """
    def process_request(self, request):
        if not hasattr(request, 'cache'):
            request.cache = _CacheQueue()
    
    def process_response(self, request, response):
        request.cache.execute()

class _CacheQueue(object):
    def __init__(self):
        self.set_queue = {}
        self.delete_queue = {}
    
    def set(self, key, value, overwrite=False):
        if not overwrite and key in self.set_queue:
            raise ValueError("'%s' already queued to be set, and overwrite is set to False")
        self.set_queue[key] = value
    
    def delete(self, key, value, overwrite=False):
        if not overwrite and key in self.delete_queue:
            raise ValueError("'%s' already queued to be deleted, and overwrite is set to False")
        self.delete_queue[key] = value
    
    def execute(self):
        if self.set_queue:
            cache.set_many(self.set_queue)
            self.set_queue = {}
        if self.delete_queue:
            cache.delete_many(self.delete_queue)
            self.delete_queue = {}