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Decorator cache handler per view

Author:
guicifuentes
Posted:
September 9, 2008
Language:
Python
Version:
1.0
Tags:
cache view decorator
Score:
0 (after 0 ratings)

The @cache_holding decorator works in a per-function base, you can specify a list of models or just a model and the second argument is the time in seconds to be cached. You can modify the proxy class by a keyword argument so you can do cache to all kind of things, also if you want to use a prefix as key + the hash value you can specify the prefix keyword argument.

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import inspect
from django.core.cache import cache

class ModelProxy(object):
    def __init__(self, model, expiration, prefix=None):
        self._model = model
        self._expiration = expiration
        self._await = False
        self._path = []
        self._prefix = None
    
    def __getattr__(self, name):
        if name == 'objects' or self._await:
            self._path.append(name)
            self._await = True
            return self
        return getattr(self._model, name)
    
    def __call__(self, *args, **kwargs):
        hash = (args).__hash__()
        if self._prefix:
            hash = self._prefix + hash
        
        result = cache.get(hash)
        
        if not result:
            parcial = self.__dict__['_model']
            for bit in self._path:
                parcial = getattr(parcial, bit)
            result = parcial(*args, **kwargs)
            cache.set(hash, result, self._expiration)
        
        self._await = False
        self._path = []
        return result
 
import functools
def cache_holding(object_cache, time_expiration, proxy=ModelProxy, prefix=None):
    def caller(func):
        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            classnames = object_cache
            
            if not hasattr(classnames, '__iter__'):
                classnames = (classnames,)
            classnames = [class_.__name__ for class_ in classnames]
            
            try:
                frame = inspect.currentframe()
                for classname in classnames:
                    if frame.f_globals.has_key(classname):
                        old_class = frame.f_globals.get(classname)
                        frame.f_globals[classname] = proxy(old_class, time_expiration, prefix=prefix)
                result = func(*args, **kwargs)
            finally:
                del frame
                
            return result
        return wrapper
    return caller

from django.contrib.contenttypes.models import ContentType
from django.contrib.auth.models import User
@cache_holding((ContentType, User), 100)
def test():
    from django.db import connection
    connection.queries = []
    a = ContentType.objects.all()
    b = ContentType.objects.all()
    print a,b, connection.queries
    print User.news_related.all()

def do_test(n):
    for x in xrange(n):
        print "Num: %d" % x, test()

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