泡一个Django查询? [英] Pickle a django query?

问题描述

是否可以在数据库中腌制或以某种方式存储Django查询?这是行不通的:

Is it possible to pickle or somehow store a django query in the database? This won`t work :

u = User.objects.all 
import cPickle
pickled_query = cPickle.dumps(u) # and store the pickled_query in a db-field.

有什么想法吗?

已更新:

import cPickle

class CustomData(models.Model):
    name = models.CharField(max_length = 30)
    pickled_query = models.CharField(max_length = 300)

def get_custom_result(self):
    q = cPickle.loads(self.pickled_query)
    return q()

>>> cd = CustomData(name="My data", pickled_query=cPickle.dumps(User.objects.all))
>>> cd.save()
>>> for item in cd.get_custom_result(): print item
# prints all the users in the database, not printing the query result 
# when pickled, but when called like cd.get_custom_result(), that is when 
# the query is actually executed.

现在这就是我想要做的.我知道这段实际的代码不会运行，但这表明了我的意图.存储查询而不是结果，并在将来某个时候执行该查询.

Now that's what I want to do. I know this actual piece of code won`t run, but it shows my intention; to store a query, not the result, and execute that query at some point in the future.

更新#2:

>>> from django.contrib.auth.models import User
# adds two users; super and test
>>> u = User.objects.filter(username = 'test')
>>> import cPickle
>>> s = cPickle.dumps(u.query)
>>> s2 = cPickle.loads(s)
>>> o = s2.model.objects.all()
>>> o.query = s2
>>> for i in o: print i
...
super

仍未完全满意.我知道QuerySet是惰性的，因此执行s2.model.objects.all()不会执行获取所有用户的查询吗?

Still not completly satisfied. I know QuerySets are lazy so doing s2.model.objects.all() won't execute a query fetching all users?

推荐答案

有文档.基本上，如果要重新创建SQL查询，请腌制query属性，如果要对当前结果的快照进行腌制，则对整个查询集进行腌制.

There's documentation for that. Basically, pickle the query attribute if you want to recreate the SQL query, and pickle the whole queryset if you want to pickle a snapshot of the current results.

如果您腌制all()的结果而不是绑定方法，您的示例将使用后者.

Your example would do the latter, if you pickled the result of all() instead of the bound method.

这篇关于泡一个Django查询?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！