Django N + 1查询解决方案 [英] Django N+1 query solution
问题描述
我在与...通话后访问了 http://guides.rubyonrails.org/active_record_querying.html 一个关于N + 1的对等体以及糟糕的DB查询的严重性能影响。
I visited http://guides.rubyonrails.org/active_record_querying.html after talking with a peer regarding N+1 and the serious performance implications of bad DB queries.
ActiveRecord（Rails）：
ActiveRecord (Rails):
clients = Client.includes(:address).limit(10)
客户端有地址，我打算通过客户端循环访问它们时，Rails提供包括，让它知道，并将它们添加到查询中，它消除了蝙蝠之外的9个查询。
Where client's have addresses, and I intend to access them while looping through the clients, Rails provides includes to let it know to go ahead and add them to the query, which eliminates 9 queries right off the bat.
Django：
https://github.com/lilspikey/django-batch-select 提供批量查询支持。你知道其他图书馆或技巧来实现Rails在上面提供的内容，但是在一个不太详细的庄园里（就像在19个字符修正了N + 1而非常清楚的rails示例）？另外，批次选择以同样的方式解决问题，还是这两个不同的东西？
https://github.com/lilspikey/django-batch-select provides batch query support. Do you know of other libraries or tricks to achieve what Rails provides above, but in a less verbose manor (as in the rails example wherein just 19 chars fix N+1 and is very clear)? Also, does batch-select address the concern in the same way, or are these two different things?
BTW，我不是问 select_related ，尽管它似乎是乍一看的答案。我在谈论一个情况，其中地址有一个forign键到客户端。
BTW, I'm not asking about select_related, though it may seem to be the answer at first glance. I'm speaking of a situation where address has a forign key to client.
推荐答案
可以使用prefetch_related自Django 1.4：
https://docs.djangoproject.com/en/dev/ref/models/querysets/#prefetch-related
You can do it with prefetch_related since Django 1.4: https://docs.djangoproject.com/en/dev/ref/models/querysets/#prefetch-related
如果您使用< 1.4，看看这个模块：
https://github.com/ionelmc/django-prefetch
If you're using < 1.4, have a look at this module: https://github.com/ionelmc/django-prefetch
它声称比Django的prefetch_related更灵活。详细但是很棒。
It claims to be more flexible than Django's prefetch_related. Verbose but works great.
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