Python 如何使用 select_for_update 在 Django 中“获取”查询？
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How to use select_for_update to 'get' a Query in Django?
提问by Indradhanush Gupta
As the Django Documentation says, select_for_updatereturns a Queryset. But getdoes not. Now I have a query which I am sure is going to return only one tuple. But I also need to acquire locks for this transaction. So I am doing something like:
正如 Django 文档所说，select_for_update返回一个Queryset. 但get没有。现在我有一个查询，我确信它只会返回一个元组。但是我也需要为这个事务获取锁。所以我正在做类似的事情：
ob = MyModel.objects.select_for_update().filter(some conditions)
Now I need to modify some values of ob. But ob is a Queryset. This seems pretty simple, but beats me. I'm pretty new to Django. Some advice please.
现在我需要修改 ob 的一些值。但是 ob 是一个Queryset. 这看起来很简单，但打败了我。我对 Django 很陌生。请给一些建议。
采纳答案by Yuji 'Tomita' Tomita
Just call get, slice it, etc. and save as usual. The lock is in place through the transaction.
只需调用get，切片等，然后像往常一样保存。锁定通过事务就位。
ob = MyModel.objects.select_for_update().get(pk=1)
Any changes are committed at the end of the transaction (which by default through 1.5 is per-request)
任何更改都在事务结束时提交（默认情况下通过 1.5 是每个请求）
回答by Omid Raha
You canalso use select_for_updatewith get_object_or_404function:
您还可以使用select_for_updatewithget_object_or_404函数：
from django.db import transaction
from django.shortcuts import get_object_or_404
with transaction.atomic():
obj = get_object_or_404(MyModel.objects.select_for_update(), pk=pk)
# do some stuff with locked obj
