UUIDField的“默认”属性是否照顾到唯一性？ [英] Does UUIDField's 'default' attribute takes care of the uniqueness?
问题描述
我刚刚跳入Django进行了一个快速项目，我发现其中有一个。
I just jumped into Django for a quick project and I figured there is a UUIDField in the models.
我将其用于每个模型都必须公开对象的外部id字段。 default 参数是否可以处理唯一性，还是必须在保存时将其写入？我的意思是，我知道几乎没有价值冲突的机会，而只是想知道它是如何在内部完成的
I am using this for an external id field that every model will have to expose the object. Will the default parameter handle the uniqueness or do I have to write it in the save? I mean I know there is practically no chance of values colliding, but just to know how it is done internally
推荐答案
UUID模块每次如何保证唯一值？
RFC 4122 （UUID模块规范）指定了三种生成UUID的算法：
RFC 4122(UUID module specification) specifies three algorithms to generate UUIDs:
- 使用IEEE 802 MAC地址作为唯一性来源
- 使用伪随机数
- 将知名字符串与加密哈希结合使用
在所有情况下，种子值都与系统时钟和时钟序列值结合在一起（以保持唯一性）以防时钟倒转）。结果，根据上述机制生成的UUID将与已经或将要分配的所有其他UUID保持唯一。
In all cases the seed value is combined with the system clock and a clock sequence value (to maintain uniqueness in case the clock was set backwards). As a result, the UUIDs generated according to the mechanisms above will be unique from all other UUIDs that have been or will be assigned.
来自RFC 4122 摘要：
Taken from RFC 4122 Abstract:
UUID为128位长，可以保证空间和
时间的唯一性。
A UUID is 128 bits long, and can guarantee uniqueness across space and time.
注意：由于UUIDS的唯一性属性，Django内部没有进行检查（如@FlipperPA所述）检查是否已经存在另一个具有相同 uuid 的对象。
Note: Due to this uniqueness property of UUIDS, there is no check done by Django internally (as mentioned by @FlipperPA) to check if there already exists another object with the same uuid.
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