生成随机字母数字字符串作为模型的主键 [英] Generate a random alphanumeric string as a primary key for a model

问题描述

例如：

 从django.db导入模型
 
 class MyTemporaryObject（models.Model）：
 id = AutoGenStringField（lenght = 16，primary_key = True）
 some_filed = ... 
 some_other_field = ... 
  

$ b $在我看来，关键应该是这样的Ay3kJaBdGfcadZdao03293。这是非常临时使用的。如果发生碰撞，我希望Django尝试一个新的密钥。

我想知道是否已经有了某些东西，或者我看不到的一个非常简单的解决方案（我对python和Django来说比较新）。否则我正在考虑做自己的版本的 models.AutoField ，那会是正确的方法吗？

我已经发现如何生成密钥这里，所以它不是关于字符串生成。我只想使它与一个简单的Django服务无缝工作，而不会增加代码的复杂性。

编辑：
可能的解决方案？你怎么看？

  id = models.CharField（unique = True，primary_key = True，default = StringKeyGenerator（） = False）
  

与

 $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ 
 b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b返回''.join（random.choice（string.letters + string.digits）for x in range（self.lenght））
  

我再次经历了Django文档后想到了。

解决方案

不要使该字段成为主键：

 从django.db import IntegrityError 
 
 class MyTemporaryObject（models.Model）：
 auto_pseudoid = models.CharField（max_length = 16，blank = True，editable = False，unique = True）
＃add index =它
＃blank = True是可以验证的存储之前的对象 - 保存方法将确保它获取一个值
 
＃其他字段如所需
 
 def save（self，* args，** kwargs）：
如果不是self.auto_pseudoid：
 self.auto_pseudoid = generate_random_alphanumeric（16）
＃使用你的函数如上或任何其他
 success = False 
 failures = 0 
但不成功：
 try：
 super（MyTemporaryObject，self）.save（* args，** kwargs）
除了IntegrityError：
 failures + = 1 
如果失败> 5：＃或某些其他任意截断点，事情明显错误
 raise 
 else：
＃看起来像一个碰撞，尝试另一个随机值
 self.auto_pseudoid = generate_random_alphanumeric（ 16）
 else：
 success = True 
  

这个避免的两个问题，相比之下，使用该字段作为主要的关键是：

1）Django的内置关系字段需要整数键

2）Django使用数据库中主键的存在作为一个标志， save 应更新现有记录，而不是插入新记录。这意味着如果您在主键字段中遇到冲突，则会默认覆盖该行中的其他任何值。

I would like a model to generate automatically a random alphanumeric string as its primary key when I create a new instance of it.

example:

from django.db import models

class MyTemporaryObject(models.Model):
    id = AutoGenStringField(lenght=16, primary_key=True)
    some_filed = ...
    some_other_field = ...

in my mind the key should look something like this "Ay3kJaBdGfcadZdao03293". It's for very temporary use. In case of collision I would like it Django to try a new key.

I was wondering if there was already something out there, or a very simple solution I am not seeing (I am fairly new to python and Django). Otherwise I was thinking to do my own version of models.AutoField, would that be the right approach?

I have already found how to generate the key here, so it's not about the string generation. I would just like to have it work seamlessly with a simple Django service without adding too much complexity to the code.

EDIT: Possible solution? What do you think?

id = models.CharField(unique=True, primary_key=True, default=StringKeyGenerator(), editable=False)

with

class StringKeyGenerator(object):
    def __init__(self, len=16):
        self.lenght = len
    def __call__(self):
        return ''.join(random.choice(string.letters + string.digits) for x in range(self.lenght))

I came up with it after going through the Django documentation one more time.

解决方案

Here's how I would do it without making the field a primary key:

from django.db import IntegrityError

class MyTemporaryObject(models.Model):
    auto_pseudoid = models.CharField(max_length=16, blank=True, editable=False, unique=True)
    # add index=True if you plan to look objects up by it
    # blank=True is so you can validate objects before saving - the save method will ensure that it gets a value

    # other fields as desired

    def save(self, *args, **kwargs):
        if not self.auto_pseudoid:
            self.auto_pseudoid = generate_random_alphanumeric(16)
            # using your function as above or anything else
        success = False
        failures = 0
        while not success:
            try:
                super(MyTemporaryObject, self).save(*args, **kwargs)
            except IntegrityError:
                 failures += 1
                 if failures > 5: # or some other arbitrary cutoff point at which things are clearly wrong
                     raise
                 else:
                     # looks like a collision, try another random value
                     self.auto_pseudoid = generate_random_alphanumeric(16)
            else:
                 success = True

Two problems that this avoids, compared to using the field as the primary key are that:

1) Django's built in relationship fields require integer keys

2) Django uses the presence of the primary key in the database as a sign that save should update an existing record rather than insert a new one. This means if you do get a collision in your primary key field, it'll silently overwrite whatever else used to be in the row.

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