├── README.md
└── main.py


/README.md:
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 1 | django-dynamic-tables
 2 | =====================
 3 | 
 4 | 动态创建table， 并通过 Django ORM 操作.
 5 | 
 6 | 
 7 | ## 动态的创建表
 8 | 
 9 | 动态的创建模型其实就是在运行时生成 Model 类， 这个可以通过函数实现， 通过传参(今天的日期, 如: 20181211)，然后生成新的模型类， Meta 中的 db\_table 为log\_20181211.
10 | 
11 | ```python
12 | def get_log_model(prefix):
13 |     table_name = 'log_%s' % str(prefix)
14 | 
15 |     LOG_LEVELS = (
16 |         (0, 'DEBUG'),
17 |         (10, 'INFO'),
18 |         (20, 'WARNING'),
19 |     )
20 | 
21 |     class LogMetaclass(models.base.ModelBase):
22 |         def __new__(cls, name, bases, attrs):
23 |             name += '_' + prefix  # 这是Model的name.
24 |             return models.base.ModelBase.__new__(cls, name, bases, attrs)
25 | 
26 |     class Log(models.Model):
27 |         __metaclass__ = LogMetaclass
28 |         level = models.IntegerField(choices=LOG_LEVELS)
29 |         msg = models.TextField()
30 |         time = models.DateTimeField(auto_now=True, auto_now_add=True)
31 | 
32 |         @staticmethod
33 |         def is_exists():
34 |             return table_name in connection.introspection.table_names()
35 | 
36 |         class Meta:
37 |             db_table = table_name
38 | 
39 |     return Log
40 | ```
41 | 
42 | 可以看到， 通过函数生成不同的 Log Class. 注意LogMetaclass和\_\_metaclass\_\_  , 元类可以在运行时改变模型的名字，table 的名称我们可以通过db\_table定义, 类的名称可以通过覆盖元类的方法定义。
43 | 
44 | ```python
45 | print cls.__name__
46 | Log_20181211
47 | print cls._meta.db_table
48 | log_20181211
49 | ```
50 | 
51 | ## 使用
52 | 
53 | 使用直接通过函数， 获取当前日期的 Log 模型， 然后通过is\_exists判读表是否创建， 没有创建则创建对应的表.
54 | 
55 | 
56 | ```python
57 | def index(request):
58 |     today = date.today().strftime("%Y%m%d")
59 | 
60 |     # RuntimeWarning: Model '__main__.logclasslog_' was already registered.
61 |     # Reloading models is not advised as it can lead to inconsistencies
62 |     # most notably with related models.
63 |     # 如上述警告所述, Django 不建议重复加载 Model 的定义.
64 |     # 作为 demo 可以直接通过get_log_model获取，无视警告.
65 |     # 所以这里先通过 all_models 获取已经注册的 Model,
66 |     # 如果获取不到， 再生成新的模型.
67 |     try:
68 |         cls = apps.get_model('__main__', 'Log_%s' % today)
69 |     except LookupError:
70 |         cls = get_log_model(today)
71 | 
72 |     if not cls.is_exists():
73 |         with connection.schema_editor() as schema_editor:
74 |             schema_editor.create_model(cls)
75 | 
76 |     log = cls(level=10, msg="Hello")
77 |     log.save()
78 | 
79 |     return HttpResponse('<h1>%s</h1>' % cls._meta.db_table)
80 | ```
81 | 
82 | 上面获取 cls 部分， 这里的代码先通过apps的已经注册的 all_models 获取, 否则一个模型的第二次执行定义代码就会抛出RuntimeWarning警告, 在模型的初始化函数都会注册此模型, 最好不要重复注册. 先通过 apps.get_model 获取这个模型， 如果没有获取到则通过get_log_model初始化新的模型. 这样做更加稳妥一点.
83 | 
84 | 


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/main.py:
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 1 | # -*- coding: utf-8 -*-
 2 | import sys, os
 3 | 
 4 | from datetime import date
 5 | from django.db import models
 6 | from django.db import connection
 7 | from django.apps import apps
 8 | from django.conf import settings
 9 | from django.conf.urls import url
10 | from django.core.management import execute_from_command_line
11 | from django.http import HttpResponse
12 | 
13 | settings.configure(
14 |     DEBUG=True,
15 |     SECRET_KEY='A-random-secret-key!',
16 |     ROOT_URLCONF=sys.modules[__name__],
17 |     INSTALLED_APPS=['__main__', ],
18 |     DATABASES= {
19 |         'default': {
20 |             'ENGINE': 'django.db.backends.sqlite3',
21 |             'NAME': os.path.join('./', 'db.sqlite3'),
22 |         }
23 |     }
24 | )
25 | 
26 | 
27 | def get_log_model(prefix):
28 |     table_name = 'log_%s' % str(prefix)
29 | 
30 |     LOG_LEVELS = (
31 |         (0, 'DEBUG'),
32 |         (10, 'INFO'),
33 |         (20, 'WARNING'),
34 |     )
35 | 
36 |     class LogMetaclass(models.base.ModelBase):
37 |         def __new__(cls, name, bases, attrs):
38 |             name += '_' + prefix  # 这是Model的name.
39 |             return models.base.ModelBase.__new__(cls, name, bases, attrs)
40 | 
41 |     class Log(models.Model):
42 |         __metaclass__ = LogMetaclass
43 |         level = models.IntegerField(choices=LOG_LEVELS)
44 |         msg = models.TextField()
45 |         time = models.DateTimeField(auto_now=True, auto_now_add=True)
46 | 
47 |         @staticmethod
48 |         def is_exists():
49 |             return table_name in connection.introspection.table_names()
50 | 
51 |         class Meta:
52 |             db_table = table_name
53 | 
54 |     return Log
55 | 
56 | 
57 | def index(request):
58 |     today = date.today().strftime("%Y%m%d")
59 | 
60 |     # RuntimeWarning: Model '__main__.logclasslog_' was already registered.
61 |     # Reloading models is not advised as it can lead to inconsistencies
62 |     # most notably with related models.
63 |     # 如上述错误所述, Django 不建议重复加载 Model 的定义.
64 |     # 所以这里先通过 all_models 获取已经注册的 Model,
65 |     # 如果获取不到， 再生成新的模型.
66 |     try:
67 |         cls = apps.get_model('__main__', 'Log_%s' % today)
68 |     except LookupError:
69 |         cls = get_log_model(today)
70 | 
71 |     if not cls.is_exists():
72 |         with connection.schema_editor() as schema_editor:
73 |             schema_editor.create_model(cls)
74 | 
75 |     log = cls(level=10, msg="Hello")
76 |     log.save()
77 | 
78 |     return HttpResponse('<h1>%s</h1>' % cls._meta.db_table)
79 | 
80 | 
81 | urlpatterns = [
82 |     url(r'^$', index),
83 | ]
84 | 
85 | 
86 | if __name__ == '__main__':
87 |     execute_from_command_line(sys.argv)
88 | 


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