django——实现水平分表

水平分表

# Create your models here.
from django.db import models

# 得到表模型类
# name是表名，fields是字段，app_label是你的应用名(如：flow)，module是应用下的模型（如:flow.models）,options是元类选项
def create_model(name, fields=None, app_label='', module='', options=None):
    class Meta:  # 模型类的Meta类
        pass

    if app_label:  # 必须在元类中设置app_label，相关属性可参考https://www.cnblogs.com/lcchuguo/p/4754485.html
        setattr(Meta, 'app_label', app_label)  # 更新元类的选项

    if options is not None:
        for key, value in options.items():
            setattr(Meta, key, value)  # 设置模型的属性
        attrs = {'__module__': module, 'Meta': Meta}  # 添加字段属性
    if fields:
        attrs.update(fields)  # 创建模型类对象
    return type(name, (models.Model,), attrs)  #用type动态创建类

# 同步到数据库
def install(custom_model):
    from django.db import connection
    from django.db.backends.base.schema import BaseDatabaseSchemaEditor

    """
    fix:
        editor = BaseDatabaseSchemaEditor(connection)
        try:
            editor.create_model(model=custom_model) # 会抛出个异常，不知为啥,但表会创建
        except AttributeError as error:
            print(error)
        在BaseDatabaseSchemaEditor类中有一个__enter__方法，
        需要通过with上下文打开以后deferred_sql变量才会在实例化后赋值给editor
        这样就不会有'BaseDatabaseSchemaEditor' object has no attribute 'deferred_sql'
        
    """
    with BaseDatabaseSchemaEditor(connection) as editor:
        editor.create_model(model=custom_model)


def CreateNewTab(tabdate):
    fields = {
        "name": models.CharField(max_length=30),
        "job_number": models.IntegerField(unique=True),
        "even_shift": models.CharField(max_length=1024),
        "administrator_shift": models.CharField(max_length=1024),
        "middle_shift": models.CharField(max_length=1024),
        "meeting_ops": models.CharField(max_length=1024),
        "meeting_ops_manager": models.CharField(max_length=1024),
        "checking_station": models.CharField(max_length=1024),
        '__str__': lambda self: '%s %s %s %s %s %s %s %s' % (
            self.name,
            self.job_number,
            self.even_shift,
            self.administrator_shift,
            self.middle_shift,
            self.meeting_ops,
            self.meeting_ops_manager,
            self.checking_station,
        ), }
    options = {'ordering': [
        "name",
    ], 'verbose_name': 'valued customer', }
    custom_model = create_model1(name=tabdate, fields=fields, options=options, app_label='ops_shift_',module='flow.models')
    install(custom_model)  # 同步到数据库中

# 判断表是否已经存在于数据库
def is_table_exit():
    from django.db import connection
    tables = connection.introspection.table_names()
    if table_name in tables:
        print("该表已经存在数据库中了")
        return Response("该表已经存在数据库中了")
    CreateNewTab(table_name)  # 执行创建表