ORM動態創建模型類 | Django

作用：動態創建模型類，對應生成數據庫表，比如每年的日志量都非常大，或者其他表數據量特別大，需要每年分表存。

參考鏈接

# models.py
def get_entrydata_model(prefix):
    table_name = 't_entrydata_%s' % str(prefix)

    class EntrydataMetaclass(models.base.ModelBase):
        def __new__(cls, name, bases, attrs):
            name += '_' + prefix  # 這是Model的name.
            return models.base.ModelBase.__new__(cls, name, bases, attrs)

    class Entrydata(models.Model):
        __metaclass__ = EntrydataMetaclass
        target = models.ForeignKey(Target)
        datadate = models.DateTimeField("開始時間", blank=True, null=True)
        curvalue = models.DecimalField("當前值", null=True, max_digits=22, decimal_places=7)
        curvaluedate = models.DateTimeField("當前值", null=True)
        curvaluetext = models.CharField("當前值", null=True, max_length=20)
        cumulativemonth = models.DecimalField("月累計值", null=True, max_digits=22, decimal_places=7)
        cumulativequarter = models.DecimalField("季累計值", null=True, max_digits=22, decimal_places=7)
        cumulativehalfyear = models.DecimalField("半年累計值", null=True, max_digits=22, decimal_places=7)
        cumulativeyear = models.DecimalField("年累計值", null=True, max_digits=22, decimal_places=7)
        state = models.CharField("狀態", blank=True, null=True, max_length=20)
        releasestate = models.CharField('發布狀態', blank=True, default=0, max_length=10)

        @staticmethod
        def is_exists():
            return table_name in connection.introspection.table_names()

        class Meta:
            db_table = table_name

    return Entrydata

# views.py
def getmodels(modelname, year):
    try:
        from django.apps import apps

        mydata = apps.get_model('__main__', modelname + '_' + year)
    except LookupError:
        if modelname == "Entrydata":
            mydata = get_entrydata_model(year)

    if not mydata.is_exists():
        with connection.schema_editor() as schema_editor:
            schema_editor.create_model(mydata)
    return mydata

# 查詢，表不存在則創建
entry_data = getmodels("Entrydata", str('2020')).objects.exclude(state="9").filter(
                target__adminapp_id=app,
                target__cycletype=cycletype,
                target__work=work,
                datadate=now)