Question

我有两个模型，即Project和Hourly。每当创建一个新项目时，我还想生成8760个新的每小时实例。

有两种方法，一种是非常昂贵的，因为8760次新数据写入数据库，即：

for i in range(0, 24):
    clock_time=i*3600
    hourly = Hourly.objects.create(project=project, clock_time=clock_time)
    hourly.save()

另一种方法是使用Django bulk_create（hourlys）方法，只要我使用默认的Hourly（）构造函数，它就可以正常工作。但是我想使用我的自定义Hourly.objects.create（）函数。但是，这给了hourly.id一个UNIQUE约束错误，即：

class HourlyManager(models.Manager):
    """"""
    def create(self, project, clock_time):
        hourly = super().create(project=project, clock_time=clock_time)
        hourly.local_civil_time = services.calc_local_civil_time(clock_time, 
                                                                 project.TMZ, 
                                                                 project.lon)
        hourly.save()
        return hourly


class ProjectManager(models.Manager):
    """"""
    def create(self, owner, project_name, TMZ, lat, lon):
        project = super().create(owner=owner, project_name=project_name, TMZ=TMZ, lat=lat, lon=lon)
        project.save()

        hourlys = []
        for i in range(0, 24):
            hourlys.append(Hourly.objects.create(project=project, clock_time=clock_time))
        Hourly.objects.bulk_create(hourlys)

        return project


class Project(models.Model):
    objects = ProjectManager()

    owner           = models.ForeignKey('auth.User', related_name='projects', on_delete=models.CASCADE)
    project_name    = models.CharField(max_length=200)
    TMZ             = models.FloatField(default=0)
    lat             = models.FloatField(default=0)  # Radians
    lon             = models.FloatField(default=0)  # Radians


class Hourly(models.Model):
    objects = HourlyManager()

    project             = models.ForeignKey(Project, related_name='hourlys', on_delete=models.CASCADE)
    clock_time          = models.FloatField(default=0) 
    local_civil_time    = models.FloatField(default=0)

Answer 1

当您调用hourlys.append(Hourly.objects.create(project=project, clock_time=clock_time))时，已在数据库中创建Hourly模型的对象，并且您将该对象附加到hourlys列表中。该列表中的每个对象都已与其关联id。因此，当您尝试在下一行中执行bulk_create时，django会尝试创建具有相同ID的新对象，从而无法使用唯一约束。

Answer 2

@arne，这是bulk_create的错误方法。

    hourlys = []
    for i in range(0, 24):
        hourlys.append(Hourly.objects.create(project=project, 
     clock_time=clock_time))
     Hourly.objects.bulk_create(hourlys)

正确的方法是将属性传递给Hourly对象，创建一个列表。压缩版本如下所示。

hourlys = [Hourly(project=project, clock_time=i*3600) for i in range(24)]
hourlys_objects = Hourly.objects.bulk_create(hourlys)

有关详情，请参阅link here

如上所述，当您调用Hourly.objects.create时，会创建对象（对数据库的命中也会影响使用bulk_create优化的目的）。

Answer 3

这是我最终得到的，似乎工作正常。我在ProjectManager中使用bulk_create，而不是为Hourly模型创建一个名为create（）的新类方法（@classmethod）。这解决了每小时不具有唯一ID的问题。我不是为什么，但似乎确实很好。

class ProjectManager(models.Manager):
    """"""
    def create(self, owner, project_name, TMZ, lat, lon):
        project = super().create(owner=owner, project_name=project_name, TMZ=TMZ, lat=lat, lon=lon) # "CREATED BY PROJECTMANAGER"
        project.save()

        hourlys = []
        for i in range(0, 24):
            clock_time = i*3600
            hourlys.append(Hourly.create(project=project, clock_time=clock_time))
        Hourly.objects.bulk_create(hourlys)
        return project


class Project(models.Model):
    objects = ProjectManager()

    owner           = models.ForeignKey('auth.User', related_name='projects', on_delete=models.CASCADE)
    project_name    = models.CharField(max_length=200)
    TMZ             = models.FloatField(default=0)
    lat             = models.FloatField(default=0)  # Radians
    lon             = models.FloatField(default=0)  # Radians


class Hourly(models.Model):
    #objects = HourlyManager()

    project             = models.ForeignKey(Project, related_name='hourlys', on_delete=models.CASCADE)
    clock_time          = models.FloatField(default=0) # One year = 31557600 seconds primary_key=True, 
    declination         = models.FloatField(default=0)
    local_civil_time    = models.FloatField(default=0)
    equation_of_time    = models.FloatField(default=0)
    solar_time          = models.FloatField(default=0)
    solar_hour_angle    = models.FloatField(default=0)

    @classmethod
    def create(cls, project, clock_time):
        hourly = cls(project=project, clock_time=clock_time)
        hourly.declination      = services.calc_declination(clock_time)
        hourly.local_civil_time = services.calc_local_civil_time(clock_time, 
                                                                 project.TMZ, 
                                                                 project.lon)
        hourly.equation_of_time = services.calc_equation_of_time(clock_time)
        hourly.solar_time       = services.calc_solar_time(hourly.local_civil_time,
                                                           hourly.equation_of_time)
        hourly.solar_hour_angle = services.calc_solar_hour_angle(hourly.solar_time)
        return hourly

使用Django bulk_create使UNIQUE约束失败：solgeo_hourly.id

3 个答案: