Python Django过滤器仅适用于聚合/注释

我正在尝试构造一个相当复杂的Django查询，但进展不大。我希望这里有个巫师能帮我

我有以下型号：

class Person(models.Model):
    MALE = "M"
    FEMALE = "F"
    OTHER = "O"
    UNKNOWN = "U"
    GENDER_CHOICES = (
            (MALE, "Male"),
            (FEMALE, "Female"),
            (UNKNOWN, "Other"),
    )


    firstName       = models.CharField(max_length=200, null=True, db_column="firstname")
    lastName        = models.CharField(max_length=200, null=True, db_column="lastname")

    gender          = models.CharField(max_length=1, choices=GENDER_CHOICES, default=UNKNOWN, null=True)
    dateOfBirth     = models.DateField(null=True, db_column="dateofbirth")
    dateInService   = models.DateField(null=True, db_column="dateinservice")
    photo           = models.ImageField(upload_to='person_photos', null=True) 

class SuccessionTerm(models.Model):
    originalName    = models.CharField(max_length=200, null=True, db_column="originalname")
    description     = models.CharField(max_length=200, blank=True, null=True)
    score           = models.IntegerField()

class Succession(model.Model):
    position    = models.ForeignKey(Position, to_field='positionId', db_column="position_id")
    employee    = models.ForeignKey(Employee, to_field='employeeId', db_column="employee_id")
    term        = models.ForeignKey(SuccessionTerm)

class Position(models.Model):
    positionId      = models.CharField(max_length=200, unique=True, db_column="positionid")
    title           = models.CharField(max_length=200, null=True)
    # There cannot be a DB constraint, as that would make it impossible to add the first position.
    dottedLine      = models.ForeignKey("Position", to_field='positionId', related_name="Dotted Line",
                                        null=True, db_constraint=False, db_column="dottedline_id")
    solidLine       = models.ForeignKey("Position", to_field='positionId', related_name="SolidLine", 
                                        null=True, db_constraint=False, db_column="solidline_id")
    grade           = models.ForeignKey(Grade)
    businessUnit    = models.ForeignKey(BusinessUnit, null=True, db_column="businessunit_id")
    functionalArea  = models.ForeignKey(FunctionalArea, db_column="functionalarea_id")
    location        = models.ForeignKey(Location, db_column="location_id")

class Employee(models.Model):
    person                = models.OneToOneField(Person, db_column="person_id")
    fte                   = models.IntegerField(default=100)
    dataSource            = models.ForeignKey(DataSource, db_column="datasource_id")
    talentStatus          = models.ForeignKey(TalentStatus, db_column="talentstatus_id")
    retentionRisk         = models.ForeignKey(RetentionRisk, db_column="retentionrisk_id")
    retentionRiskReason   = models.ForeignKey(RetentionRiskReason, db_column="retentionriskreason_id")
    performanceStatus     = models.ForeignKey(PerformanceStatus, db_column="performancestatus_id")
    potential             = models.ForeignKey(Potential, db_column="potential_id")
    mobility              = models.ForeignKey(Mobility, db_column="mobility_id")
    currency              = models.ForeignKey(Currency, null=True, db_column="currency_id")
    grade                 = models.ForeignKey(Grade, db_column="grade_id")
    position              = models.OneToOneField(Position, to_field='positionId', null=True, 
                                                 blank=True, db_column="position_id")
    employeeId            = models.CharField(max_length=200, unique=True, db_column="employeeid")
    dateInPosition        = models.DateField(null=True, db_column="dateinposition")

现在，我希望每个员工都能得到职位头衔、姓名，以及每个继任任期中该员工的职位在继任者表中出现的次数，以及每个员工在继任者表中出现的次数。最重要的是，我想在一个单独的查询或更具体地说，一个Django ORM语句中完成所有这些，因为我是以分页的方式完成的，但我希望能够对这些列中的任何一列的结果进行排序

到目前为止，我有：

emps = Employee.objects.all()
       .annotate(ls_st=Count('succession__term'))
       .filter(succession__term__description="ShortTerm")
       .order_by(ls_st)
       .prefetch_related('person', 'position')[lower_limit:upper_limit]

这只是继承术语中的一个，我想通过添加更多注释调用将其扩展到所有术语。 我的问题是过滤器调用在整个查询中都起作用。我只想筛选计数呼叫

我试过做一些类似CountSessional\uuuuu term\uuuuuu description'=短期的事情，但这不起作用。还有别的办法吗

事先非常感谢， 问候,

---

Linus

那么你想要的是每种不同类型的继承术语的计数？这是相当复杂的，我认为你现在不能用内置的django orm来实现这一点。除非你做了一个额外的查询

在django 1.8中，我相信您将能够使用新的查询表达式来实现这一点。但是1.8当然还没有发布，所以这对你没有帮助

同时，您可以使用非常方便的django aggregate if包

使用django aggregate if，您的查询可能如下所示：

emps = Employee.objects.annotate(
        ls_st=Count('succession__term', only=Q(succession__term__description="ShortTerm")),
        ls_lt=Count('succession__term', only=Q(succession__term__description="LongTerm")), # whatever your other term descriptions are.
        ls_ot=Count('succession__term', only=Q(succession__term__description="OtherTerm"))
    )
    .order_by('ls_st')
    .prefetch_related('person', 'position')[lower_limit:upper_limit]

免责声明：我从未使用过django aggregate if，所以我不完全确定这是否有效，但根据自述文件，它似乎应该有效