django使用一个管理器来获得一个自定义查询集

Question

我试图获得一个对象的随机列表，并将其用作表单字段的查询集。但由于它是一个列表而不是查询集，所以这是行不通的。一位朋友建议找一位经理来做这件事。但现在我不太确定从哪里开始。

我获取"查询集"列表的函数：

def get_job_list():
    all_jobs = ShortJob.objects.exclude(rarity__exact=0)
    always = ShortJob.objects.filter(rarity=0)
    pick_list = []
    job_list = []
    for job in all_jobs:
        pick_list.extend([job] * job.rarity)
    counter = 0
    while counter < 5:
        counter += 1
        job = choice(pick_list)
        job_list.append(job)
        while job in pick_list:
            pick_list.remove(job)
    for job in always:
        job_list.append(job)
    return job_list

我的表格：

class ShortJobForm(forms.Form):
    options = forms.ModelChoiceField(queryset=ShortJob.get_job_list, widget=forms.RadioSelect)

有人能告诉我解决这个问题的正确方向吗？

到目前为止，我尝试将函数重写为管理器：

class ShortJobManager(models.Manager):
""" create a random short job queryset"""
    def get_queryset(self):
        all_jobs = ShortJob.objects.exclude(rarity__exact=0)
        always = ShortJob.objects.filter(rarity=0)
        pick_list = []
        job_list = []
        for job in all_jobs:
            pick_list.extend([job] * job.rarity)
        counter = 0
        while counter < 5:
            counter += 1
            job = choice(pick_list)
            job_list.append(job)
            while job in pick_list:
                pick_list.remove(job)
        for job in always:
            job_list.append(job)
        return super(ShortJobManager, self).get_queryset(job_list)

Answer 1

您可以这样更改get_job_list((函数，使其返回一个queryset:

def get_job_list():
    all_jobs = ShortJob.objects.exclude(rarity__exact=0)
    always = ShortJob.objects.filter(rarity=0)
    pick_list = []
    pk_list = []
    for job in all_jobs:
        pick_list.extend([job.pk] * job.rarity)  # list of pks
    counter = 0
    while counter < 5:
        counter += 1
        job_pk = choice(pick_list)
        pk_list.append(job_pk)
        while job_pk in pick_list:
            pick_list.remove(job_pk)
    # pk_list is now a list of pks you can filter on
    return always.filter(pk__in=pk_list)

大致是这样的。我试图保持你的功能的目的，但可能在某些地方误解了它。要点是：

您可以选择随机pk，然后对其进行筛选，以获得查询集

Answer 2

我建议您可以使用原始qs包含UNION部分。类似这样的东西：

 ShortJob.objects.raw('SELECT * FROM myapp_shortjob WHERE rarity=0 UNION SELECT * FROM myapp_shortjob WHERE rarity!=0 ORDER BY random()')