python - django admin 中的自定义查询过滤器

Question

这是我的模型代码:

class Quote(models.Model):
    """Quote model."""
    quote_text = models.TextField(unique=True)
    author = models.ForeignKey(Author)
    topic = models.ForeignKey(Topic)
    tags = models.ManyToManyField(Tag)
    language = models.ForeignKey(Language)
    hit = models.IntegerField(default=0)
    published = models.BooleanField(default=False)
    created = models.DateTimeField(auto_now_add=True)
    modified = models.DateTimeField(auto_now=True)

我想根据字符长度过滤所有报价，这是我在 django 管理中的查询。

class QuoteCountFilter(admin.SimpleListFilter):
    """Filter based on quote_text characters count."""
    title = _('Quote Text Char Count')
    parameter_name = 'quotelength'

    def lookups(self, request, model_admin):
        return (
            ('lessthan50', _('Less than 50')),
            ('morethan50', _('More than 50')),
        )

    def queryset(self, request, queryset):
        if self.value() == 'lessthan50':
            return queryset.extra(select={"val": "SELECT id FROM web_quote WHERE character_length(quote_text) < 50"})

但是，它返回编程错误超过一行由用作表达式的子查询返回

有什么解决办法吗？

我正在尝试的是找到所有 Quote，其中 quote_text 长度小于 50 个字符

Answer 1

告别extra，向Length问好

from django.db.models.functions import Length

queryset.annotate(len=Length('quote_text').filter(len__lt=50)

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