Django Admin中的自定義查詢過濾器

Question

這是我的模型代碼：

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)

我想根據字符長度過濾所有報價，這是我在django admin中的查詢。

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，它返回編程錯誤不止是用作表達式的子查詢返回的一行

任何想法如何解決？

我試圖是要找到所有Quote S其中quote_text長度少於50個字符

Answer 1

告別extra問好長度

from django.db.models.functions import Length

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

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