删除特定字段中具有重复值的 Django QuerySet 对象

发布于 2024-10-27 07:19:36 字数 334 浏览 6 评论 0原文

我有这个 Django 模型（来自 Django CMS）：

class Placeholder(models.Model):
    slot = models.CharField(_("slot"), max_length=50, db_index=True)
    default_width = models.PositiveSmallIntegerField(_("width"), null=True)

我想删除具有重复“槽”值的占位符对象，仅保留每个对象的第一个并删除其他对象。

如何编写执行此操作的查询（使用 Django QuerySet API）？

原文

I have this Django model (from Django CMS):

class Placeholder(models.Model):
    slot = models.CharField(_("slot"), max_length=50, db_index=True)
    default_width = models.PositiveSmallIntegerField(_("width"), null=True)

I want to delete the Placeholder objects with a duplicate 'slot' value, keeping only the first one of each and deleting the others.

How do I write a query (using the Django QuerySet API) that does this?

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披肩女神 2024-11-03 07:19:36

您可以尝试 Torsten 解决方案，但使用字典代替，速度要快得多。

existing_slots = {}
for placeholder in Placeholder.objects.all():
    if existing_slots.get(placeholder.slot, False):
        placeholder.delete()
    else:
        existing_slots[placeholder.slot] = True

You can try Torsten solution but using a dictionary instead, is way much faster.

existing_slots = {}
for placeholder in Placeholder.objects.all():
    if existing_slots.get(placeholder.slot, False):
        placeholder.delete()
    else:
        existing_slots[placeholder.slot] = True

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ゝ杯具 2024-11-03 07:19:36

我会采用一种函数式方法，而不是执行所有这些操作的一个特定查询：

existing_slots = []
for placeholder in Placeholder.objects.all():
    if placeholder.slot in existing_slots:
        placeholder.delete()
    else:
        existing_slots.append(placeholder.slot)

I would do a functional approach, rather than one particular query which does all of this:

existing_slots = []
for placeholder in Placeholder.objects.all():
    if placeholder.slot in existing_slots:
        placeholder.delete()
    else:
        existing_slots.append(placeholder.slot)

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