#33543: The behaviour of nulls_first and nulls_last is surprising and confusing.
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Reporter: Gordon | Owner: nobody
Wrigley |
Type: | Status: new
Uncategorized |
Component: Database | Version: 3.2
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Consider the following:
{{{
In [11]: [tv.published_at for tv in
TemplateVersion.objects.order_by(F("published_at").desc(nulls_first=True))]
Out[11]:
[None,
datetime.datetime(2022, 2, 25, 13, 0, 12, 91916, tzinfo=<UTC>),
datetime.datetime(2022, 2, 21, 10, 18, 0, 169248, tzinfo=<UTC>)]
In [12]: [tv.published_at for tv in
TemplateVersion.objects.order_by(F("published_at").desc(nulls_first=False))]
Out[12]:
[None,
datetime.datetime(2022, 2, 25, 13, 0, 12, 91916, tzinfo=<UTC>),
datetime.datetime(2022, 2, 21, 10, 18, 0, 169248, tzinfo=<UTC>)]
In [13]: [tv.published_at for tv in
TemplateVersion.objects.order_by(F("published_at").desc(nulls_last=True))]
Out[13]:
[datetime.datetime(2022, 2, 25, 13, 0, 12, 91916, tzinfo=<UTC>),
datetime.datetime(2022, 2, 21, 10, 18, 0, 169248, tzinfo=<UTC>),
None]
In [14]: [tv.published_at for tv in
TemplateVersion.objects.order_by(F("published_at").desc(nulls_last=False))]
Out[14]:
[None,
datetime.datetime(2022, 2, 25, 13, 0, 12, 91916, tzinfo=<UTC>),
datetime.datetime(2022, 2, 21, 10, 18, 0, 169248, tzinfo=<UTC>)]
}}}
Observe how `nulls_first=False` still puts the nulls first.
This happens because they both default False and when they are both False
it lets the DB decide.
This is surprising behaviour, it also makes changing the null positioning
based on a variable more awkward than it needs to be.
I think it would be better if they defaulted to None, let the DB decide
when both are None and when one is not None do the ordering that implies.
--
Ticket URL: <https://code.djangoproject.com/ticket/33543>
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