#34699: Filtering on annotated TruncSecond expression gives unexpected result.
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Reporter: Stefan | Owner: Francesco
Type: | Panico
Cleanup/optimization | Status: assigned
Component: Database layer | Version: 4.2
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Natalia Bidart):
Replying to [comment:9 Mariusz Felisiak]:
> It works as documented:
> - `timezone.now()` - ''"If USE_TZ is True, this will be an aware
datetime representing the **current time in UTC**. Note that now() will
always return times in UTC regardless of the value of TIME_ZONE; you can
use localtime() to get the time in the current time zone."''
> - `Trunc()` - ''"If a different timezone like Australia/Melbourne is
active in Django, then the datetime **is converted to the new timezone**
before the value is truncated."''
Right, I understand the docs above and how that match the results I got.
But, at the same time, the first paragraph about "Time Zones" says:
''When support for time zones is enabled, Django stores datetime
information in UTC in the database, uses time-zone-aware datetime objects
internally, and translates them to the end user’s time zone in templates
and forms.
[...]
Even if your website is available in only one time zone, it’s still good
practice to store data in UTC in your database.''
The above aligns perfectly (and makes sense) with `timezone.now` returning
an aware datetime in UTC. But then, at least to me, is quite surprising
that `TruncSecond`, which is an operation fully occurring in the DB, would
not "respect" that "UTC invariant" and have the `TIME_ZONE` setting
affecting the results. Does my point make sense? Do you have historic
information about why `TruncSecond` (and related functions) would not
operate with/keep the tz defined in the datetime being processed?
--
Ticket URL: <https://code.djangoproject.com/ticket/34699#comment:10>
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