#27719: Add queryset.alias() to mimic .annotate() for aggregations without
loading
data
-------------------------------------+-------------------------------------
Reporter: Marc Tamlyn | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
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 Marc Tamlyn):
Whilst support in all the places which can use an annotated name would
solve this kind of performance problem, there are loads of ways you can
use a field name after it's defined.
`.filter(name__lookup=value)`
`.order_by('name')`
`.annotate(SomeOtherExpression('name'))`
`.values('name')` (and related APIs)`
`.distinct()`
`.date()` (and `datetimes`)
`.defer('name')` (and `only`)
I know that some of these places already support expressions. For very
complex expressions there's utility in being able to "name" the expression
as some kind of virtual field. If you're within the same function then a
python reference is usually sufficient (except for the `__lookup` case),
but if you have for example a manager method which would annotate a
certain field and you use it elsewhere then things get messy quickly.
--
Ticket URL: <https://code.djangoproject.com/ticket/27719#comment:3>
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