#14030: Use F() objects in aggregates(), annotates() and values()
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Reporter: delfick | Owner: nate_b
Type: New feature | Status: assigned
Component: Database layer | Version:
(models, ORM) | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: aggregate, annotate | Needs documentation: 1
Has patch: 1 | Patch needs improvement: 1
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
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Changes (by smeatonj):
* needs_docs: 0 => 1
Comment:
I've made an attempt at refactoring Aggregates into ExpressionNode as
nateb originally did. The points brought up by @akaariai were mostly
addressed:
- The biggest problem is in the existing F() <-> SQLEvaluator interaction
Addressed by removing the SQLEvaluator structure, and allowing the
Expression to evaluate itself. Backends can customise the sql generation
using the as_{vendor} approach, introduced in the latest lookups refactor.
- the result type coersion in sql/expressions.py feels scary
Addressed by introducing an `output_type` param, which is required for
mixed-type expressions.
Discussion on this particular attempt is on the mailing list:
https://groups.google.com/forum/#!topic/django-developers/8vEAwSwJGMc
The incomplete pull request is: https://github.com/django/django/pull/2184
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Ticket URL: <https://code.djangoproject.com/ticket/14030#comment:31>
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