#14030: Use F() objects in aggregates(), annotates() and values()
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Reporter: delfick | Owner: nate_b
Type: New feature | Status: assigned
Component: ORM aggregation | Version:
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
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Comment (by nate_b):
The patches posted here are insufficient to effectively solve this
problem.
I have come up with a better solution: refactoring of Aggregate into
ExpressionNode.
I have uploaded my branch; it can be found here:
https://github.com/NateBragg/django/tree/14030
Some particular points of note:
* I tried to preserve as much interface as possible; I didn't know how
much was considered to be more public, so generally I tried to add rather
than subtract. However, I did remove a couple things - if you see
something missing that shouldn't be, let me know.
* Currently, I'm getting the entire test suite passed on sqlite, postgres,
mysql, oracle, and postgis. I was unable to test on oracle spatial - any
help with that would be appreciated.
* When fields are combined, they are coerced to a common type;
IntegerFields are coerced to FloatFields, which are coerced into
DecimalFields as needed. Any other kinds of combinations must be of the
same types. Also, when coerced to a DecimalField, the precision is
limited by the original DecimalField. If this is not correct, or other
coercions should be added, I'd like to correct that.
* When joins are required, they tend to be LEFT OUTER; I'd like some
feedback on this, as I'm not 100% sure its always the best behavior.
* As the aggregates are a little more complicated, on trivial cases there
is a minor reduction in performance; using djangobench, I measured
somewhere between a 3% and 8% increase in runtime.
* I don't have enough tests - mostly for a lack of creativity. What kind
of composed aggregates and expressions would you like to see? I'll add
tests for them.
--
Ticket URL: <https://code.djangoproject.com/ticket/14030#comment:17>
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