#30317: model_to_dict() makes separate db calls for each missing field
-------------------------------------+-------------------------------------
Reporter: Chris Hranj | Owner: nobody
Type: | Status: closed
Cleanup/optimization |
Component: Forms | Version: master
Severity: Normal | Resolution: wontfix
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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Changes (by Carlton Gibson):
* status: new => closed
* resolution: => wontfix
Comment:
Hi Chris.
Thanks for the report. (Unless you have an unforeseen concrete proposal in
mind) I think we have to say `wontfix` here.
`model_to_dict` is just using the field properties. It has no knowledge of
whether they deferred or not. (And that's not something we'd add there.)
So, you really need to be passing in objects that already have the
required fields loaded. That you're not doing this suggests you're over-
using `only() here. See again the warning note:
> The defer() method (and its cousin, only(), below) are only for advanced
use-cases. They provide an optimization for when you have analyzed your
queries closely and understand exactly what information you need and have
measured that the difference between returning the fields you need and the
full set of fields for the model will be significant.
If you're sure you're using `only()` correctly, your best bet is probably
to add a `defer(None)` and re-fetch once before running through
`model_to_dict()`.
--
Ticket URL: <https://code.djangoproject.com/ticket/30317#comment:1>
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