#31295: Avoid Select widget triggering additional query when using
ModelChoiceIterator.
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Reporter: Aurélien Pardon | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: Forms | Version: 2.2
Severity: Normal | Resolution:
Keywords: Model | 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 Aurélien Pardon):
Hi Carlton,
Thanks for your answer. I'm afraid the code you proposed won't work, I
just tested it. I will try to think about a solution.
The difficulty is that when rendering the widget, we need '''before
rendering the options''' (and thus iterate over the
ModelChoiceFieldIterator/fetch the data from the DB) if the HTML attribute
{{{required}}} should be used.
And we also don't want to cache the query, for memory usage performance.
I think of two different solutions :
* defer the presence of the {{{required}}} attribute after the iteration
for the <options>. During this iteration, we store the fact that the first
option allows or not the {{{required}}} attribute. After the rendering of
the options, we put afterwards (or not) the {{{required}}} attribute.
Maybe with a placeholder replaced by a regexp? I find this quite ugly.
* Maybe the ModelChoiceIterator may cache it's first value? It should
not take a lot of memory. I don't think it will work because I assume
that, for efficiency, multiple rows are fetched from the database, if you
want to cache the first value for an ulterior iteration, you also have to
cache the rest of the rows until <options> are iterated.
--
Ticket URL: <https://code.djangoproject.com/ticket/31295#comment:13>
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