Re: [Django] #31582: Django template engine render pre-fetches data even when iterator() is used
#31582: Django template engine render pre-fetches data even when iterator() is used -+-- Reporter: Sümer Cip|Owner: nobody Type: New feature | Status: closed Component: Template system | Version: 3.0 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 -+-- Changes (by Carlton Gibson): * stage: Accepted => Unreviewed -- Ticket URL: <https://code.djangoproject.com/ticket/31582#comment:12> Django <https://code.djangoproject.com/> The Web framework for perfectionists with deadlines. -- You received this message because you are subscribed to the Google Groups "Django updates" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-updates+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-updates/064.b8bc3c6ba6eb1e44ae5ce64755b9487f%40djangoproject.com.
Re: [Django] #31582: Django template engine render pre-fetches data even when iterator() is used
#31582: Django template engine render pre-fetches data even when iterator() is used -+ Reporter: Sümer Cip|Owner: nobody Type: New feature | Status: closed Component: Template system | Version: 3.0 Severity: Normal | Resolution: wontfix Keywords: | Triage Stage: Accepted Has patch: 0| Needs documentation: 0 Needs tests: 0| Patch needs improvement: 0 Easy pickings: 0|UI/UX: 0 -+ Changes (by Carlton Gibson): * status: new => closed * resolution: => wontfix Comment: > I certainly don't think adding another argument is a good idea, because you could then end up with something absurd like... OK. I think Keryn's analysis is correct. I agree the extra param doesn't look nice, but I can't see another way. So short of a concrete proposal, I think we have to say `wontfix`. (Happy to reopen if an acceptable proposal is forthcoming.) -- Ticket URL: <https://code.djangoproject.com/ticket/31582#comment:11> Django <https://code.djangoproject.com/> The Web framework for perfectionists with deadlines. -- You received this message because you are subscribed to the Google Groups "Django updates" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-updates+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-updates/064.9f9c129881d826595707a17f9cb7dc6e%40djangoproject.com.
Re: [Django] #31582: Django template engine render pre-fetches data even when iterator() is used
#31582: Django template engine render pre-fetches data even when iterator() is
used
-+
Reporter: Sümer Cip|Owner: nobody
Type: New feature | Status: new
Component: Template system | Version: 3.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0| Needs documentation: 0
Needs tests: 0| Patch needs improvement: 0
Easy pickings: 0|UI/UX: 0
-+
Comment (by Keryn Knight):
Yielding for all rendering rather than build up the `nodelist` would
presumably assist in fixing the problem, but the problem itself would
still have to remain as long as `revcounter` and `revcounter0` are
documented as being there (I've no idea who'd use those, but presumably
they exist for a reason). For `last` you can probably rework the loop to
be based around using `next(...)` to find out if there *is* another item
to yield, if there's not. That's last. Similarly for empty nodes rendering
you can check whether the first `next()` raised `StopIteration`
But until `revcounter` and `revcounter0` become optional (ie: the
guarantee is only made if the `items` has a `__len__`) you can't avoid
consuming the iterator to find out the overall span. I certainly don't
think adding another argument is a good idea, because you could then end
up with something absurd like `{% for x in mymodel.objects.all.iterator
iterator %}` or `{% for x in mymodel.objects.all iterator %}`, right?
which both look like typos or accidents.
I don't know if the exception made by doing
`reversed(mymodel.objects.all().iterator())` would get swallowed by DTL or
surfaced, but that'd be another consideration. If it's surfaced I think
that's fine, if it's not that's ''another'' issue.
--
Ticket URL: <https://code.djangoproject.com/ticket/31582#comment:10>
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Re: [Django] #31582: Django template engine render pre-fetches data even when iterator() is used
#31582: Django template engine render pre-fetches data even when iterator() is used -+ Reporter: Sümer Cip|Owner: nobody Type: New feature | Status: new Component: Template system | Version: 3.0 Severity: Normal | Resolution: Keywords: | Triage Stage: Accepted Has patch: 0| Needs documentation: 0 Needs tests: 0| Patch needs improvement: 0 Easy pickings: 0|UI/UX: 0 -+ Comment (by Carlton Gibson): Ah, I didn't properly read this bit: > context is pointing to the item which is the model itself! Even we fix above len() call somehow, this will hurt us again. There's an effort to allow a generator based approach to template rendering in #13910. There's a PR for that which got so far but needs pushing over the line. I don't know if that would solve second issues here...? -- Ticket URL: <https://code.djangoproject.com/ticket/31582#comment:9> Django <https://code.djangoproject.com/> The Web framework for perfectionists with deadlines. -- You received this message because you are subscribed to the Google Groups "Django updates" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-updates+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-updates/064.82b713cab0f04026e86ce2bfc1a51c5b%40djangoproject.com.
Re: [Django] #31582: Django template engine render pre-fetches data even when iterator() is used
#31582: Django template engine render pre-fetches data even when iterator() is
used
-+
Reporter: Sümer Cip|Owner: nobody
Type: New feature | Status: new
Component: Template system | Version: 3.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0| Needs documentation: 0
Needs tests: 0| Patch needs improvement: 0
Easy pickings: 0|UI/UX: 0
-+
Changes (by Carlton Gibson):
* type: Bug => New feature
* stage: Unreviewed => Accepted
Comment:
Good follow up both, that's super!
At first glance, certainly :), consuming the iterator into a list isn't
ideal.
Question is, what can we do about it?
The next line is:
{{{
len_values = len(values)
}}}
Then `len_values` is used to populate the various loop counter variables.
`revcounter`, `last` and so on.
I haven't thought it through but, I could see these possibly being made
optional, maybe along the lines of adding an extra option like `reversed`?
(It would require editing the `do_for()` function to parse another option.
Not sure what it should be: ...`iterator`? )
I think we'd have to call that a new feature. The behaviour isn't
**incorrect**, it just uses more memory than we'd like in this case.
Let's provisionally accept on that basis. It might be worth pinging the
DevelopersMailingList to seek advice on how to proceed, particularly with
regard to the possible API for such a change.
--
Ticket URL: <https://code.djangoproject.com/ticket/31582#comment:8>
Django <https://code.djangoproject.com/>
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Re: [Django] #31582: Django template engine render pre-fetches data even when iterator() is used (was: Django template backend allocates model cache even iterator() is used)
#31582: Django template engine render pre-fetches data even when iterator() is used -+-- Reporter: Sümer Cip|Owner: nobody Type: Bug | Status: new Component: Template system | Version: 3.0 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 -+-- -- Ticket URL: <https://code.djangoproject.com/ticket/31582#comment:7> Django <https://code.djangoproject.com/> The Web framework for perfectionists with deadlines. -- You received this message because you are subscribed to the Google Groups "Django updates" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-updates+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-updates/064.6ab922693347aa4c11b61662ce37ae7d%40djangoproject.com.
