Re: Optimizing admin change view with inlines

On 12/23/14 19:13, 'Petros Moisiadis' via Django users wrote:
> Hello people :)
>
> I am struggling with optimizing an admin with inlines which causes too
> many database requests.
>
> My model structure is like this:
>
> class ExampleA(models.Model):
> ...
>
> class ExampleB(models.Model):
> aexample = models.ForeignKey('ExampleA', related_name='bexamples')
> cexample = models.ForeignKey('ExampleC')
> dexample = models.ForeignKey('ExampleD')
> eexample = models.ForeignKey('ExampleE')
> ...
>
> class ExampleC(models.Model):
> ...
>
> class ExampleD(models.Model):
> ...
>
> class ExampleE(models.Model):
> ...
>
> The admin classes:
>
> class ExampleBInline(admin.StackedInline):
> model = ExampleB
> extra = 0
>
> class ExampleAAdmin(admin.ModelAdmin):
> inlines = [ExampleBInline]
>
> admin.site.register(ExampleA, ExampleAAdmin)
>
> As I can see with django-debug-toolbar, when rendering the admin
> template for the inline formset with the forms for ExampleB objects, a
> new db request is sent to db server for each related field of each
> ExampleB object. Particularly, I am seeing a lot of queries like these:
>
> SELECT ••• FROM `examplec` WHERE `examplec`.`id` = 1 LIMIT 21
> SELECT ••• FROM `examplee` WHERE `examplee`.`id` = 2 LIMIT 21
> SELECT ••• FROM `examplec` WHERE `examplec`.`id` = 2 LIMIT 21
> SELECT ••• FROM `exampled` WHERE `exampled`.`id` = 2 LIMIT 21
> SELECT ••• FROM `examplee` WHERE `examplee`.`id` = 3 LIMIT 21
>
> The template context is this (I am using grappelli):
>
> 21 {% if field.is_readonly %}
> 22 <div class="grp-readonly">{{
> field.contents|linebreaksbr }}</div>
> 23 {% else %}
> the marked line => 24 {{ field.field }}
> 25 {% endif %}
> 26 {% endif %}
> 27 {% if line.fields|length_is:'1' %}{{
> line.errors }}{% endif %}
>
>
> I have tried the following optimizations:
>
> First try:
>
> class ExampleAAdmin(admin.ModelAdmin):
> inlines = [ExampleBInline]
>
> def get_queryset(self, request):
> qs = super(ExampleAAdmin, self).get_queryset(request)
> return qs.prefetch_related('bexamples',
> 'bexamples__cexample', 'bexamples__dexample', 'bexamples__example')
>
> Second try:
>
> class ExampleBInline(admin.StackedInline):
> model = ExampleB
> extra = 0
>
> def get_queryset(self, request):
> qs = super(ExampleInline, self).get_queryset(request)
> return qs.select_related('cexample', 'dexample', 'eexample')
>
> Third try:
>
> class BaseExampleBFormSet(BaseInlineFormSet):
> def __init__(self, *args, **kwargs):
> super(BaseExampleBFormSet, self).__init__(*args, **kwargs)
> qs = self.queryset
> self.queryset = qs.select_related('cexample', 'dexample',
> 'eexample')
>
> ExampleBFormSet = inlineformset_factory(ExampleA, ExampleB,
> formset=BaseExampleBFormSet)
>
> class ExampleBInline(admin.StackedInline):
> model = ExampleB
> extra = 0
> formset = ExampleBFormSet
>
> Unfortunately, none of the above works.
>
> So, I would be really grateful if anyone could help on this by giving
> any hint or pointing out what could be possibly missing. Or, could I
> have hit a restriction of django admin's internals?
>
> Thank you in advance,
>
> Petros
>

Hello again,

I would like to clarify that the big number of db requests is not caused
by fetching all the objects for the related model to populace select
boxes for the related fields in the line, as it is often the case. To
avoid that, I have included the related fields in raw_id_fields. I have
also used grappelli's convenient autocomplete lookup feature, but that
does not add extra queries. So, the inline class actually looks like this:

class ExampleBInline(admin.StackedInline):
model = ExampleB
extra = 0
raw_id_fields = ['cexample', 'dexample', 'eexample']
autocomplete_lookup_fields = {
'fk': ['cexample', 'dexample', 'example'],
}

The only optimization that works is adding the related fields in
readonly_fields in combination with a queryset changing method with
select_related(), like this:

class ExampleBInline(admin.StackedInline):
model = ExampleB
extra = 0
raw_id_fields = ['cexample', 'dexample', 'eexample']
autocomplete_lookup_fields = {
'fk': ['cexample', 'dexample', 'eexample'],
}
readonly_fields = ['cexample', 'dexample', 'eexample']

def get_queryset(self, request):
qs = super(ExampleBInline, self).get_queryset(request)
return qs.select_related('cexample', 'dexample', 'eexample')


However, I am not satisfied with that solution because I do want to be
able to edit the related fields inline.

--
You received this message because you are subscribed to the Google Groups "Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscribe@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users.
To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/549AA3ED.10309%40yahoo.gr.
For more options, visit https://groups.google.com/d/optout.