#django

limbera: why would tou have the same assets on each app?

bah... they left

lindii that was for

wrong person FunkyBob

yup

that's what I get for trusting tab completion :P

hehe

Any suggestions on forcing a JOIN?

jfkdaddy: sorry, back...

joins are handled implicitly

if you do Drink.objects.prefetch_related('ingredients_order') that will do 2 queries -- one for the Drink objects, and one for related ingredient_order records

it then pre-fills the ORM so each Drink will have all its related 'ingredient-order' records already

if you also include select_related('ingredients_order__ingredient') it should follow on and pre-load the related ingredient to each ingredient_order record

Here's the JOIN I'd like to do, but if it ends up being two queries instead of one, that's fine for now. [SELECT cocktail_id, name, `order`, color FROM menus_cocktailingredientorder JOIN menus_ingredient ON menus_ingredient.id = menus_cocktailingredientorder.ingredient_id WHERE cocktail_id IN (...) ORDER BY cocktail_id]. Let me chain those two together and see what happens.

jfkdaddy: FunkyBob's point was that the ORM emits two queries when you use prefetch_related()

Ok, that makes sense and lines up with what I'm seeing.

On the topic of ModelForms: There is a known and specific field that must be conditionally excluded from my form depending on the state of the model instance that was passed into the form's constructor. Perhaps my issue is that I don't understand the relationship between class Meta and the __init__ method? https://dpaste.de/qPTg

So now I'm down to http://i.imgur.com/6GyhfOd.png?1 from http://i.imgur.com/vrmCABw.png?1.

looks like you need the select_related through to ingredient

N1cXP8ChUBFe3: use two form classes

FunkyBob: I was afraid of that

jfkdaddy: that "LIMIT 21" seems wrong... I assume that's your pagination size?

N1cXP8ChUBFe3: why? it's not hard

It does seem odd--my pagination size is either 3 or 10, I forget.

so, how does your query look now? building the queryset, I mean

I'm still trying to interpret your suggestion since adding select_related('ingredient') doesn't seem to help. :)

no

because Drink doesn't have ingredient, does it?

ingredient is a fkey on your IngredientOrder model, right?

cocktailingredientorder

Correct.

so take whatever you put in prefetch_related, and try tacking __ingredient onto it.. pass that to select_related

Ah, but the query is already "drinks.prefetch_related('ordered_ingredients').select_related('ordered_ingredients__ingredient')"

ok

that's why I asked for that

well, try adding it to prefetch_related instead

in 1.7 you should even be able to use a Prefetch to affect the select_related

Boom! That helped a lot. Now I'm down (minus the COUNT(*) query) to one SELECT each for the cocktail, cocktailingredientorder, and ingredient tables.

sweet

the Prefetch might bring that down to 2, instead of 3

but... 3 is still better than N*M*2 :)

FWIW, drinks.prefetch_related('ordered_ingredients__ingredient') seems to get the job done by itself without .select_related('ordered_ingredients__ingredient').

yes, it will

sorry, I wasn't clear about that

No worries at all, dude. You've helped me out a ton.

Thank you!

I think I can get rid of the (seemingly silly) COUNT(*) from Paginator by setting its _count attribute to something high.

FunkyBob: Just seems like there should be a simple way to conditionally blacklist fields of a new ModelForm instance without using factories etc. Calling del self.fields['field_name'] from inside __init__ results in passing the "walks and quacks like a duck" test, and I have similarly appended new fields this way in previous forms. But what are the caveats to calling del self.fields['field_name'] from inside the __init__

method? Does the exclude attribute offer any solutions?

Eh, I remove fields in the constructor all the time..

mattmcc: care to enlighten me? :)

Seems like you already know how to do it.

mattmcc: grr. I guess the exclude attribute was misleading me.

Oh well, I guess that clarifies things... thanks.

I prefer to explicitly include fields on a ModelForm.

schnickel: I do unconditionally whitelist fields via the Meta class, but I use the same form to update previously created objects. One of the attributes of those objects might be read-only so sometimes I have to blacklist the field from the form when its being used modify an existing object.

which is where I would define a common base class, and a sub class with the include fields I want for the Add versus Edit modes

and you can just leave all the per-field clean methods on the base class

true

FunkyBob: Regarding LIMIT 21: http://www.mail-archive.com/django-users@google...

IIRC, there was also a newer discussion about LIMIT 21, too.

ah, ok

So tacking on .prefetch_related(_menu) [drinks = drinks.prefetch_related('ordered_ingredients__ingredient').prefetch_related('menu')] gets me a nice SELECT ... IN for the relevant rows, but when I iterate through drinks, accesses to drink.menu.get().neighborhood aren't cached and yield a ton of SELECTs on the menu table.