#django

Oh, case-when, I was thinking Where()... which is WhereNode(), anyway I think.

Ignore me.

I'd think When(foo__bar=baz) should work.

http://stackoverflow.com/questions/4620385/djan... is exactly what I was looking for

how to make django-template cache refresh initiatively

initiatively?

I don’t want to the first user access website feel slowly

period refresh

one of these days you my actually persuade me you need caching

but every time I try to find out... you stop answering

You mean you want the cache warmed? Can you give some examples of the stuff that needs to be in the cache, and why it can't just be lazily done?

Can someone give me example link for the cascade select app ?

schinckel: SimpleName needs to display 20 products on their front page

sridar: did you check djangopackages?

- - ! I am so sorry @funkybob

Oh, this was the 100000 queries for 20 objects?

schinckel: seems so

turns out it was 100000 products, and only showing 20 of

Hold on, let me check it again and confirm

but more details we never got

sridar: it's called Smart Selects

mikea: is it?

mikea: why did you look up SO, btw, when what you needed was in the docs I linked to?

I tried smart selects but cascading option is not working and I have reported this as issue with another user in their issue list

unless I misunderstood the question

FunkyBob, I was having a difficult time maping what you linked into annotations

sridar, did you setup their urls.py stuff?

yes I did

it works for the type of method that they mentioned as example

but not with my scenario

ah, k

FunkyBob, you got me 80% of the way there. It gave me the info I needed to search for the right answer on my own

yeah, but SO. man.... don't encourage them

heh

I need to caculate top 20 of 100000, by a hot algorithm

and the algorithm is complex

I know I can caculate the result every time , when score of every product update, but the truth, the project is not I write, I just update it,

SimpleName: you have me 50% convinced that you need caching; if your algorithm needs to look at 100000 products, you still need to look into optimizing the algorithm

of course, but there is a question that: the project is not I write it, now I just update it to make it faster

SimpleName: do you have celery?

SimpleName: or anything like that?

of course, I use celery to refresh cache period

: )

i use CELERYBEAT_SCHEDULE

then just run the algorithm every 10 minutes and set is_on_home_page=True on those projects

*products

then filter the home page by is_on_home_page=True

no caching needed

but not only query the result, and I need handle the result , for example, I need to get the field content of every queryset

generate a json data to client

SimpleName: for only 20 objects, it will be fast

in fact, 1000 online user access it at same time

SimpleName: my question remains -- what actual efforts have you done to optimise this calculation?

your method is good, but I think the result cached just only one minute, but it can reduce my server press

SimpleName: the standard django caching will not solve your problem _at least_ because the first user will have to wait

of course, so I have to use celery period task

to solve it

so, what is - currently - the result of the task?

HTML markup? JSON?

if you want to be smarter than caching... you can look at pre-emptive generation

^^ this

do you know what events will cause the data to become stale?

"a second passed"

(guessing)

I would do pre-emptive generation and stick it in something like redis or memcache

json

SimpleName: so what are you loading on the front page?

SimpleName: in fact, _why_ is the front page slow?

you can use memcache or redis outside of the django caching framework if it's just that one piece of data that needs to be cached

not slow, only the first user slow

SimpleName: for the first user, why is it slow?

Koterpillar: this is what I've been trying to get out of SimpleName for the last week of two

of course, I use redis cache django template

FunkyBob: I saw one iteration

- - !

SimpleName: stop talking about the cache... start telling us about what needst to happen to generate the cache value

explain why _that_ is slow,

SimpleName: imagine that you removed the cache tag

SimpleName: it's going to be slow for everyone now, but why?

BECAUSE I'M NOT CACHING

heh

no, just first user have to wait for it , just 3 second

other people is very fast

SimpleName: you're not listening

What does the process do that takes 3 seconds?

SimpleName: when calculating the value to put in the cache.... why does it take so long?

what work is it doing?

Yeah. Pretend that there is no caching.

what have you done to make it faster? what have you done to understand why it is slow?

because the old staff use a complex algorythm

because caching is NOT a good solution

I can ’t use new way

why not?

select * from table; for each result in results: i += 1

lol

- - !

What is it about the old algorithm that makes it slow?

what the fuck is this "- - ! " supposed to mean, SimpleName ?

What is it about the problem that means you can't use a new algorithm?

_ - ! mean awkard

SimpleName: we're tryign to help you fix the problem... but every time we try, you stop us.

My company dont let me use new algorithm

no

What I think he's saying is that he's not allowed to change the algorithm

yes

so implement the algorithm better

of course, If I have chance, I will change it

as I asked you every other time... how many DB queries does it make per Product?

it could be you could make this all a LOT faster by using prefetch_related and/or select_related

but you never answer my question... so ... we don't know

at least, there is 50, 000 to use the complex algorithm to generate the month top’s product

SimpleName: PER PRODUCT

SimpleName: your goal is NOT to run this algorithm in the template

SimpleName: to generate details for a SINGLE PRODUCT... _how_ many DB queries?

yes

50,000 DB queries PER PRODUCT???

I just use 5 of 50, 000

lol

use 5 what of 50,000?

Do you understand the difference between a row and a query?

product

SimpleName: no... I'm asking about a _single_ product