A generic cache decorator around low level cache api

[suayip uzulmez]

Usually, I need to construct a simple cache pipeline to optimize database access using low-level cache API (django.core.cache).

I think we could use a decorator as such to ease this process:

cached_context(key, *, timeout, cache)

I know higher-level utilities exist such as cache_page, however I think the decorator above provides more granularity over what to cache. For example, I usually need such decorator in model methods where I do some database aggregation operations based on the instance.

What do you think?

[Adam Johnson]

I'm not sure I quite understand your proposal. Are you suggesting a decorator that caches the results of every queryset that is resolved within the decorated function?

If so, I'm not sure how useful it would be. First, if a single query is problematic, there’s normally a way to optimize it within the database - for example, a materialized view allows you to “cache” query results and recompute them in the background. Second, QuerySets are lazy, so it could be surprising to decorate a function that returns a QuerySet that is not yet resolved.

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[suayip uzulmez]

It doesn't necessarily have to be a QuerySet; any function or  method that takes some processing time could be decorated (e.g., an external call to an API). My aim is to reduce this code:

def do_some_processing():
    cache_key = "key"

    if cached_value := cache.get(cache_key):
        return cached_value

    fresh_value = do_some_computing()
    cache.set(cached_value, fresh_value, 30)
    return fresh_value

to this:

@cached_context("key", timeout=30)
def do_some_processing():
    return do_some_computing()

AFAIK cache.set evaluates QuerySets, how would that be a problem?.

26 Ağustos 2022 Cuma tarihinde saat 12:24:39 UTC+3 itibarıyla Adam Johnson şunları yazdı:

[suayip uzulmez]

I would like to see more opinions on this, I am using this type of utility in almost every project I make and it seems to me it would a decent utility function.

26 Ağustos 2022 Cuma tarihinde saat 14:45:13 UTC+3 itibarıyla suayip uzulmez şunları yazdı:

[Diederik van der Boor]

You’d mean something like this (for inspiration)?

https://gist.github.com/vdboor/80e5ffa148fb30d33d938593855af9ac

This would give the simplicity of using a @cache_results decorator,

while allowing to bypass or refresh the cache when needed.

I’m not sure but likely there are some packages that have a similar function.

Best,

Diederik

To view this discussion on the web visit https://groups.google.com/d/msgid/django-developers/df61bbf0-e0b3-41aa-beba-d343fe6685a6n%40googlegroups.com.

[suayip uzulmez]

Yes something like this. I would comment on implementation details, but at this point I want to know if people would be content to add this sort of functionality to core.

Of course, there bound to be a library that essentially does this, however seeing it as such a common utility I think it would be great to have it in core and not bother with a 3rd party library.

4 Ocak 2023 Çarşamba tarihinde saat 20:06:28 UTC+3 itibarıyla Diederik van der Boor şunları yazdı: