CODEWITHSUNDEEP
pythonmysqldjangomultithreadingdjango-models
slacy
slacy

Reputation: 11763

Are asynchronous Django model queries possible?

I'm new to Django, but the application that I have in mind might end up having URLs that look like this:

http://mysite/compare/id_1/id_2

Where "id_1" and "id_2" are identifiers of two distinct Model objects. In the handler for "compare" I'd like to asynchronously, and in parallel, query and retrieve objects id_1 and id_2.

Is there any way to do this using a standard Django syntax? I'm hoping for pseudocode that ends up looking something like this: 

import django.async 

# Issue the model query, but set it up asynchronously.  
# The next 2 lines don't actually touch my database 
o1 = Object(id=id_1).async_fetch()
o2 = Object(id=id_2).async_fetch()

# Now that I know what I want to query, fire off a fetch to do them all
# in parallel, and wait for all queries to finish before proceeding. 

async.Execute((o2,o2))

# Now the code can use data from o1 and o2 below...

Upvotes: 23

Views: 6832

Answers (1)

Jarret Hardie
Jarret Hardie

Reputation: 97892

There aren't strictly asynchronous operations as you've described, but I think you can achieve the same effect by using django's in_bulk query operator, which takes a list of ids to query.

Something like this for the urls.py:

urlpatterns = patterns('',
    (r'^compare/(\d+)/(\d+)/$', 'my.compareview'),
)

And this for the view:

def compareview(request, id1, id2):
    # in_bulk returns a dict: { obj_id1: <MyModel instance>, 
    #                           obj_id2: <MyModel instance> }
    # the SQL pulls all at once, rather than sequentially... arguably
    # better than async as it pulls in one DB hit, rather than two
    # happening at the same time
    comparables = MyModel.objects.in_bulk([id1, id2])
    o1, o2 = (comparables.get(id1), comparables.get(id2))

Upvotes: 11

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