CODEWITHSUNDEEP
pythondjango
jvanheijzen
jvanheijzen

Reputation: 349

Lazy querysets in django

This is more of an efficiency question. My django web page is working fine, in the sense that I don't get any errors, but it is very slow. That being said, I don't know where else I would ask this, other than here, so here goes:

I am developing a sales dashboard. In doing so, I am accessing the same data over and over and I would like to speed things up.

For example, one of my metrics is number of opportunities won. This accesses my Opportunities model, sorts out the opportunities won within the last X days and reports it.

Another metric is neglected opportunities. That is, opportunities that are still reported as being worked on, but that there has been no activity on them for Y days. This metric also accesses my Opportunities model.

I read here that querysets are lazy, which, if I understand this concept correctly, would mean that my actual database is accessed only at the very end. Normally this would be an ideal situation, as all of the filters are in place and the queryset only accesses a minimal amount of information.

Currently, I have a separate function for each metric. So, for the examples above, I have compile_won_opportunities and compile_neglected_opportunities. Each function starts with something like:

won_opportunities_query = Opportunities.objects.all()

and then I filter it down from there. If I am reading the documentation correctly, this means that I am accessing the same database many, many times.

There is a noticeable lag when my web page loads. In an attempt to find out what is causing the lag, I commented out different sections of code. When I comment out the code that accesses my database for each function, my web page loads immediately. My initial thought was to access my database in my calling function:

opportunities_query = Opportunities.objects.all()

and then pass that query to each function that uses it. My rationale was that the database would only be accessed one time, but apparently django doesn't work that way, as it made no obvious difference in my page load time. So, after my very long-winded explanation, how can I speed up my page load time?

Upvotes: 1

Views: 8778

Answers (1)

ipaleka
ipaleka

Reputation: 3967

If I am reading the documentation correctly, this means that I am accessing the same database many, many times.

https://pypi.org/project/django-debug-toolbar/

Btw, go with this one https://docs.djangoproject.com/en/2.2/ref/models/querysets/#select-related

Upvotes: 1

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