I just found out that orand andare defined for QuerySet. This means that to do queries union or intersection, you can do:
User.objects.filter(...) | User.objects.filter(...)
User.objects.filter(...) & User.objects.filter(...)Subscribe for the news and updates
SQL is a fairly complicated language with a steep learning curve. For a large number of people who make use of SQL, learning to apply it efficiently takes lots of trials and errors. Here are some tips on how you can make your SELECT queries better. The majority of tips should be applicable to any relational database management system, but the terminology and exact namings will be taken from PostgreSQL.
Django ORM is a very abstract and flexible API. But if you do not know exactly how it works, you will likely end up with slow and heavy views, if you have not already. So, this article provides practical solutions to N+1 and high loading time issues. For clarity, I will create a simple view that demonstrates common ORM query problems and shows frequently used practices.
We often handling API server updates including backwards-incompatible changes when upgrading web applications. At the same time we update the client part, therefore, we did not experience any particular difficulties.
There is such a term as Remote Procedure Call (RPC). In other words, by using this technology, programs can call functions on remote computers. There are many ways to implement RPC.
There was a task to submit form with ajax, with server side validation of course. Obvious solution is to do validation and return json with erros. I didn't like idea of writing separate view for validation and then inserting errors in form html on client side. Especially since I already had a generic template for django form with errors display. In this article I'll describe how I solved the task.
In UNIX way, each view should solve single task. This is good idea, but sometimes we need to mix logic of different views on same page. Filter, sort, paginate, or, for example, add comment on product page. In this article I'll show how we can mix such multiple views.