A little background. I've been developing the core code of an application in python, and now I want to implement it as a website for the user, so I've been learning Django and have come across a problem and not sure where to go with it. I also have little experience dealing with databases
Each user would be able to populate their own list, each with the same attributes. What seems to be the solution is to create a single model defining the attributes etc..., and then the user save records to this, and at the same time very frequently changing the values of the attributes of the records they have added (maybe every 5~10 seconds or so), using filters to filter down to their user ID. Each user would add on average 4000 records to this model, so say just for 1000 users, this table would have 4 million rows, 10,000 users we get 40million rows. To me this seems it would impact the speed of content delivery a lot?
To me a faster solution would be to define the model, and then for each user to have their own instance of this table of 4000ish records. From what I'm learning this would use more memory and disk-space, but I'd rather get a faster user experience as my primary end point.
Is it just my thinking because I don't have experience with databases? Or are my concerns warranted and I should find a solution as to how to be able to do the latter?
This post asked the same question I believe, but no solution on how to achieve it. How to create one Model (table) for each user on django?
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I am looking for suggestions on how to deal with a database table that has 1000 or more columns and I am tying to translate it into one or many Django models. The data also needs to be filtered through API calls within the URL. Every field needs to be able to filter the rest of the data.
I have come up with a few solutions and would like input or resources related to them:
Just have a model with 1000+ fields - This seems like it would be a nightmare to maintain and would require a lot of brute force coding but would likely work fine if data was selectively returned.
Use a JSON field to store all less frequently accessed data - The issue here would be difficulty in filtering the data using Django Filters.
Split data into related models connected by One-to-One relationships, as I understand this cuts down on join operations. - This would seem to require more coding than the first option but would be more maintainable.
Does anyone have any information or resources on dealing with database tables of this size?
You should absolutely split the model into multiple linked models.
Because of how Django models data in the database you should generally have a 1:1 relationship between models and tables, and your tables should be normalized to at least the third normal form.
The following image shows a rough draft of my proposed database structure that I will develop for Django. Briefly, I have a list of ocean Buoys which have children tables of their forecast conditions and observed conditions. I'd like Users to be able to make a log of their surf sessions (surfLogs table) in which they input their location, time of surf session, and their own rating.
I'd like the program to then look in the buoysConditions table for the buoy nearest the user's logged location and time and append to the surfLog table the relevant buoyConditions. This will allow the user to keep track of what conditions work best for them (and also eventually create notifications for the user automatically).
I don't know what the name for this process of joining the tables is, so I'm having some trouble finding documentation on it. I think in SQL it's termed a join or update. How is this accomplished with Django?
Thanks!
I'm a beginner at Django, and as a practice project I would like to create a webpage with a dashboard to track investments in a particular p2p platform. They do not have a nice dashboard (but provide excel file with all data). As I see it, main steps that I need to do in this project are as follow:
Create login so that users would have account where they upload their excel files.
Make it possible to import excel file to a database
Manipulate/calculate data for it to be later used in dashboard
Create dashboard.
Host webpage.
After some struggle I have implemented point no. 2, and will deal with 1 and 5 later. But number 3 is my biggest issue now.
I'm completely unsure what I need to do, and google did not help. I need to calculate data before I can make dashboard from it. Union two of the tables, and then join them together with a third table, creating some additional needed calculated fields. Do I create a view in the database and somehow fetch this data to Django? Or do I need to create some rules so that new table would be created at the time of the import? I think having table instead of a view would have better performance. Or maybe I'm doing it completely wrong, and should take completely different approach for this kind of task? Also, is SQLite a good database for a task (I'm using it, because it was a default in Django)?
I assume for vizualization part I will need to do it with some JavaScript library, such as D3? Which then would use data from step 3.
For part 3 there is 2 way, either do these stuff and save the result in your database or you can do it when you need it using django model features like annotation, aggregation and etc.
Option 1 requires to add a table for you calculation which is Models in django.
Option 2 requires to create a doing the annotations in a view or model managers and then using them in views.
Django docs: Aggregation
Which is the best is depended on how big your data is, how complicated the calculation is and how often you need them.
And for database; SQLite is just a database for development use not the production and surly not with a lot of data and a lot of calculations. The recommended database for django is postgresql which is pretty good at handling millions and even billions of data and doing heavy calculation.
And for vizualization you should handle it on the template side which is basically HTML, CSS and JS.
I have a project that looks like a simple shopping site that sells different kinds of products. For example, I have 4 models: Brand, Product, Consignment. Consignment is linked to Product, and Product is linked to Brand. To reduce count of queries to databases, I want to save current state of these models(or at least some of them). I want to do it, because I show a sidebar with brands and products. So every time when user opens some page, it will execute the query to database to get those brands and products.
But when admin add some new product or brand, I want to handle database changing and resave it. How to implement it?
Your answer is by using Cache. Cache is a method to store your objects in memory/other app like redis temporarily so that you do not need send queries to database. You can read the full description here.
Or, you can use this third party library that helps you to cache Django ORM Model. Here are the example.
Brand.objects.filter(name='stackoverlow').cache()
After doing an update to the model, you need to clear or invalidate the cache.
invalidate_model(Brand)
This looks like it should be easy but I just can't find it.
I'm creating an application where I want to give admin site access to people from different departments. Those people will read and write the same tables, BUT they must only access rows belonging to their department! I.e. they must not see any records produced by the other departments and should be able to modify only the records from their own department. If they create a record, it should automatically "belong" to the department of the user which created it (they will create records only from the admin site).
I've found django-guardian, but it looks like an overkill - I don't really want to have arbitrary per-record permissions.
Also, the number of records will potentially be large, so any kind of front-end permission checking on a per-record basis is not suitable - it must be done by DB-side filtering. Other than that, I'm not really particular how it will be done. E.g. I'm perfectly fine with mapping departments to auth groups.