How to run a filter over the property of my Django Model?

I am working with a Model has a payload property which contains a Base64 encoded JSON. I am writing admin views which will consolidate data represented by this m开发者_运维知识库odel and several others.

1. I want to display the Base64 decoded version of the JSON in ModelAdmin views.
2. I also want to run a query which would return rows such that a specific element in the decoded JSON matches a value.

Is this doable in Django ?

You have to create a custom admin template with the following code:

{% extends "admin/change_form.html" %}
{% load i18n %}

{% block content %}
    This is the field: {{ original.payload }}
    {{ block.super }}
{% endblock %}

save it as, say, "templates/admin/change_model_payload.html" and add this to the model's ModelAdmin:

change_form_template = "admin/change_model_payload.html"

For #2, you might want to create a custom template tag to retrive the DB entries.

If you expect a specific element of a specific type, then you'd better decode it on save() than to blindly store it in base64.

1. There is no easy way to get info from base64-encoded data.
2. base64 does not align on bytes boundaries, so you can't look at the encoded data and say "ah, there starts the property xxx!"
3. json should already have its binary data encoded in base64, so you shouldn't encode it again in base64.

My advice is to create a PayloadData class with all the expected attributes, with a one-to-one to your original model, where you store the attributes upon save()ing the payload, and where you can index, query, filter, order, join and any other interesting things a RDBMS allows you to do.

OR ditch you database and Django's own ORM and go no-sql. Most document-based nosql servers have the ability to query (or at least create views) for any kind of subfield condition.