How to index just selected json key using Django functionality instead of all keys?

Question

I have the next model:

from django.contrib.postgres.fields import JSONField
from django.contrib.postgres.fields.jsonb import KeyTextTransform
from django.contrib.postgres.indexes import GinIndex
from django.contrib.postgres.search import SearchVectorField, SearchVector
from django.db import models


class ProfileUser(models.Model):
    name = JSONField()
    search_vector = SearchVectorField(null=True)

    class Meta:
        indexes = [GinIndex(fields=["search_vector"], name="user_full_name_gin_idx")]

    def save(self, *args, **kwargs):
        super(ProfileUser, self).save(*args, **kwargs)
        ProfileUser.objects.filter(pk=self.pk).update(search_vector=SearchVector('name'))

        # I have tried this, but this does not work.
        # ProfileUser.objects.filter(pk=self.pk).update(search_vector=SearchVector(KeyTextTransform('name', 'name')))

And name looks like [{'name': 'Random Name', 'lang': 'en'}, {'name': 'Какое-то Имя', 'lang': 'ru'}].

Currently the code above indexes both name and lang keys. Is it possible using Django to index just name key? I found how to workaround this using SQL directly, but I just want to know, if it is possible to do that just via Django.

I use Django 2.2 and PostgreSQL 12.

Answer 1

Functional indexes is going to be available in Django 3.2 in April. This finally should allow to build needed indexes from Django.