db_index=True not working, and indexes in class Meta yes

[Gonzalo Amadio]

I have a model like this (simplified code):

class Agreement(modes.Model):
    job = models.ForeignKey(...)
    class Meta:
         indexes = (                        
             models.Index(fields=['job']),
        )

And when run migrations, the index is created.

BUT, after doing this:

class Agreement(modes.Model):
    job = models.ForeignKey(..., db_index=True)

And running makemigrations, I have this on my console output:

- Remove index agreements__job_id_eb7df0_idx from agreement

Why db_index, is not working like it is supposed to work? 

[Jason]

django automatically creates an index for foreign key columns, unless you specify db_index=False for that field.

what I suspect is happening here, you're telling django that it should have two indices for that particular column covering identical areas of responsibility.

[Gonzalo Amadio]

Yes, exactly. Django doc tells they do the same. And they do, but if you do not specify db_index=False in field, both indexes are created.

Here is exaplanation : https://stackoverflow.com/questions/53966256/django-db-index-true-not-creating-index-but-class-meta-indexes-yes