Auto increment doesn't work on primary key

Using Django
1

Hi,

I have a model called ObjetArchi.
The primary key field looks like this:

id_objet_archi = models.AutoField(primary_key=True)

As for my previous messages, I’m working on a legacy database. The primary key field already existed, hence the custom name.
When I try to add a new object through the admin form, the auto increment doesn’t seem to work and the following error appears:

null value in column “id_objet_archi” of relation “objetarchi” violates not-null constraint

I first set id_objet_archi as an IntegerField but the auto increment didn’t work either, so I was looking for the appropriate type.

Here is admin.py:

from django.contrib.gis import admin
from django.contrib.gis.geos import Point
from .models import Illustrations, Materiau, ObjetArchi, Pays, ProvinceAntique, Region, Ville, Monument, CiteAntique, SiteAntique, Ensemble
class IllustrationsAdmin(admin.ModelAdmin):
    search_fields = ('legende', 'lien')

class IllusInline(admin.TabularInline):
    model = Illustrations
    fields = ('images', 'legende', 'principale')  

class ObjetArchiAdmin(admin.OSMGeoAdmin):
    list_display = ('titre', 'date')
    search_fields = (
        'titre',
        'prov_pays__nom',
        'prov_region__nom',
        'prov_departement__nom',
        'prov_ville__nom', 
        'cons_pays__nom', 
        'cons_region__nom', 
        'cons_departement__nom', 
        'cons_ville__nom', 
        'materiau__nom'
    )
    autocomplete_fields = ('prov_pays', 'prov_region', 'prov_departement','prov_ville', 'cons_pays', 'cons_region', 'cons_departement', 'cons_ville', 'materiau', 'ensemble', 'provinceantique', 'siteantique', 'citeantique', 'monument')
    exclude = ('id_objet_archi','lien_pdf', 'reference', 'version', 'observations', 'ref_repro', 'issn_objetarchi', 'flag_soumission_comite', 'lat', 'lon', 'cons_lieu', 'flag_del_objetarchi')
    inlines = (
        IllusInline,
    )
    pnt = Point(5.855572,47.019214, srid=4326)
    pnt.transform(900913)
    default_lon, default_lat = pnt.coords

class PaysAdmin(admin.ModelAdmin):
    search_fields = ['nom']

class RegionAdmin(admin.ModelAdmin):
    search_fields = ['nom']

class DepartementAdmin(admin.ModelAdmin):
    search_fields = ['nom']

class VilleAdmin(admin.ModelAdmin):
    search_fields = ['nom']

class PAntiqueAdmin(admin.ModelAdmin):
    search_fields = ['nom']   

class SAntique(admin.ModelAdmin):
    search_fields = ['nom']

class CAntique(admin.ModelAdmin):
    search_fields = ['nom']

class MateriauAdmin(admin.ModelAdmin):
    search_fields = ['nom']

class EnsembleAdmin(admin.ModelAdmin):
    search_fields = ['nom']

class MonumentAdmin(admin.ModelAdmin):
    search_fields = ['nom']

admin.site.register(ObjetArchi, ObjetArchiAdmin)
admin.site.register(ProvinceAntique, PAntiqueAdmin) 
admin.site.register(CiteAntique, CAntique)
admin.site.register(SiteAntique, SAntique) 
admin.site.register(Pays, PaysAdmin) 
admin.site.register(Region, RegionAdmin)
admin.site.register(Departement, DepartementAdmin) 
admin.site.register(Ville, VilleAdmin) 
admin.site.register(Monument, MonumentAdmin)
admin.site.register(Materiau, MateriauAdmin) 
admin.site.registr(Ensemble, EnsembleAdmin) 
admin.site.register(Illustrations, IllustrationsAdmin)

Is there something obviously wrong that I missed?

Thanks for your help!