Search by foreign key id in admin

Question

I'm trying to achieve something apparently simple but I couldn't find any answer, neither on Google nor here. I have a Django model, something dead-simple:

class Shipment(models.Model):
    id = models.AutoField(primary_key=True)
    transaction = models.ForeignKey(Transaction)

I would like to be able to search in my Shipment Admin page by transaction.id. To clarity, I want this (this code obviously doesn't work):

class ShipmentAdmin(admin.ModelAdmin):
    list_display = ('id', 'transaction')
    search_fields = ['id', 'transaction.id']

This can't work cause transaction.id does not name a field. Any idea? By "search" I mean be able to insert my transaction id inside the search box of the Shipment Admin page, press "search" and automatically retrieve appropriate transactions.

Solution 1

as with the other admin options, you need to use __ for foreign keys e.g.

search_fields = ['id', 'transaction__id']

Solution 2

search_fields documentation:

You can also perform a related lookup on a ForeignKey or ManyToManyField with the lookup API "follow" notation

Solution:

search_fields = ['id', 'transaction__id']