Admin searchfields for inherited model

[Pavel Pančocha]

Hello everyone!

Let's have model Payer and we will create ExtendedPayer from it

class ExtendedPayer(Payer):
    ...

We create admin for ExtendedPayer and define search fields. We want to be able to filter by pk of Payer. So I would expect these to work the same:

class ExtendedPayerAdmin(ModelAdmin):
    ...
    search_fields = (
        "pk__iexact", ...
    )
    ...

class ExtendedPayerAdmin(ModelAdmin):
    ...
    search_fields = (
        "id__iexact", ...
    )
    ...

Guess what? The "id" variant works ok and the "pk" fails with

Why? Because in construct_search (​See Git) it's transformed to pk__iexact__icontains as it found out that the pk is payer_ptr which is FK.

If we want to be correct, it should be "payer_ptr__pk__iexact".

Please let me know if this behaviour is a bug or if is there any reason behind it.