#29294: ModelAdmin.raw_id_fields should be included in select_related() by
change_view and used by raw id widget
               Reporter:  Yurii Zolot'ko        |          Owner:  nobody
                   Type:  Cleanup/optimization  |         Status:  new
              Component:  contrib.admin         |        Version:  1.11
               Severity:  Normal                |       Keywords:
           Triage Stage:  Unreviewed            |      Has patch:  0
    Needs documentation:  0                     |    Needs tests:  0
Patch needs improvement:  0                     |  Easy pickings:  0
                  UI/UX:  0                     |
 Consider model A having many ForeignKey relationships to other models
 B,C,D...Z (common case in many applications).
 ModelAdmin has `raw_id_fields` optimization option to avoid querying full
 contents of B...Z tables every time.
 However in some cases this optimization is not enough as it still invokes
 several queries to B... tables to fetch single row from every of them to
 display `__str__` and url of related object next to raw input field when
 admin's change_view is opened for single object.
 So when there are 3 ForeignKeys there will at least 4 queries per request
 (1 for object itself, 3 for every ForeignKey). When there are 10
 ForeignKeys there will be 11 queries per request and so on resulting in
 very high response time for complex objects even using raw_id_fields.
 It looks like this problem is not possible to avoid now. I've tried to
 override get_queryset() method of ModelAdmin to select_related()
 raw_id_fields like this:

 class ObjectAdmin(admin.ModelAdmin):
     raw_id_fields = (
         'field1', 'field2', ...)

     def get_queryset(self, request):
         qs = admin.ModelAdmin.get_queryset(self, request)
         return qs.select_related(*self.raw_id_fields)

 still invokes separate query for every ForeignKey relationship instead of
 getting it from attribute of already fetched object resulting in high
 response times of admin interface impossible to improve.

 It would be significant performance improvement if ModelAdmin could
 select_related() `raw_id_fields` by default and ForeignKeyRawIdWidget
 wouldn't do extra queries for every related object when all necessary data
 is already present.

Ticket URL: <https://code.djangoproject.com/ticket/29294>
Django <https://code.djangoproject.com/>
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