#29314: PostgreSQL error when using a TextField generic object ID field, an 
PK, and GenericRelation
               Reporter:  Kye        |          Owner:  nobody
  Russell                            |
                   Type:  Bug        |         Status:  new
              Component:  Database   |        Version:  1.11
  layer (models, ORM)                |
               Severity:  Normal     |       Keywords:  orm, postgres
           Triage Stage:             |      Has patch:  0
  Unreviewed                         |
    Needs documentation:  0          |    Needs tests:  0
Patch needs improvement:  0          |  Easy pickings:  0
                  UI/UX:  0          |
 I'm still unsure if this is a Django bug or incorrect usage on my part, so
 please close this ticket if it's the latter.

 I have a fairly basic looking Django model with a generic relationship:

 class AttachedMediaItem(models.Model):

     # Generic relation to another object.
     parent_content_type = models.ForeignKey(
     parent_object_id = models.TextField(db_index=True)
     parent_content_object = GenericForeignKey('parent_content_type',

 (irrelevant fields removed)

 I inherited this codebase so I cannot fully justify all design decisions,
 however I believe parent_object_id is a TextField to support non-integer
 PKs on the related object (e.g. UUIDs). This model tends to relate to a
 wide variety of other models, so it needs to be very versatile in terms of
 what PK types it supports.

 This is as-per the Django docs recommendations:

 Now, this model:

 class UnitType(models.Model):

     media = GenericRelation('media.AttachedMediaItem',

 (irrelevant fields removed).

 Note that I'm leaving the PK generation up to Django, meaning I'll get an
 integer PK for this model.

 Now, if I run this


 An SQL error manages to bubble through the ORM:

 ProgrammingError: operator does not exist: integer = text
 LINE 1: ...a_attachedmediaitem" ON ("products_unittype"."id" = "media_a...
 HINT:  No operator matches the given name and argument type(s). You might
 need to add explicit type casts.

 My understanding is that this is due to the difference in PK fields.

 I believe I have followed the prescribed best practice as per the Django
 documentation (relevant section linked above). I feel that at the very
 least this shouldn't result in a somewhat cryptic PostgreSQL error.

 Is this a genuine Django bug, or misuse on my part?

Ticket URL: <https://code.djangoproject.com/ticket/29314>
Django <https://code.djangoproject.com/>
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