[Django] #30099: Filter by Count annotated inside Subquery

[Django]

#30099: Filter by Count annotated inside Subquery
-------------------------------------+-------------------------------------
               Reporter:  MrFus10n   |          Owner:  nobody
                   Type:  Bug        |         Status:  new
              Component:  Database   |        Version:  2.1
  layer (models, ORM)                |
               Severity:  Normal     |       Keywords:
           Triage Stage:             |      Has patch:  0
  Unreviewed                         |
    Needs documentation:  0          |    Needs tests:  0
Patch needs improvement:  0          |  Easy pickings:  0
                  UI/UX:  0          |
-------------------------------------+-------------------------------------
 I want to get authors and annotate minimal count of books in category if
 it is greater than three.

 Book and Author models and are not connected with ForeignKey fields (this
 is, abstract and simplified, there is a reason):

 {{{
 Author(models.Model):
     name = models.CharField(max_length=250)

 Book(models.Model):
     author_name = models.CharField(max_length=250)
     book_category = models.CharField(max_length=250)
 }}}

 Here is simplest query I can get to reproduce:

 {{{
 (Author.objects
  .annotate(min_valuable_count=Subquery(
     Book.objects
         .filter(author_name=OuterRef('name'))
         .annotate(cnt=Count('book_category'))
         .filter(cnt__gt=3)
         .order_by('cnt')
         .values('cnt')[:1],
     output_field=models.IntegerField()
 )))
 }}}

 And I get an error:

 {{{
 psycopg2.ProgrammingError: missing FROM-clause entry for table "U0"
 LINE 1: ... "core_author" GROUP BY "core_author"."id", "U0"."id" ...
                                                        ^
 }}}

 Here is SQL:

 {{{
 SELECT "core_author"."id", "core_author"."name", (
     SELECT COUNT(U0."book_category") AS "cnt"
     FROM "core_book" U0 WHERE U0."id" = ("core_author"."chat_id")
     GROUP BY U0."id" HAVING COUNT(U0."book_category") > 3
     ORDER BY "cnt" ASC  LIMIT 1)
 AS "min_valuable_count"
 FROM "core_author"
 GROUP BY "core_author"."id", "U0"."id"
 }}}

 If I remove line {{{.filter(author_name=OuterRef('name'))}}} or
 {{{.filter(cnt__gt=3)}}} query stops raising error.

-- 
Ticket URL: <https://code.djangoproject.com/ticket/30099>
Django <https://code.djangoproject.com/>
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