id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
30099	Filter by Count annotated inside Subquery	MrFus10n	nobody	"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(cnt__gt=3)}}}, last {{{GROUP BY}}} disappears and query stops raising error:

{{{
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""
}}}

Is there any way to remove GROUP BY in outer query without removing .filter(cnt__gt=3) in subquery?"	Bug	new	Database layer (models, ORM)	2.1	Normal		Subquery annotate Count filter		Unreviewed	0	0	0	0	0	0