Django's SQL query has repeated subquery when using filters with annotations and subqueries

I have Camp Model that stores dates as an array of strings in a Json field. I'm trying to optimize a database query to retrieve Camp objects with future dates.

class Camp(models.Model):
    dates = models.JSONField(default=None, blank=True, null=True, validators= [datesListValidator])

I'm using annotations and subqueries to filter out instances of that model where none of the dates are equal to or greater than the current date (basically I only want camps that have a date in the future). I'm using annotations and Subqueries to get the "max_date" from the dates for each camp and then filtering the camps based on the "max_date"

I'm trying to optimize this filtering process, as getting all the camps and then filtering it in Python is too slow for my use case and as more time goes on the number of Camps that have to be filtered out would just keep increasing.

The solution i came up with gives me the results I need, but the generated SQL query has multiple runs of the same subquery which I don't need. I'd like to avoid doing this using RawSQL and would like to find a way to achieve my desired result using the django ORM functions. I'm using PostgreSQL and i'm open to using any built in features it provides.

I made this function to get the camps I need

def get_future_camps():
    """
    Retrieves all Camp objects where the latest date in the 'dates' JSONB field is today or in the future.
    Returns a QuerySet with only relevant fields.
    """
    today_str = now().date().isoformat()

    camps_with_max = Camp.objects.annotate(
        max_date=Subquery(
            Camp.objects.filter(
                id=OuterRef("id")
            ).annotate(
                extracted_dates=JsonbArrayElementsText(F("dates"))
            ).values_list("extracted_dates", flat=True).order_by("-extracted_dates")[:1]
        )
    )

    return camps_with_max.filter(
        max_date__gte=today_str
    ).only("id", "pk")

# This only works for Postgres
class JsonbArrayElementsText(Func):
    """
    A custom function to extract elements from a JSONB array as text.
    """
    function = 'jsonb_array_elements_text'
    output_field = CharField()

This generated this SQL query

SELECT "my_project_camp"."id",

       (

        SELECT jsonb_array_elements_text(U0."dates") AS "extracted_dates"

          FROM "my_project_camp" U0

         WHERE U0."id" = "my_project_camp"."id"

         ORDER BY 1 DESC

         LIMIT 1

       ) AS "max_date"

  FROM "my_project_camp"

 WHERE (

        SELECT jsonb_array_elements_text(U0."dates") AS "extracted_dates"

          FROM "my_project_camp" U0

         WHERE U0."id" = "my_project_camp"."id"

         ORDER BY 1 DESC

         LIMIT 1

       ) >= '''2025-03-08'''

This uses the same Subquery to get the "max_date" twice. After looking it up I found that WHERE clauses are evaluated before SELECT so you can't use aliases in the WHERE clause

My question is: Is there a way to remove the extra subquery call? I'm using only so I don't need to use the max_date field outside of the filter itself and the whole point of doing this was to optimize getting future camps

class Camp(models.Model):
    # no dates
    # …
    pass


class CampDate(models.Model):
    camp = models.ForeignKey(Camp, on_delete=models.PROTECT)
    date = models.DateField()

from django.utils.timezone import now

today_str = now().date()
Camp.objects.filter(campdate__date__gte=today_str).distinct()