_get_returning_qs does not fetch foreign keys in the RETURNING statement.

[proofit404]

Hi,

Thanks for the amazing library!

I spend some time looking into a strange N+1 issue on our production system. We have a model defining like this:

class Subscription(TimeStampedModel, SoftDeletableModel, UpdateReturningModel):
    member = ForeignKey(
        settings.AUTH_USER_MODEL,
        related_name="subscriptions",
        on_delete=CASCADE,
    )
    unread_count = IntegerField()

We apply this code to make bulk update counters of many users:

def save_unread_counters(users, counter=1):
    return dict(
        models.Subscription.objects.filter(member__in=users)
        .update_returning(unread_count=F("unread_count") + counter)
        .values_list("member_id", "unread_count")
    )

It will generate following SQL queries:

UPDATE "subscription"
SET "unread_count" = ("subscription"."unread_count" + 1)
WHERE ("subscription"."is_removed" = FALSE
       AND "subscription"."member_id" IN (1518, 1519))
RETURNING "id", "created", "modified", "is_removed", "unread_count"

SELECT "subscription"."id",
       "subscription"."member_id"
FROM "subscription"
WHERE "subscription"."id" = 1515

SELECT "subscription"."id",
       "subscription"."member_id"
FROM "subscription"
WHERE "subscription"."id" = 1516

Looks like _get_returning_qs manager method does not take foreign keys into account when it build field argument.

In the values_list method of the ReturningQuerySet have this line https://github.com/M1hacka/django-pg-returning/blob/d615ee52311fa573d528740a5f1136ddd92585ff/src/django_pg_returning/queryset.py#L116
Where getattr of the member_id load it from the database each time.

Regards, Artem.

[M1ha-Shvn]

Will be released with version 1.1.1

[proofit404]

Thank you so much!