further improve overhead of database calls from `dequeue()`

[carmichaelong]

Some of the calls to the database could be fetching extra info from the database that is not necessary when initially filtering just a few trials from the larger database. We could consider using only() to initially only pull relevant columns for the larger filter, then let django do lazy loading of other info needed later (at the cost of extra, but smaller calls to the DB).

Example

for instance, this django code

# find trials with some videos not uploaded
not_uploaded = Video.objects.filter(video='',
                                    updated_at__gte=datetime.now() + timedelta(minutes=-15)).values_list("trial__id", flat=True)


if isMonoQuery == 'False':
    uploaded_trials = Trial.objects.filter(updated_at__gte=datetime.now() + timedelta(days=-7)).exclude(
                                            id__in=not_uploaded).exclude(session__isMono=True)
else:
    uploaded_trials = Trial.objects.filter(updated_at__gte=datetime.now() + timedelta(days=-7)).exclude(
                                            id__in=not_uploaded).filter(session__isMono=True)

leads to the SQL call

SELECT "mcserver_trial"."id", "mcserver_trial"."session_id", "mcserver_trial"."status", 
       "mcserver_trial"."name", "mcserver_trial"."meta", "mcserver_trial"."created_at", 
       "mcserver_trial"."updated_at", "mcserver_trial"."server", "mcserver_trial"."is_docker", 
       "mcserver_trial"."hostname", "mcserver_trial"."processed_duration", 
       "mcserver_trial"."processed_count", "mcserver_trial"."git_commit", 
       "mcserver_trial"."trashed", "mcserver_trial"."trashed_at"
FROM "mcserver_trial"
INNER JOIN "mcserver_session" 
    ON ("mcserver_trial"."session_id" = "mcserver_session"."id")
WHERE ("mcserver_trial"."updated_at" >= '2025-06-02T00:00:00+00:00'::timestamptz 
       AND NOT ("mcserver_trial"."id" IN (
            SELECT U0."trial_id" FROM "mcserver_video" U0 
            WHERE (U0."updated_at" >= '2025-06-09T00:00:00+00:00'::timestamptz 
                   AND U0."video" = '')
       )) 
       AND NOT ("mcserver_session"."isMono"));

The long SELECT call is likely due to some of the fields needed after a single trial is selected to update these fields.

Steps to try:

• use only() to reduce the first SELECT call (e.g., id, updated_at, isMono)
• let django lazy load some fields (e.g., status, server, processed_count)
• check the new SQL calls from django to see if it reduces overhead using EXPLAIN ANALYZE
• see if extra calls from the database are worth reducing the larger initial filter

[carmichaelong]

Better idea: create a partial index with updated_at and status='stopped' (or also status='reprocess'). Add something like the following chunk here.

class Meta:
        indexes = [
            models.Index(
                fields=["updated_at"],
                name="trial_updated_at_partial_idx_status",
                condition=Q(status__in=["stopped", "reprocess"]),
            ),
        ]

And then update the flow in dequeue() to take advantage of this call earlier to filter out more first, something like:

base_filter = Trial.objects.filter(
    status__in=['stopped', 'reprocess'],
    updated_at__gte=datetime.now() - timedelta(days=7)
).exclude(id__in=not_uploaded)

if isMonoQuery == 'False':
    uploaded_trials = base_filter.exclude(session__isMono=True)
else:
    uploaded_trials = base_filter.filter(session__isMono=True)