dbjobqueue: Filter maintenance queries based on results

Jobs that already had their results nulled, shouldn't be included in the
maintenance job.

cmd/osbuild-composer-dbjobqueue-tests/main_test.go

@@ -74,7 +74,7 @@ func setFinishedAt(t *testing.T, q *dbjobqueue.DBJobQueue, id uuid.UUID, finishe
 	started := finished.Add(-time.Second)
 	queued := started.Add(-time.Second)
 
-	_, err = conn.Exec(context.Background(), "UPDATE jobs SET queued_at = $1, started_at = $2, finished_at = $3 WHERE id = $4", queued, started, finished, id)
+	_, err = conn.Exec(context.Background(), "UPDATE jobs SET queued_at = $1, started_at = $2, finished_at = $3, result = '{\"result\": \"success\" }' WHERE id = $4", queued, started, finished, id)
 	require.NoError(t, err)
 }
 

internal/jobqueue/dbjobqueue/dbjobqueue.go

@@ -104,7 +104,7 @@ const (
 	sqlQueryJobsUptoByType = `
                 SELECT array_agg(id), type
                 FROM jobs
-                WHERE type = ANY($1) AND finished_at < $2
+                WHERE type = ANY($1) AND finished_at < $2 AND result IS NOT NULL
                 GROUP BY type`
 	sqlDeleteJobResult = `
                 UPDATE jobs