QUERY PLAN
Limit (cost=5891.66..5891.66 rows=1 width=155)
-> Sort (cost=5891.66..5891.66 rows=1 width=155)
Sort Key: created_at DESC
-> Seq Scan on tbl_comments (cost=0.00..5891.65 rows=1 width=155)
Filter: ((parent IS NULL) AND (object_type IS NULL) AND (object_id IS NULL))