QUERY PLAN
Limit (cost=7.31..7.36 rows=20 width=253)
-> Sort (cost=7.31..7.43 rows=47 width=253)
Sort Key: created_at DESC
-> HashAggregate (cost=5.59..6.06 rows=47 width=253)
Group Key: id
-> Seq Scan on tbl_operation_tasks s (cost=0.00..5.47 rows=47 width=253)