QUERY PLAN
GroupAggregate (cost=157.35..157.47 rows=6 width=12)
Group Key: parent_id
-> Sort (cost=157.35..157.37 rows=9 width=4)
Sort Key: parent_id
-> Seq Scan on tbl_tasks (cost=0.00..157.20 rows=9 width=4)
Filter: (parent_id = ANY ('{1600,1598,1595,1592,1591,1583,1537,1536,1535}'::integer[]))