QUERY PLAN
Aggregate (cost=61.58..61.59 rows=1 width=8)
-> Sort (cost=60.58..60.75 rows=67 width=228)
Sort Key: s.created_at
-> HashAggregate (cost=57.88..58.55 rows=67 width=228)
Group Key: s.id, u.id
-> Hash Left Join (cost=9.24..57.54 rows=67 width=16)
Hash Cond: (s.head_of = u.id)
-> Seq Scan on tbl_tasks s (cost=0.00..48.12 rows=67 width=24)
Filter: ((parent_id IS NULL) AND (task_group_id = 106))
-> Hash (cost=7.44..7.44 rows=144 width=4)
-> Seq Scan on tbl_users u (cost=0.00..7.44 rows=144 width=4)