qplan

QUERY PLAN
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Limit  (cost=4570.58..4570.63 rows=100 width=144) (actual time=698.845..699.122 rows=100 loops=1)
  ->  Sort  (cost=4570.58..4610.25 rows=79351 width=144) (actual time=698.842..698.945 rows=100 loops=1)
        Sort Key: orders.created_at, orders.id
        Sort Method: top-N heapsort  Memory: 47kB
        ->  Hash Join  (cost=2077.79..3964.03 rows=79351 width=144) (actual time=189.178..586.378 rows=79038 loops=1)
              Hash Cond: (group_assignments.groupable_id = orders.id)
              ->  Seq Scan on group_assignments  (cost=0.00..1410.13 rows=79351 width=4) (actual time=0.475..112.457 rows=79038 loops=1)
                    Filter: (((groupable_type)::text = 'Order'::text) AND (group_id = 1))
                    Rows Removed by Filter: 34245
              ->  Hash  (cost=1801.13..1801.13 rows=79045 width=144) (actual time=188.658..188.658 rows=79045 loops=1)
                    Buckets: 8192  Batches: 1  Memory Usage: 12451kB
                    ->  Seq Scan on orders  (cost=0.00..1801.13 rows=79045 width=144) (actual time=0.006..80.690 rows=79045 loops=1)
Total runtime: 699.291 ms
(13 rows)