QUERY PLAN                                                                        
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 Seq Scan on box b  (cost=0.00..3669095.76 rows=128 width=8) (actual time=0.047..6938.165 rows=128 loops=1)
   SubPlan 1
     ->  Hash Anti Join  (cost=14742.77..28664.79 rows=19239 width=8) (actual time=48.385..53.361 rows=1 loops=128)
           Hash Cond: (m1.box_id = m2.box_id)
           Join Filter: (m1.id < m2.id)
           ->  Bitmap Heap Scan on message m1  (cost=544.16..13696.88 rows=28858 width=16) (actual time=1.928..5.502 rows=17875 loops=128)
                 Recheck Cond: (box_id = b.id)
                 ->  Bitmap Index Scan on "message_box_Idx"  (cost=0.00..536.94 rows=28858 width=0) (actual time=1.797..1.797 rows=18487 loops=128)
                       Index Cond: (box_id = b.id)
           ->  Hash  (cost=13696.88..13696.88 rows=28858 width=16) (actual time=11.603..11.603 rows=20248 loops=113)
                 Buckets: 4096  Batches: 4 (originally 2)  Memory Usage: 1423kB
                 ->  Bitmap Heap Scan on message m2  (cost=544.16..13696.88 rows=28858 width=16) (actual time=1.838..6.886 rows=20248 loops=113)
                       Recheck Cond: (box_id = b.id)
                       ->  Bitmap Index Scan on "message_box_Idx"  (cost=0.00..536.94 rows=28858 width=0) (actual time=1.743..1.743 rows=20903 loops=113)
                             Index Cond: (box_id = b.id)
 Total runtime: 6940.369 ms