BEGIN;
BEGIN
EXPLAIN (ANALYZE, BUFFERS)
select
	c_count,
	count(*) as custdist
from
	(
		select
			c_custkey,
			count(o_orderkey)
		from
			customer left outer join orders on
				c_custkey = o_custkey
				and o_comment not like '%special%requests%'
		group by
			c_custkey
	) as c_orders (c_custkey, c_count)
group by
	c_count
order by
	custdist desc,
	c_count desc;
                                                                    QUERY PLAN                                                                    
--------------------------------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=851989.47..851989.97 rows=200 width=8) (actual time=31085.717..31085.718 rows=46 loops=1)
   Sort Key: (count(*)), (count(orders.o_orderkey))
   Sort Method: quicksort  Memory: 27kB
   Buffers: shared hit=201931 read=89151 written=384
   ->  HashAggregate  (cost=851979.83..851981.83 rows=200 width=8) (actual time=31085.608..31085.617 rows=46 loops=1)
         Group Key: count(orders.o_orderkey)
         Buffers: shared hit=201928 read=89151 written=384
         ->  HashAggregate  (cost=814479.83..829479.83 rows=1500000 width=8) (actual time=30258.271..30751.540 rows=1500000 loops=1)
               Group Key: customer.c_custkey
               Buffers: shared hit=201928 read=89151 written=384
               ->  Hash Right Join  (cost=69028.00..739410.74 rows=15013817 width=8) (actual time=1369.972..20449.523 rows=15352522 loops=1)
                     Hash Cond: (orders.o_custkey = customer.c_custkey)
                     Buffers: shared hit=201928 read=89151 written=384
                     ->  Seq Scan on orders  (cost=0.00..445175.49 rows=15013817 width=8) (actual time=0.032..9428.826 rows=14852503 loops=1)
                           Filter: ((o_comment)::text !~~ '%special%requests%'::text)
                           Rows Removed by Filter: 162497
                           Buffers: shared hit=198021 read=57780 written=123
                     ->  Hash  (cost=50278.00..50278.00 rows=1500000 width=4) (actual time=1361.068..1361.068 rows=1500000 loops=1)
                           Buckets: 2097152  Batches: 1  Memory Usage: 69119kB
                           Buffers: shared hit=3907 read=31371 written=261
                           ->  Seq Scan on customer  (cost=0.00..50278.00 rows=1500000 width=4) (actual time=0.019..885.385 rows=1500000 loops=1)
                                 Buffers: shared hit=3907 read=31371 written=261
 Planning time: 4.840 ms
 Execution time: 31114.528 ms
(24 rows)

COMMIT;
COMMIT