BEGIN;
BEGIN
EXPLAIN (ANALYZE, BUFFERS)
select
	cntrycode,
	count(*) as numcust,
	sum(c_acctbal) as totacctbal
from
	(
		select
			substr(c_phone, 1, 2) as cntrycode,
			c_acctbal
		from
			customer
		where
			substr(c_phone, 1, 2) in
				('28', '19', '16', '31', '15', '26', '21')
			and c_acctbal > (
				select
					avg(c_acctbal)
				from
					customer
				where
					c_acctbal > 0.00
					and substr(c_phone, 1, 2) in
						('28', '19', '16', '31', '15', '26', '21')
			)
			and not exists (
				select
					*
				from
					orders
				where
					o_custkey = c_custkey
			)
	) as vip
group by
	cntrycode
order by
	cntrycode;
                                                                             QUERY PLAN                                                                             
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=694109.79..694109.80 rows=3 width=20) (actual time=12616.713..12616.713 rows=7 loops=1)
   Sort Key: (substr((customer.c_phone)::text, 1, 2))
   Sort Method: quicksort  Memory: 25kB
   Buffers: shared hit=241794 read=85060 dirtied=253 written=27
   InitPlan 1 (returns $0)
     ->  Aggregate  (cost=52900.29..52900.30 rows=1 width=4) (actual time=813.933..813.933 rows=1 loops=1)
           Buffers: shared hit=9 read=36336 written=20
           ->  Bitmap Heap Scan on customer customer_1  (cost=6645.85..51945.81 rows=381789 width=4) (actual time=99.006..741.695 rows=382823 loops=1)
                 Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{28,19,16,31,15,26,21}'::text[])) AND (c_acctbal > 0::double precision))
                 Heap Blocks: exact=35278
                 Buffers: shared hit=9 read=36336 written=20
                 ->  Bitmap Index Scan on customer_c_phone_idx_c_acctbal  (cost=0.00..6550.41 rows=381789 width=0) (actual time=89.899..89.899 rows=382823 loops=1)
                       Index Cond: (substr((c_phone)::text, 1, 2) = ANY ('{28,19,16,31,15,26,21}'::text[]))
                       Buffers: shared hit=7 read=1060
   ->  HashAggregate  (cost=641209.42..641209.46 rows=3 width=20) (actual time=12616.652..12616.656 rows=7 loops=1)
         Group Key: substr((customer.c_phone)::text, 1, 2)
         Buffers: shared hit=241791 read=85060 dirtied=253 written=27
         ->  Hash Anti Join  (cost=597220.49..640769.18 rows=58699 width=20) (actual time=11878.611..12591.865 rows=63294 loops=1)
               Hash Cond: (customer.c_custkey = orders.o_custkey)
               Buffers: shared hit=241791 read=85060 dirtied=253 written=27
               ->  Bitmap Heap Scan on customer  (cost=2910.65..41865.22 rows=140060 width=24) (actual time=879.612..1446.581 rows=191417 loops=1)
                     Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{28,19,16,31,15,26,21}'::text[])) AND (c_acctbal > $0))
                     Heap Blocks: exact=35169
                     Buffers: shared hit=260 read=71801 written=20
                     ->  Bitmap Index Scan on customer_c_phone_idx  (cost=0.00..2875.63 rows=140060 width=0) (actual time=870.576..870.576 rows=191417 loops=1)
                           Index Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{28,19,16,31,15,26,21}'::text[])) AND (c_acctbal > $0))
                           Buffers: shared hit=19 read=36873 written=20
               ->  Hash  (cost=405686.04..405686.04 rows=15089904 width=4) (actual time=10028.180..10028.180 rows=15015000 loops=1)
                     Buckets: 16777216  Batches: 1  Memory Usage: 658944kB
                     Buffers: shared hit=241528 read=13259 dirtied=253 written=7
                     ->  Seq Scan on orders  (cost=0.00..405686.04 rows=15089904 width=4) (actual time=0.021..4658.578 rows=15015000 loops=1)
                           Buffers: shared hit=241528 read=13259 dirtied=253 written=7
 Planning time: 3.163 ms
 Execution time: 12638.769 ms
(34 rows)

COMMIT;
COMMIT