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
				('31', '28', '19', '23', '27', '14', '21')
			and c_acctbal > (
				select
					avg(c_acctbal)
				from
					customer
				where
					c_acctbal > 0.00
					and substr(c_phone, 1, 2) in
						('31', '28', '19', '23', '27', '14', '21')
			)
			and not exists (
				select
					*
				from
					orders
				where
					o_custkey = c_custkey
			)
	) as vip
group by
	cntrycode
order by
	cntrycode;
                                                                              QUERY PLAN                                                                              
----------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=695290.56..695290.57 rows=3 width=20) (actual time=12442.895..12442.896 rows=7 loops=1)
   Sort Key: (substr((customer.c_phone)::text, 1, 2))
   Sort Method: quicksort  Memory: 25kB
   Buffers: shared hit=172271 read=155084 written=154
   InitPlan 1 (returns $0)
     ->  Aggregate  (cost=52905.17..52905.18 rows=1 width=4) (actual time=1195.144..1195.144 rows=1 loops=1)
           Buffers: shared hit=10 read=36332 written=28
           ->  Bitmap Heap Scan on customer customer_1  (cost=6646.88..51950.36 rows=381923 width=4) (actual time=202.158..1072.373 rows=381775 loops=1)
                 Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{31,28,19,23,27,14,21}'::text[])) AND (c_acctbal > 0::double precision))
                 Heap Blocks: exact=35278
                 Buffers: shared hit=10 read=36332 written=28
                 ->  Bitmap Index Scan on customer_c_phone_idx_c_acctbal  (cost=0.00..6551.40 rows=381923 width=0) (actual time=182.001..182.001 rows=381775 loops=1)
                       Index Cond: (substr((c_phone)::text, 1, 2) = ANY ('{31,28,19,23,27,14,21}'::text[]))
                       Buffers: shared hit=8 read=1056 written=1
   ->  HashAggregate  (cost=642385.31..642385.35 rows=3 width=20) (actual time=12442.825..12442.828 rows=7 loops=1)
         Group Key: substr((customer.c_phone)::text, 1, 2)
         Buffers: shared hit=172268 read=155084 written=154
         ->  Hash Anti Join  (cost=598404.87..641943.14 rows=58956 width=20) (actual time=12039.634..12421.629 rows=63304 loops=1)
               Hash Cond: (customer.c_custkey = orders.o_custkey)
               Buffers: shared hit=172268 read=155084 written=154
               ->  Bitmap Heap Scan on customer  (cost=2910.08..41863.26 rows=140007 width=24) (actual time=1297.915..1547.530 rows=190628 loops=1)
                     Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{31,28,19,23,27,14,21}'::text[])) AND (c_acctbal > $0))
                     Heap Blocks: exact=35167
                     Buffers: shared hit=34679 read=37375 written=29
                     ->  Bitmap Index Scan on customer_c_phone_idx  (cost=0.00..2875.07 rows=140007 width=0) (actual time=1285.364..1285.364 rows=190628 loops=1)
                           Index Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{31,28,19,23,27,14,21}'::text[])) AND (c_acctbal > $0))
                           Buffers: shared hit=21 read=36866 written=29
               ->  Hash  (cost=406494.91..406494.91 rows=15119991 width=4) (actual time=10605.816..10605.816 rows=15015000 loops=1)
                     Buckets: 16777216  Batches: 1  Memory Usage: 658944kB
                     Buffers: shared hit=137586 read=117709 written=125
                     ->  Seq Scan on orders  (cost=0.00..406494.91 rows=15119991 width=4) (actual time=0.043..5521.970 rows=15015000 loops=1)
                           Buffers: shared hit=137586 read=117709 written=125
 Planning time: 4.477 ms
 Execution time: 12460.110 ms
(34 rows)

COMMIT;
COMMIT