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
				('18', '14', '17', '20', '15', '28', '31')
			and c_acctbal > (
				select
					avg(c_acctbal)
				from
					customer
				where
					c_acctbal > 0.00
					and substr(c_phone, 1, 2) in
						('18', '14', '17', '20', '15', '28', '31')
			)
			and not exists (
				select
					*
				from
					orders
				where
					o_custkey = c_custkey
			)
	) as vip
group by
	cntrycode
order by
	cntrycode;
                                                                             QUERY PLAN                                                                             
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=691854.37..691854.38 rows=3 width=20) (actual time=10023.089..10023.090 rows=7 loops=1)
   Sort Key: (substr((customer.c_phone)::text, 1, 2))
   Sort Method: quicksort  Memory: 25kB
   Buffers: shared hit=322243 read=3601
   InitPlan 1 (returns $0)
     ->  Aggregate  (cost=52962.36..52962.37 rows=1 width=4) (actual time=537.736..537.736 rows=1 loops=1)
           Buffers: shared hit=35740 read=604
           ->  Bitmap Heap Scan on customer customer_1  (cost=6677.94..52005.28 rows=382832 width=4) (actual time=92.931..457.926 rows=382499 loops=1)
                 Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{18,14,17,20,15,28,31}'::text[])) AND (c_acctbal > 0::double precision))
                 Heap Blocks: exact=35278
                 Buffers: shared hit=35740 read=604
                 ->  Bitmap Index Scan on customer_c_phone_idx_c_acctbal  (cost=0.00..6582.23 rows=382832 width=0) (actual time=83.509..83.509 rows=382499 loops=1)
                       Index Cond: (substr((c_phone)::text, 1, 2) = ANY ('{18,14,17,20,15,28,31}'::text[]))
                       Buffers: shared hit=462 read=604
   ->  HashAggregate  (cost=638891.94..638891.98 rows=3 width=20) (actual time=10023.035..10023.037 rows=7 loops=1)
         Group Key: substr((customer.c_phone)::text, 1, 2)
         Buffers: shared hit=322240 read=3601
         ->  Hash Anti Join  (cost=594890.80..638448.72 rows=59096 width=20) (actual time=9657.155..10002.372 rows=63660 loops=1)
               Hash Cond: (customer.c_custkey = orders.o_custkey)
               Buffers: shared hit=322240 read=3601
               ->  Bitmap Heap Scan on customer  (cost=2941.52..41903.44 rows=140340 width=24) (actual time=603.043..833.379 rows=191111 loops=1)
                     Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{18,14,17,20,15,28,31}'::text[])) AND (c_acctbal > $0))
                     Heap Blocks: exact=35172
                     Buffers: shared hit=71142 read=921
                     ->  Bitmap Index Scan on customer_c_phone_idx  (cost=0.00..2906.43 rows=140340 width=0) (actual time=593.886..593.886 rows=191111 loops=1)
                           Index Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{18,14,17,20,15,28,31}'::text[])) AND (c_acctbal > $0))
                           Buffers: shared hit=35981 read=910
               ->  Hash  (cost=404074.68..404074.68 rows=15029968 width=4) (actual time=9000.249..9000.249 rows=15015000 loops=1)
                     Buckets: 16777216  Batches: 1  Memory Usage: 658944kB
                     Buffers: shared hit=251095 read=2680
                     ->  Seq Scan on orders  (cost=0.00..404074.68 rows=15029968 width=4) (actual time=0.020..4695.190 rows=15015000 loops=1)
                           Buffers: shared hit=251095 read=2680
 Planning time: 2.594 ms
 Execution time: 10028.420 ms
(34 rows)

COMMIT;
COMMIT