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', '12', '22', '25', '21', '34', '26')
			and c_acctbal > (
				select
					avg(c_acctbal)
				from
					customer
				where
					c_acctbal > 0.00
					and substr(c_phone, 1, 2) in
						('18', '12', '22', '25', '21', '34', '26')
			)
			and not exists (
				select
					*
				from
					orders
				where
					o_custkey = c_custkey
			)
	) as vip
group by
	cntrycode
order by
	cntrycode;
                                                                             QUERY PLAN                                                                             
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=695924.22..695924.23 rows=3 width=20) (actual time=12216.597..12216.598 rows=7 loops=1)
   Sort Key: (substr((public.customer.c_phone)::text, 1, 2))
   Sort Method: quicksort  Memory: 25kB
   Buffers: shared hit=326001 read=1597
   InitPlan 1 (returns $0)
     ->  Aggregate  (cost=52900.99..52901.00 rows=1 width=4) (actual time=498.083..498.083 rows=1 loops=1)
           Buffers: shared hit=35287 read=1056
           ->  Bitmap Heap Scan on customer  (cost=6645.14..51946.39 rows=381838 width=4) (actual time=92.174..416.512 rows=381671 loops=1)
                 Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{18,12,22,25,21,34,26}'::text[])) AND (c_acctbal > 0::double precision))
                 Buffers: shared hit=35287 read=1056
                 ->  Bitmap Index Scan on customer_c_phone_idx_c_acctbal  (cost=0.00..6549.68 rows=381838 width=0) (actual time=83.010..83.010 rows=381671 loops=1)
                       Index Cond: (substr((c_phone)::text, 1, 2) = ANY ('{18,12,22,25,21,34,26}'::text[]))
                       Buffers: shared hit=9 read=1056
   ->  HashAggregate  (cost=643023.16..643023.21 rows=3 width=20) (actual time=12216.531..12216.535 rows=7 loops=1)
         Buffers: shared hit=325999 read=1597
         ->  Hash Anti Join  (cost=598995.30..642578.34 rows=59309 width=20) (actual time=11688.323..12193.653 rows=63468 loops=1)
               Hash Cond: (public.customer.c_custkey = orders.o_custkey)
               Buffers: shared hit=325999 read=1597
               ->  Bitmap Heap Scan on customer  (cost=2910.36..41867.12 rows=140143 width=24) (actual time=562.770..733.914 rows=190813 loops=1)
                     Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{18,12,22,25,21,34,26}'::text[])) AND (c_acctbal > $0))
                     Buffers: shared hit=70448 read=1597
                     ->  Bitmap Index Scan on customer_c_phone_idx  (cost=0.00..2875.33 rows=140143 width=0) (actual time=553.621..553.621 rows=190813 loops=1)
                           Index Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{18,12,22,25,21,34,26}'::text[])) AND (c_acctbal > $0))
                           Buffers: shared hit=35297 read=1595
               ->  Hash  (cost=406897.75..406897.75 rows=15134975 width=4) (actual time=11114.097..11114.097 rows=15015000 loops=1)
                     Buckets: 2097152  Batches: 1  Memory Usage: 527872kB
                     Buffers: shared hit=255548
                     ->  Seq Scan on orders  (cost=0.00..406897.75 rows=15134975 width=4) (actual time=0.015..4734.967 rows=15015000 loops=1)
                           Buffers: shared hit=255548
 Total runtime: 12359.876 ms
(30 rows)

COMMIT;
COMMIT