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
				('20', '29', '28', '14', '27', '31', '21')
			and c_acctbal > (
				select
					avg(c_acctbal)
				from
					customer
				where
					c_acctbal > 0.00
					and substr(c_phone, 1, 2) in
						('20', '29', '28', '14', '27', '31', '21')
			)
			and not exists (
				select
					*
				from
					orders
				where
					o_custkey = c_custkey
			)
	) as vip
group by
	cntrycode
order by
	cntrycode;
                                                                             QUERY PLAN                                                                             
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=695907.11..695907.12 rows=3 width=20) (actual time=9454.984..9454.985 rows=7 loops=1)
   Sort Key: (substr((customer.c_phone)::text, 1, 2))
   Sort Method: quicksort  Memory: 25kB
   Buffers: shared hit=314524 read=13081
   InitPlan 1 (returns $0)
     ->  Aggregate  (cost=52918.03..52918.04 rows=1 width=4) (actual time=469.651..469.651 rows=1 loops=1)
           Buffers: shared hit=25393 read=10948
           ->  Bitmap Heap Scan on customer customer_1  (cost=6649.65..51962.34 rows=382274 width=4) (actual time=78.511..400.371 rows=381692 loops=1)
                 Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{20,29,28,14,27,31,21}'::text[])) AND (c_acctbal > 0::double precision))
                 Heap Blocks: exact=35278
                 Buffers: shared hit=25393 read=10948
                 ->  Bitmap Index Scan on customer_c_phone_idx_c_acctbal  (cost=0.00..6554.08 rows=382274 width=0) (actual time=70.708..70.708 rows=381692 loops=1)
                       Index Cond: (substr((c_phone)::text, 1, 2) = ANY ('{20,29,28,14,27,31,21}'::text[]))
                       Buffers: shared hit=11 read=1052
   ->  HashAggregate  (cost=642989.01..642989.05 rows=3 width=20) (actual time=9454.908..9454.910 rows=7 loops=1)
         Group Key: substr((customer.c_phone)::text, 1, 2)
         Buffers: shared hit=314521 read=13081
         ->  Hash Anti Join  (cost=598996.45..642547.74 rows=58835 width=20) (actual time=9180.326..9436.298 rows=63696 loops=1)
               Hash Cond: (customer.c_custkey = orders.o_custkey)
               Buffers: shared hit=314521 read=13081
               ->  Bitmap Heap Scan on customer  (cost=2911.51..41868.40 rows=140148 width=24) (actual time=525.812..647.065 rows=190793 loops=1)
                     Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{20,29,28,14,27,31,21}'::text[])) AND (c_acctbal > $0))
                     Heap Blocks: exact=35163
                     Buffers: shared hit=60567 read=11484
                     ->  Bitmap Index Scan on customer_c_phone_idx  (cost=0.00..2876.47 rows=140148 width=0) (actual time=517.882..517.882 rows=190793 loops=1)
                           Index Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{20,29,28,14,27,31,21}'::text[])) AND (c_acctbal > $0))
                           Buffers: shared hit=25404 read=11484
               ->  Hash  (cost=406897.75..406897.75 rows=15134975 width=4) (actual time=8547.659..8547.659 rows=15015000 loops=1)
                     Buckets: 16777216  Batches: 1  Memory Usage: 658944kB
                     Buffers: shared hit=253951 read=1597
                     ->  Seq Scan on orders  (cost=0.00..406897.75 rows=15134975 width=4) (actual time=0.027..3780.960 rows=15015000 loops=1)
                           Buffers: shared hit=253951 read=1597
 Planning time: 2.258 ms
 Execution time: 9489.252 ms
(34 rows)

COMMIT;
COMMIT