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
				('21', '13', '23', '22', '18', '25', '19')
			and c_acctbal > (
				select
					avg(c_acctbal)
				from
					customer
				where
					c_acctbal > 0.00
					and substr(c_phone, 1, 2) in
						('21', '13', '23', '22', '18', '25', '19')
			)
			and not exists (
				select
					*
				from
					orders
				where
					o_custkey = c_custkey
			)
	) as vip
group by
	cntrycode
order by
	cntrycode;
                                                                             QUERY PLAN                                                                             
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=694025.98..694025.98 rows=3 width=20) (actual time=11239.111..11239.112 rows=7 loops=1)
   Sort Key: (substr((customer.c_phone)::text, 1, 2))
   Sort Method: quicksort  Memory: 25kB
   Buffers: shared hit=113106 read=213748 dirtied=253 written=8930
   InitPlan 1 (returns $0)
     ->  Aggregate  (cost=52856.60..52856.61 rows=1 width=4) (actual time=533.675..533.675 rows=1 loops=1)
           Buffers: shared hit=28331 read=8012 written=679
           ->  Bitmap Heap Scan on customer customer_1  (cost=6636.58..51905.12 rows=380592 width=4) (actual time=80.278..460.574 rows=381981 loops=1)
                 Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{21,13,23,22,18,25,19}'::text[])) AND (c_acctbal > 0::double precision))
                 Heap Blocks: exact=35278
                 Buffers: shared hit=28331 read=8012 written=679
                 ->  Bitmap Index Scan on customer_c_phone_idx_c_acctbal  (cost=0.00..6541.43 rows=380592 width=0) (actual time=72.754..72.754 rows=381981 loops=1)
                       Index Cond: (substr((c_phone)::text, 1, 2) = ANY ('{21,13,23,22,18,25,19}'::text[]))
                       Buffers: shared hit=11 read=1054 written=88
   ->  HashAggregate  (cost=641169.30..641169.34 rows=3 width=20) (actual time=11239.046..11239.047 rows=7 loops=1)
         Group Key: substr((customer.c_phone)::text, 1, 2)
         Buffers: shared hit=113103 read=213748 dirtied=253 written=8930
         ->  Hash Anti Join  (cost=597215.04..640729.98 rows=58576 width=20) (actual time=10563.338..11216.208 rows=63447 loops=1)
               Hash Cond: (customer.c_custkey = orders.o_custkey)
               Buffers: shared hit=113103 read=213748 dirtied=253 written=8930
               ->  Bitmap Heap Scan on customer  (cost=2905.20..41845.91 rows=139532 width=24) (actual time=591.234..1066.189 rows=190594 loops=1)
                     Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{21,13,23,22,18,25,19}'::text[])) AND (c_acctbal > $0))
                     Heap Blocks: exact=35172
                     Buffers: shared hit=28343 read=43718 written=866
                     ->  Bitmap Index Scan on customer_c_phone_idx  (cost=0.00..2870.31 rows=139532 width=0) (actual time=583.338..583.338 rows=190594 loops=1)
                           Index Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{21,13,23,22,18,25,19}'::text[])) AND (c_acctbal > $0))
                           Buffers: shared hit=28341 read=8548 written=744
               ->  Hash  (cost=405686.04..405686.04 rows=15089904 width=4) (actual time=9862.217..9862.217 rows=15000000 loops=1)
                     Buckets: 16777216  Batches: 1  Memory Usage: 658416kB
                     Buffers: shared hit=84757 read=170030 dirtied=253 written=8064
                     ->  Seq Scan on orders  (cost=0.00..405686.04 rows=15089904 width=4) (actual time=0.019..4993.946 rows=15000000 loops=1)
                           Buffers: shared hit=84757 read=170030 dirtied=253 written=8064
 Planning time: 2.661 ms
 Execution time: 11256.257 ms
(34 rows)

COMMIT;
COMMIT