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', '30', '27', '17', '21', '15', '16')
			and c_acctbal > (
				select
					avg(c_acctbal)
				from
					customer
				where
					c_acctbal > 0.00
					and substr(c_phone, 1, 2) in
						('20', '30', '27', '17', '21', '15', '16')
			)
			and not exists (
				select
					*
				from
					orders
				where
					o_custkey = c_custkey
			)
	) as vip
group by
	cntrycode
order by
	cntrycode;
                                                                             QUERY PLAN                                                                             
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Sort  (cost=693546.97..693546.98 rows=3 width=20) (actual time=11305.215..11305.215 rows=7 loops=1)
   Sort Key: (substr((customer.c_phone)::text, 1, 2))
   Sort Method: quicksort  Memory: 25kB
   Buffers: shared hit=281853 read=44765 dirtied=94 written=10
   InitPlan 1 (returns $0)
     ->  Aggregate  (cost=52915.14..52915.15 rows=1 width=4) (actual time=778.366..778.366 rows=1 loops=1)
           Buffers: shared hit=14 read=36329
           ->  Bitmap Heap Scan on customer customer_1  (cost=6649.00..51959.65 rows=382196 width=4) (actual time=90.069..706.901 rows=382517 loops=1)
                 Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{20,30,27,17,21,15,16}'::text[])) AND (c_acctbal > 0::double precision))
                 Heap Blocks: exact=35278
                 Buffers: shared hit=14 read=36329
                 ->  Bitmap Index Scan on customer_c_phone_idx_c_acctbal  (cost=0.00..6553.45 rows=382196 width=0) (actual time=81.601..81.601 rows=382517 loops=1)
                       Index Cond: (substr((c_phone)::text, 1, 2) = ANY ('{20,30,27,17,21,15,16}'::text[]))
                       Buffers: shared hit=11 read=1054
   ->  HashAggregate  (cost=640631.75..640631.80 rows=3 width=20) (actual time=11305.140..11305.142 rows=7 loops=1)
         Group Key: substr((customer.c_phone)::text, 1, 2)
         Buffers: shared hit=281850 read=44765 dirtied=94 written=10
         ->  Hash Anti Join  (cost=596632.29..640190.34 rows=58855 width=20) (actual time=10927.488..11284.467 rows=63744 loops=1)
               Hash Cond: (customer.c_custkey = orders.o_custkey)
               Buffers: shared hit=281850 read=44765 dirtied=94 written=10
               ->  Bitmap Heap Scan on customer  (cost=2912.59..41872.20 rows=140252 width=24) (actual time=836.360..1063.169 rows=191237 loops=1)
                     Recheck Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{20,30,27,17,21,15,16}'::text[])) AND (c_acctbal > $0))
                     Heap Blocks: exact=35188
                     Buffers: shared hit=35108 read=36970
                     ->  Bitmap Index Scan on customer_c_phone_idx  (cost=0.00..2877.52 rows=140252 width=0) (actual time=828.366..828.366 rows=191237 loops=1)
                           Index Cond: ((substr((c_phone)::text, 1, 2) = ANY ('{20,30,27,17,21,15,16}'::text[])) AND (c_acctbal > $0))
                           Buffers: shared hit=25 read=36865
               ->  Hash  (cost=405283.20..405283.20 rows=15074920 width=4) (actual time=9986.958..9986.958 rows=15000000 loops=1)
                     Buckets: 16777216  Batches: 1  Memory Usage: 658416kB
                     Buffers: shared hit=246739 read=7795 dirtied=94 written=10
                     ->  Seq Scan on orders  (cost=0.00..405283.20 rows=15074920 width=4) (actual time=0.021..4589.985 rows=15000000 loops=1)
                           Buffers: shared hit=246739 read=7795 dirtied=94 written=10
 Planning time: 2.868 ms
 Execution time: 11310.510 ms
(34 rows)

COMMIT;
COMMIT