new_query.sql

explain analyse
select sum(pv), country FROM (
  select sum(pv) as pv, country
  from events_2015_09_01
  group by country
  UNION ALL
  select sum(pv) as pv, country
  from events_2015_09_02
  group by country
  UNION ALL
  select sum(pv) as pv, country
  from events_2015_09_03
  group by country
  ) AS merged_days
group by country
order by sum(pv) desc;

Sort  (cost=510008.93..510009.43 rows=200 width=17) (actual time=9256.076..9256.085 rows=216 loops=1)
  Sort Key: (sum("*SELECT* 1".pv)) DESC
  Sort Method: quicksort  Memory: 36kB
  ->  HashAggregate  (cost=509998.78..510001.28 rows=200 width=17) (actual time=9255.889..9255.954 rows=216 loops=1)
        Group Key: "*SELECT* 1".country
        ->  Append  (cost=18582.28..509986.38 rows=2481 width=17) (actual time=320.171..9253.958 rows=4252 loops=1)
              ->  Subquery Scan on "*SELECT* 1"  (cost=18582.28..18583.86 rows=79 width=16) (actual time=320.169..320.221 rows=144 loops=1)
                    ->  HashAggregate  (cost=18582.28..18583.07 rows=79 width=12) (actual time=320.168..320.196 rows=144 loops=1)
                          Group Key: events_2015_09_01.country
                          ->  Seq Scan on events_2015_09_01  (cost=0.00..16098.52 rows=496752 width=12) (actual time=0.012..68.434 rows=496752 loops=1)
              ->  Subquery Scan on "*SELECT* 2"  (cost=17897.01..17898.67 rows=83 width=16) (actual time=324.356..324.420 rows=144 loops=1)
                    ->  HashAggregate  (cost=17897.01..17897.84 rows=83 width=12) (actual time=324.353..324.392 rows=144 loops=1)
                          Group Key: events_2015_09_02.country
                          ->  Seq Scan on events_2015_09_02  (cost=0.00..15500.67 rows=479267 width=12) (actual time=0.026..85.460 rows=479267 loops=1)
              ->  Subquery Scan on "*SELECT* 3"  (cost=17721.11..17722.83 rows=86 width=16) (actual time=315.809..315.873 rows=144 loops=1)
                    ->  HashAggregate  (cost=17721.11..17721.97 rows=86 width=12) (actual time=315.808..315.854 rows=144 loops=1)
                          Group Key: events_2015_09_03.country
                          ->  Seq Scan on events_2015_09_03  (cost=0.00..15356.74 rows=472874 width=12) (actual time=0.010..84.895 rows=472874 loops=1)
              ->  Subquery Scan on "*SELECT* 4"  (cost=15982.97..15984.49 rows=76 width=17) (actual time=289.241..289.293 rows=137 loops=1)
                    ->  HashAggregate  (cost=15982.97..15983.73 rows=76 width=13) (actual time=289.239..289.277 rows=137 loops=1)
                          Group Key: events_2015_09_04.country
                          ->  Seq Scan on events_2015_09_04  (cost=0.00..13846.98 rows=427198 width=13) (actual time=0.011..77.566 rows=427198 loops=1)
              ->  Subquery Scan on "*SELECT* 5"  (cost=15006.29..15007.95 rows=83 width=17) (actual time=272.963..273.016 rows=139 loops=1)
                    ->  HashAggregate  (cost=15006.29..15007.12 rows=83 width=13) (actual time=272.961..272.999 rows=139 loops=1)
                          Group Key: events_2015_09_05.country
                          ->  Seq Scan on events_2015_09_05  (cost=0.00..13006.86 rows=399886 width=13) (actual time=0.011..73.353 rows=399886 loops=1)
              ->  Subquery Scan on "*SELECT* 29"  (cost=18205.22..18207.00 rows=89 width=16) (actual time=332.204..332.274 rows=150 loops=1)
                    ->  HashAggregate  (cost=18205.22..18206.11 rows=89 width=12) (actual time=332.203..332.251 rows=150 loops=1)
                          Group Key: events_2015_09_30.country
                          ->  Seq Scan on events_2015_09_30  (cost=0.00..15759.15 rows=489215 width=12) (actual time=0.014..91.622 rows=489215 loops=1)
Planning time: 0.929 ms
Execution time: 9256.820 ms