Оптимизация запроса postgres, которая выполняет сканирование seq

Question

У меня есть запрос, который занимает 7 секунд. Я пытаюсь его оптимизировать.

Это запрос:

explain analyze select count(*) from ab_view inner join ab_trial on (ab_view.trial_id = ab_trial.id) where ab_trial.variation_id = 339; 
                      QUERY PLAN                   
--------------------------------------------------------------------------------------------------------------------------------------------------------------- 
Aggregate (cost=91536.20..91536.21 rows=1 width=0) (actual time=6696.799..6696.800 rows=1 loops=1) 
    -> Hash Join (cost=15844.96..91068.32 rows=187155 width=0) (actual time=557.026..6695.972 rows=670 loops=1) 
     Hash Cond: (ab_view.trial_id = ab_trial.id) 
     -> Seq Scan on ab_view (cost=0.00..36588.46 rows=2368046 width=4) (actual time=0.028..2813.947 rows=2368125 loops=1) 
     -> Hash (cost=13743.40..13743.40 rows=128045 width=4) (actual time=516.418..516.418 rows=127671 loops=1) 
       Buckets: 4096 Batches: 8 Memory Usage: 572kB 
       -> Bitmap Heap Scan on ab_trial (cost=2868.84..13743.40 rows=128045 width=4) (actual time=21.722..302.626 rows=127671 loops=1) 
        Recheck Cond: (variation_id = 339) 
        -> Bitmap Index Scan on ab_trial_variation_id (cost=0.00..2836.82 rows=128045 width=0) (actual time=19.573..19.573 rows=127843 loops=1) 
          Index Cond: (variation_id = 339) 
Total runtime: 6697.140 ms 
(11 rows) 

И тезисы определения таблицы:

         Table "public.ab_view" 
    Column |   Type   |      Modifiers      
----------+--------------------------+------------------------------------------------------ 
id  | integer     | not null default nextval('ab_view_id_seq'::regclass) 
trial_id | integer     | not null 
datetime | timestamp with time zone | not null 
Indexes: 
    "ab_view_pkey" PRIMARY KEY, btree (id) 
    "ab_view_trial_id_126817c891814cd7_uniq" UNIQUE CONSTRAINT, btree (trial_id, datetime) 
    "ab_view_trial_id" btree (trial_id) 
Foreign-key constraints: 
    "trial_id_refs_id_6ea6b4c9" FOREIGN KEY (trial_id) REFERENCES ab_trial(id) DEFERRABLE INITIALLY DEFERRED 

             Table "public.ab_trial" 
    Column  | Type |      Modifiers      | Storage | Description 
---------------+---------+-------------------------------------------------------+---------+------------- 
id   | integer | not null default nextval('ab_trial_id_seq'::regclass) | plain | 
variation_id | integer | not null            | plain | 
experiment_id | integer | not null            | plain | 
device_id  | integer | not null            | plain | 
Indexes: 
    "ab_trial_pkey" PRIMARY KEY, btree (id) 
    "ab_trial_device_id_9594421392f2789_uniq" UNIQUE CONSTRAINT, btree (device_id, experiment_id) 
    "ab_trial_experiment_id" btree (experiment_id) 
    "ab_trial_temp_device_id" btree (device_id) 
    "ab_trial_variation_id" btree (variation_id) 
Foreign-key constraints: 
    "device_id_refs_id_050eed1f" FOREIGN KEY (device_id) REFERENCES ab_device(id) DEFERRABLE INITIALLY DEFERRED 
    "experiment_id_refs_id_ca7ef8d2" FOREIGN KEY (experiment_id) REFERENCES ab_experiment(id) DEFERRABLE INITIALLY DEFERRED 
    "variation_id_refs_id_909abcec" FOREIGN KEY (variation_id) REFERENCES ab_variation(id) DEFERRABLE INITIALLY DEFERRED 
Referenced by: 
    TABLE "ab_view" CONSTRAINT "trial_id_refs_id_6ea6b4c9" FOREIGN KEY (trial_id) REFERENCES ab_trial(id) DEFERRABLE INITIALLY DEFERRED 
    TABLE "ab_conversion" CONSTRAINT "trial_id_refs_id_bf42f054" FOREIGN KEY (trial_id) REFERENCES ab_trial(id) DEFERRABLE INITIALLY DEFERRED 
Has OIDs: no 

Я не знаю, как я могу оптимизировать его. Я запускаю Postgres 9.1. Я видел, что «счет» медленнее на 9.1, но я не уверен, что это моя проблема.

Answer 1

Определение таблицы нет, но похоже, что ab_view не имеет индекса на пробной версии.