Pat Maddox wrote:
Here's my SQL query. I don't think it's too gigantic, but it is kind
of beastly:
SELECT COUNT(r) FROM trainer_hand_results r, trainer_scenarios s,
trainer_scenario_stats stats WHERE r.user_id=1 AND
r.trainer_scenario_id=s.id AND s.id=stats.trainer_scenario_id AND
r.action=stats.correct_action;
When I EXPLAIN it, I get:
Aggregate (cost=18.12..18.13 rows=1 width=32)
-> Nested Loop (cost=0.00..18.12 rows=1 width=32)
-> Nested Loop (cost=0.00..12.28 rows=1 width=40)
Join Filter: (("outer"."action")::text =
("inner".correct_action)::text)
-> Seq Scan on trainer_hand_results r
(cost=0.00..6.56 rows=1 width=181)
Filter: (user_id = 1)
-> Index Scan using
trainer_scenario_stats_trainer_scenario_id_index on
trainer_scenario_stats stats (cost=0.00..5.71 rows=1 width=149)
Index Cond: (stats.trainer_scenario_id =
"outer".trainer_scenario_id)
-> Index Scan using trainer_scenarios_pkey on
trainer_scenarios s (cost=0.00..5.82 rows=1 width=4)
Index Cond: ("outer".trainer_scenario_id = s.id)
(10 rows)
I don't have a lot of experience with getting queries to go faster.
The things that jump out at me though are two nested loops and a
sequential scan. What could I do to speed this up?
Have you analyzed the tables in question?
Post the result of 'explain analyze' rather than just explain.
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