有没有什么工具可以做到这一点?你给它一个 SQL 查询,它会给出建议。例如,我正在尝试优化以下查询:
Load (383.2ms) SELECT COUNT(*) as plays, p.chosen_race as race, p.won as won, r.game_type as type FROM plays p, replays r WHERE p.replay_id = r.id AND r.is_public = 't' AND r.winner_known = 't' GROUP BY r.game_type, p.chosen_race, p.won ORDER BY r.game_type, p.chosen_race
解释
Aggregate (cost=8389.92..8389.93 rows=1 width=4)
-> Hash Left Join (cost=3570.69..8150.84 rows=95630 width=4)
Hash Cond: (replays.id = players_replays_join.replay_id)
-> Hash Left Join (cost=1785.34..3772.35 rows=38995 width=4)
Hash Cond: (replays.id = plays.replay_id)
-> Seq Scan on replays (cost=0.00..833.02 rows=15901 width=8)
Filter: (is_public AND ((state)::text = 'success'::text))
-> Hash (cost=1110.82..1110.82 rows=41082 width=4)
-> Seq Scan on plays (cost=0.00..1110.82 rows=41082 width=4)
-> Hash (cost=1110.82..1110.82 rows=41082 width=8)
-> Seq Scan on plays players_replays_join (cost=0.00..1110.82 rows=41082 width=8)
我们应该如何解释该输出?
最佳答案
您需要表格中的数据。
然后你可以使用EXPLAIN ANALYZE
http://www.postgresql.org/docs/9.0/interactive/using-explain.html
您可以添加和删除索引并比较时间。
关于database - 给定一个查询,您如何知道要添加哪些索引?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/6612789/