table ytt.girl1
column | type | modifiers
--------+---------+--------------------
id | integer | not null
rank | integer | not null default 0
indexes:
girl1_pkey primary key, btree (id)
idx_girl1_rank btree (rank) where rank >= 10 and rank
执行的查询语句为：
select * from girl1 where rank between 20 and 60 limit 20;
用了全部索引的查询计划：
query plan
---------------------------------------------------------------------------------------------------------------------------------
limit (cost=0.29..36.58 rows=20 width=8) (actual time=0.024..0.054 rows=20 loops=1)
-> index scan using idx_girl1_rank on girl1 (cost=0.29..421.26 rows=232 width=8) (actual time=0.023..0.044 rows=20 loops=1)
index cond: ((rank >= 20) and (rank
total runtime: 0.087 ms
(4 rows)
time: 1.881 ms
用了条件索引的查询计划：
query plan
---------------------------------------------------------------------------------------------------------------------------------
limit (cost=0.28..35.54 rows=20 width=8) (actual time=0.036..0.068 rows=20 loops=1)
-> index scan using idx_girl1_rank on girl1 (cost=0.28..513.44 rows=291 width=8) (actual time=0.033..0.061 rows=20 loops=1)
index cond: ((rank >= 20) and (rank
total runtime: 0.106 ms
(4 rows)
time: 0.846 ms
ytt>show create table girl1_filtered_index; +----------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | table | create table | +----------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | girl1_filtered_index | create table `girl1_filtered_index` ( `id` int(11) not null, `rank` int(11) not null default '0', primary key (`id`), key `idx_rank` (`rank`) ) engine=innodb default charset=latin1 | +----------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec) 接下来，对基础表的更新操作做下修改，创建了三个触发器。 delimiter $$ use `t_girl`$$ drop trigger /*!50032 if exists */ `filtered_insert`$$ create /*!50017 definer = 'root'@'localhost' */ trigger `filtered_insert` after insert on `girl1` for each row begin if new.rank between 10 and 100 then insert into girl1_filtered_index values (new.id,new.rank); end if; end; $$ delimiter ; delimiter $$ use `t_girl`$$ drop trigger /*!50032 if exists */ `filtered_update`$$ create /*!50017 definer = 'root'@'localhost' */ trigger `filtered_update` after update on `girl1` for each row begin if new.rank between 10 and 100 then replace girl1_filtered_index values (new.id,new.rank); else delete from girl1_filtered_index where id = old.id; end if; end; $$ delimiter ; delimiter $$ use `t_girl`$$ drop trigger /*!50032 if exists */ `filtered_delete`$$ create /*!50017 definer = 'root'@'localhost' */ trigger `filtered_delete` after delete on `girl1` for each row begin delete from girl1_filtered_index where id = old.id; end; $$ delimiter ; ok，，我们导入测试数据。 ytt>load data infile 'girl1.txt' into table girl1 fields terminated by ','; query ok, 100000 rows affected (1.05 sec) records: 100000 deleted: 0 skipped: 0 warnings: 0 ytt>select count(*) from girl1; +----------+ | count(*) | +----------+ | 100000 | +----------+ 1 row in set (0.04 sec) ytt>select count(*) from girl1_filtered_index; +----------+ | count(*) | +----------+ | 640 | +----------+ 1 row in set (0.00 sec)
select a.id,a.rank from girl1 as a where a.id in (select b.id from girl1_filtered_index as b where b.rank between 20 and 60) limit 20;