percona-toolkit之pt-index-usage和pt-duplicate-key-checker详解
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1>
pt-index-usage：从慢查询日志中读取查询并分析它们如何使用索引。 (用来查找不常使用索引)
./pt-index-usage --help
打印报告
./pt-index-usage /mysqldata/mysqlslowlog/slowquery.log -h192.168.226.131 -uroot -p6yhn^YHN -decology
[mysql@mysql bin]$ ./pt-index-usage /mysqldata/mysqlslowlog/slowquery.log -h192.168.226.131 -uroot -p6yhn^YHN
DBD::mysql::db selectall_arrayref failed: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘/‘ at line 1 [for Statement "EXPLAIN SELECT IFNULL(SUM(INDEX_LENGTH),0) from information_schema.TABLES where ENGINE=‘InnoDB‘ */"] at ./pt-index-usage line 4598, <> line 1.
DBD::mysql::db selectall_arrayref failed: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘/‘ at line 1 [for Statement "EXPLAIN SELECT IFNULL(SUM(DATA_LENGTH),0) from information_schema.TABLES where ENGINE=‘InnoDB‘ */"] at ./pt-index-usage line 4598, <> line 2.
DBD::mysql::db selectall_arrayref failed: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘/‘ at line 1 [for Statement "EXPLAIN SELECT COUNT(*) FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE=‘BASE TABLE‘ */"] at ./pt-index-usage line 4598, <> line 4.
ALTER TABLE `test1`.`user` DROP KEY `idx_1`; -- type:non-unique
2> pt-duplicate-key-checker检查数据库的重复索引
索引会更查询带来好处，但是过量的索引反而可能会使数据库的性能降低
./pt-duplicate-key-checker --help
1> 表结构
[root@localhost][test1]> show index from user;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| user | 0 | PRIMARY | 1 | id | A | 1042305 | NULL | NULL | | BTREE | | |
| user | 1 | idx_1 | 1 | id | A | 1042305 | NULL | NULL | | BTREE | | |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
字段id有两个索引，
[mysql@mysql bin]$ ./pt-duplicate-key-checker -uroot -p6yhn^YHN
# ########################################################################
# test1.user
# ########################################################################
# idx_1 is a duplicate of PRIMARY
# Key definitions:
# KEY `idx_1` (`id`)
# PRIMARY KEY (`id`),
# Column types:
# `id` int(11) not null auto_increment
# To remove this duplicate index, execute:
ALTER TABLE `test1`.`user` DROP INDEX `idx_1`;
# ########################################################################
# Summary of indexes
# ########################################################################
# Size Duplicate Indexes 4169220
# Total Duplicate Indexes 1
# Total Indexes 34
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