Pt-duplicate-key-checker Check the database for duplicate indexes

Pt-duplicate-key-checker is also a very useful tool in Percona-toolkit to help you detect duplicate indexes or primary keys in a table. We know that indexes can be more useful than queries, but too much indexing can degrade the performance of the database, and this tool can help us find duplicate indexes and give you suggestions for deleting duplicate indexes.

First look at the index structure of my table
Mysql> show indexes from Curs;
[SQL]  View Plain  copy +-------+------------+----------+--------------+-------------+-----------+----------- --+----------+--------+------+------------+---------+---------------+   | table | non_ unique | key_name | seq_in_index | column_name | collation |  Cardinality | Sub_part | Packed | Null | Index_type |  comment | index_comment |   +-------+------------+----------+--------------+---------- ---+-----------+-------------+----------+--------+------+------------+---------+---------------+   |  curs  |          0 | PRIMARY   |            1 | id           | A          |           1 |     null |  null   |      | btree      |          |                |   | curs  |           1 | name     |             1 | name        | a          |            1 |     NULL | NULL   |       | BTREE      |          |               |   | curs   |          1 | age       |            1 | age          | A          |           1 |      NULL | NULL   |      | BTREE       |         |                |   | curs  |           1 | name_age |             1 | name        | a          |           1  |     null | null   |      |  BTREE      |         |                |   | curs   |          1 | name_age |             2 | age          | A         |            1 |     NULL |  Null   |      | btree      |          |                |   | curs  |          1  | age_name |            1 |  age         | A          |           1 |      null | null   |      | btree       |         |                |   | curs  |           1 | age_name |             2 | name        | A          |           1  |     NULL | NULL   |       | btree      |         |                |   |  curs  |          1 | name_1    |            1 | name         | A         |            1 |     null | null    |      | BTREE      |          |                |   | curs  |           1 | age_1    |             1 | age         | A          |           1  |     null | null   |      |  BTREE      |         |                |   +-------+------------+------ ----+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+- --------------+  
There are a lot of duplicate indexes, such as name and Name_age repetition, and Name_1 Repeat, these 3 indexes are the same index. See below how to use/usr/local/bin/pt-duplicate-key-checker to check for duplicate indexes.

[Root@localhost ~]#/usr/local/bin/pt-duplicate-key-checker--host=192.168.1.106--user= ' mysql '--password= ' 123456 ' --databases=test--tables=curs
[SQL]  View Plain  copy # ########################################################################    # test.curs                                                                     # ############# ###########################################################      # name is a  left-prefix of name_age   # key definitions:   #    key  ' name '   (' name '),   #   key  ' name_age '   (' name ', ' age '),    # column types:   #          ' name '   varchar (1)  not null default  '    #          ' Age '  smallint (3)  unsigned not null default  ' 0 '    #