How to check if enable/disable keys work?

问题

I have a table with an indexed varchar(256) column.

For faster bulk insert, I disabled keys, insert more than 10 million entries, and then re-enable the keys after insertion is done.

Surprisingly, the enable/disable keys took no time:

mysql> alter table xxx disable keys;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> alter table xxx enable keys;
Query OK, 0 rows affected, 1 warning (0.00 sec)

How do I ensure that enable/disable keys were working properly?

回答1:

As you guessed, InnoDB does not support DISABLE/ENABLE KEYS. The warning you got is:

code 1031 - Table storage engine for 'table_name' doesn't have this option

As you can see here. To see the warning yourself, run SHOW WARNINGS; after you run the ALTER.

回答2:

To check if your keys are enabled/disabled, run:

show keys in table_name

+----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+----------+---------------+
| Table    | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment  | Index_comment |
+----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+----------+---------------+
| table123 |          0 | PRIMARY  |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |          |               |
| table123 |          1 | id       |            1 | id          | A         |        NULL |     NULL | NULL   |      | BTREE      | disabled |               |
+----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+----------+---------------+

If the key is disabled, the Comment column will show disabled. If it's enabled, the column will be empty:

[Comment column shows] information about the index not described in its own column, such as disabled if the index is disabled. ➫➫➫

来源：https://stackoverflow.com/questions/4980917/how-to-check-if-enable-disable-keys-work