Question

How do we check Innodb plugin is installed or not in MySQL?
Is there any variable to check Innodb Plugin is installed or not?

Answer 1

If you need to determine whether or not InnoDB is enabled by querying the database, you should use the INFORMATION_SCHEMA tables.

SELECT SUPPORT FROM INFORMATION_SCHEMA.ENGINES WHERE ENGINE = 'InnoDB';

Which, if InnoDB is enabled and is the default database, gives a result of

+---------+
| SUPPORT |
+---------+
| DEFAULT |
+---------+

If InnoDB is available, but not the default engine, the result will be YES. If it’s not available, the result will obviously be NO.

Please see https://dev.mysql.com/doc/refman/8.0/en/information-schema-engines-table.html
and https://dev.mysql.com/doc/refman/8.0/en/information-schema.html for reference.

When InnoDB is available, the INFORMATION_SCHEMA tables you mentioned in a comment are also available.

SHOW TABLES FROM INFORMATION_SCHEMA LIKE 'INNODB%';

+----------------------------------------+
| Tables_in_INFORMATION_SCHEMA (INNODB%) |
+----------------------------------------+
| INNODB_CMP_RESET                       |
| INNODB_TRX                             |
| INNODB_CMPMEM_RESET                    |
| INNODB_LOCK_WAITS                      |
| INNODB_CMPMEM                          |
| INNODB_CMP                             |
| INNODB_LOCKS                           |
+----------------------------------------+