InnoDB will notice circular dependencies and return an error instantly, to prevent deadlocks.
In InnoDB, secondary indexes contain primary key values. So if your primary key is large, other indexes will also be large.
Very active swapping can cause the entire operating system to become unresponsive, to the point that you can’t even log in and kill the MySQL process. We recommend you run your databases without using swap space at all.
If you set a variable’s global value whole the server is running, the values for the current session and any other existing sessions are not affected. Keep this in kind if your clients rely on persistent connections. This is because the session values are initialized from the global value when the connections are created.
Mysql8.0 introduced a new feature called persisted system variables which allows you to set the value once for runtime and MySQL will write this setting out to disk, enabling it to be used at the next start.
In MySQL8.0, a new configuration option, innodb_dedicated_server, was introduced. This option examines the available memory on the server abd configures four additional variables:
innodb_buffer_pool_size
inmodb_log_file_size
innodb_log_files_in_group
innodb_flush_method
The InnoDB buffer pool needs more memory than anything else, as it is generally the most important variable for performance.
