MySQL/ MariaDB Schema Size

MySQL/ MariaDB Schema Size

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Create a MySQL or MariaDB view to show the aggregated size of each schema in the database:

See database size for more information.

CREATE  OR REPLACE VIEW schema_size AS
SELECT   table_schema
,        round(SUM(((data_length + index_length) / 1024 / 1024)), 2) table_size_mb
FROM     information_schema.tables  
WHERE table_schema IN ('dv', 'da', 'hue')  
GROUP BY table_schema
ORDER BY table_size_mb DESC

How to Clear the Slow Query Log on AWS RDS MySQL/ MariaDB

Category : How-to

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Here is a super simple little tip for clearing the mysql.slow_log in MySQL or MariaDB when running an RDS on Amazon AWS. 

For more information on AWS RDS, please see: https://aws.amazon.com/codedeploy/

Unfortunately the usual approach of simply DELETing or TRUNCATING data from the table doesn’t work due to a permission error. This is true, even for the AWS created master database user.

Error Code: 1044. Access denied for user 'masteruser'@'%' to database 'mysql'

Luckily, the Amazon AWS team have put together a package that clears out the table for us. 

CALL mysql.rds_rotate_slow_log;

EXECUTE IMMEDIATE MySQL

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Unlike recent versions of Maria DB, MySQL does not currently support the command EXECUTE IMMEDIATE.

Essentially EXECUTE IMMEDIATE is shorthand for perparing a statement, executing a statement and then finally deallocating the prepaired statement.

To get round this limitation in MySQL you can create a stored procedure that wraps up the commands required to execute a statement into a procedure so that you can call it as a one-liner.

CREATE PROCEDURE execute_immediate(IN query MEDIUMTEXT)
	MODIFIES SQL DATA
	SQL SECURITY DEFINER
BEGIN
	SET @q = query;
	PREPARE stmt FROM @q;
	EXECUTE stmt;
	DEALLOCATE PREPARE stmt;
END

You can then call the procedure as a one-liner like this:

CALL execute_immediate('QUERY GOES HERE');

Change Listening Port of MySQL or MariaDB Server

Category : How-to

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mysql-logoThe MySQL and MariaDB server both use a file called my.cnf for parameters that are used to configure the server. This is where the port number and, if you use it, the local socket can be configured. The default port number for both MySQL and MariaDB is 3306 but you can change it as required.

A local socket is the prefered method of connecting to a database as it removes much of the overhead of creating a TCP connection and transferring data. This comes with the limitation that it can only be used if the application accessing the database is on the same machine. In larger or highly available systems this may not be possible.

A TCP connection is the only option of connecting to your MySQL or MariaDB database from a remote machine. It incurs a small penalty over a local socket and therefore slightly higher latencies. MySQL server and MariaDB can be configured to use a local socket, TCP connections or both.

We’ll be editing the my.cnf file for the following sections. Open the file in your favourite editor.

vi /etc/mysql/my.cnf

Configuring local socket use

The socket option indicates the filesystem path to the location of the socket you’d like to use. Specify a filesystem path, usually /var/run/mysql/mysqld.sock and the socket will be created when the server next starts. Remove or comment (#) the line to disable socket access.

socket = /var/run/mysqld/mysqld.sock

Restart the server for the changes to take effect.

service mysql restart

Setting or changing the TCP port

The port option sets the MySQL or MariaDB server port number that will be used when listening for TCP/ IP connections. The default port number is 3306 but you can change it as required. Use the port option with the bind option to control the interface where the port will be listening. Use 0.0.0.0 to listen on all IP addresses on the host, or specify a single one directly to listen on a single interface. Omit both of these options to disable TCP/ IP connections.

port = 1234
bind = 10.10.10.10

Restart the server for the changes to take effect.

service mysql restart

Reset The root MYSQL/ MariaDB Password

Category : How-to

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mysql-logoIf you’ve lost or forgotten the root user password on a MySQL or MariaDB server you’ll want to reset it and leave all the other accounts and data intact. Fortunately it’s possible, but you’ll need access to an SSH account hosting the instance and the ability to stop and start the database service.

Before going any further, make sure your instance of MySQL or MariaDB is shutdown.

service mysql stop

Start the server in safe mode and don’t load the table grants and permissions.

mysqld_safe --skip-grant-tables &

Log into the local instance with the root user.

mysql -u root mysql

Run the below commands SQL, once connected, and reset your password. Be sure to substitute new-password with the new password for your root account.

use mysql;
UPDATE mysql.user SET Password=PASSWORD('new-password') WHERE User='root';
FLUSH PRIVILEGES;
exit;

Finally, start the SQL server instance and use your new root account password.

service mysql restart
mysql -u root -p

 


MySQL Database Alternative

Category : How-to

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mysql-logoThere are many alternatives to MySQL that tick some of the boxes you may require. There are plenty of free, open source databases such as PostgreSQL, MogoDB, CouchDB and Apache Derby however many of these databases have a different feature set or are a completely different type of database to the standard MySQL relational data model. Another question is what if I already have MySQL set up in my environment and would like to change? Many people are concerned that the (fairly) recent takeover of Sun Microsystems by Oracle could spell trouble for MySQL.

mariadb-logoMariaDB was created by some of the original developers of MySQL and was created by forking the MySQL code base. It[‘s maintained by the MariaDB Foundation who ensures the free availability of the database software. There are currently 2 main versions of MariaDB available as stable distributions:

  • Version 5.x – which is a drop in replacement for any version 5.x of MSSQL and promises to support all MySQL version 5.x functionality. With this version of MariaDB you can switch your applications to point at it and they will just work. All the connectors and client binaries are compatible and for most scenarios will work right out of the box.
  • Version 10.x – this is the new branch of MariaDB which drifts away from the original MySQL specification and introduces new features. Currently, most of the basics will work, but it no longer guarantees backwards compatibility with MySQL and can no longer be used as a drop in replacement. Eventually this had to happen to enable the MariaDB developers to implement the features they needed to and is the branch of MariaDB that’s being most actively developed.

As you can see, version 5.x is a version you can use straight away if you’re a MySQL 5.x user if you so choose. Version 10.x however, will take a little more time to implement as you’ll need to change the connectors in your applications and ensure that all the features you require from the database are the same. You may also wish to use some of Version 10.x’s features that would otherwise be unavailable.

Take a look at installing MariaDB on Ubuntu or installing a quick and easy database cluster.

 


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