For MyISAM one of the most important variables is the Key Buffer.  The Key Buffer is sometimes called the Key Cache. It's used as a buffer for the indices of MyISAM tables. There is some overhead in the buffer depending on the configured key block size. The official way to calculate the key buffer usage as documented in the MySQL Reference manual: 1 - ((Key_blocks_unused * key_cache_block_size) / key_buffer_size)  This will return the factor, so you have to multiply it with 100 to get the percentage. The Key_blocks_unused is used instead of the more obvious Key_blocks_used. This is due to the fact that Key_blocks_used is the maximum number of key blocks ever used. It will not return to 0 after a FLUSH TABLES. This calculation does not take the overhead in account. The key buffer efficiency can be calculated if the key buffer is empty or (has been) completely full. If the the key buffer is full: key_buffer_coefficient = key_cache_block_size/(key_buffer_size/Key_block...

Use DNS directly from your database mysql> SELECT lookup('localhost'); +---------------------+ | lookup('localhost') | +---------------------+ | 127.0.0.1 | +---------------------+ 1 row in set (0.00 sec) mysql> SELECT reverse_lookup('127.0.0.1'); +-----------------------------+ | reverse_lookup('127.0.0.1') | +-----------------------------+ | localhost | +-----------------------------+ 1 row in set (0.00 sec) This is how you install these functions. Build udf_example.so which is in your mysql source. ( make udf_example.so ) Copy the udf_example.so file from your build directory to your plugin_dir. Create the lookup and reverse_lookup functions mysql> CREATE FUNCTION lookup RETURNS STRING SONAME 'udf_example.so'; Query OK, 0 rows affected (0.00 sec) mysql> CREATE FUNCTION reverse_lookup RETURNS STRING SONAME 'udf_example.so'; Query OK, 0 rows affected (0.00 sec) I've created a feature ...

For MySQL it's a best practice to store IP addresses in a INT column rather than in a VARCHAR. This allows for more compact storage. This best practice is only for MySQL as PostgreSQL does have data types like inet and cidr . MySQL is equiped with the INET_ATON() and INET_NTOA() functions since version 3.23.15. In MySQL 5.6.3 the INET6_ATON() and INET6_NTOA() functions were addes to finaly add IPv6 address support. To make it easier to work with IPv4 and IPv6 addresses the IS_IPV4_COMPAT(), IS_IPV4_MAPPED(), IS_IPV4() and IS_IPV6() functions were added. The difference between the new and old functions is that the old functions use INT UNSIGNED to store IP addresses and the new function uses VARBINARY(16) for IPv6 addresses and VARBINARY(4) for IPv4 addresses. Here are some examples about how you could do nifty things with IP addresses in MySQL. Store hosts and networks in MySQL CREATE TABLE `hosts` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `hostname` varchar(255) DEFA...

This is a response on MySQL security: inconsistencies and Less known facts about MySQL user grants . As far as I know the privilege to grant PROXY privileges is also not very well understood. I blogged about that some time ago. In addion to the already highlighted issues with GRANT replication and grants can very well create an unwanted situation: master> SHOW GRANTS FOR 'user'@'host'\G *************************** 1. row *************************** Grants for user@host: GRANT USAGE ON *.* TO 'user'@'host' IDENTIFIED BY PASSWORD '*4994A78AFED55B0F529C11C436F85458C1F8D4C2' *************************** 2. row *************************** Grants for user@host: GRANT SELECT, INSERT, UPDATE, DELETE ON `somedb`.* TO 'user'@'host' 2 rows in set (0.00 sec) master> GRANT SELECT,INSERT,UPDATE,DELETE ON anotherdb.* TO 'user'@'host'; Query OK, 0 rows affected (0.00 sec) master> SHOW GRANTS FOR 'user'@'host...

This is a reply on Regularly flushing the MySQL Query Cache . The original acticle is about regulary flushing the MySQL Query Cache as it will fragment over time. There are some drawbacks for the cron method for flushing the query cache: It will only work on UNIX like platforms as MS Windows uses the task scheduler to schedule tasks. It needs credentials to login to the database. It's not included in your database backup There is another method, which is native to MySQL: the event scheduler . Step 1: Enable the event scheduler: mysql> SET GLOBAL event_scheduler=ON; Query OK, 0 rows affected (0.00 sec) And don't forget to set/change this in your my.cnf or my.ini Step 2: Create the event: mysql> CREATE EVENT flush_query_cache ON SCHEDULE EVERY 1 HOUR DO FLUSH QUERY CACHE; Query OK, 0 rows affected (0.00 sec) mysql> SHOW EVENTS\G *************************** 1. row *************************** Db: test Name: flush_query_cache Definer: msandbox@localhos...

What will be first? The new and updated MySQL certification or the new OSS-DB exam which is announced by LPI in Japan? The OSS-DB is only for PostgreSQL for now, but will cover more opensource databases in the future. There seem to be two levels: Silver: Management consulting engineers who can improve large-scale database Gold: Engineers who can design, development, implementation and operation of the database The google translate version can be found here . I found this info on Tatsuo Ishii's blog

This is a reply on A bit on SANs and system dependencies by Eric Bergen. Lets first start by making a difference between entry level, midrange and high-end SAN's. Entry level: This is basically a bunch of disks with a network connection. The Oracle/Sun/StorageTek 2540 is an example for this category. This storage is aimed at lowcost shared storage. Midrange: This kind of storage generally features replication and more disks than entry level. HP EVA is what comes to mind for this category. This storage is aimed at a good price/performance. High-End: This is mainframe style storage which is made usable for open systems. Hitachi Data Systems VSP is a good example of this category. This category is for extreme performance and reliability. Please make sure to not (mis-)judge High-End SAN by the experiences you had with entry-level storage. Why should we use SAN/NAS storage? SAN's can offer more reliable storage than local storage SAN's offer all kinds of extra services like re...