Gary Pendergast

Tag: MySQL

  • The \G modifier in the MySQL command line client

    A little publicized, but exceedingly useful feature of the MySQL command line client is the \G modifier. It formats the query output nicely, so you can read through it easier. To use it, you just replace the semi-colon at the end of the query with ‘\G’. For example, checking the master status: mysql> SHOW MASTER…

  • Upgrading MySQL with minimal downtime through Replication

    Problem With the release of MySQL 5.1, many DBAs are going to be scheduling downtime to upgrade their MySQL Server. As with all upgrades between major version numbers, it requires one of two upgrade paths: Dump/reload: The safest method of upgrading, but it takes out your server for quite some time, especially if you have…

  • Permissions by interface on the local server

    I had an issue come up recently that involved some confusion over permissions for the same user, connecting through different interfaces. For example, say you have a server with the public IP address of 192.168.0.1. You could connect to it from the local machine using the following commands: shell> mysql -h localhost # Connects through…

  • Replication Checksumming Through Encryption

    Problem A problem we occasionally see is Relay Log corruption, which is most frequently caused by network errors. At this point in time, the replication IO thread does not perform checksumming on incoming data (currently scheduled for MySQL 6.x). In the mean time, we have a relatively easy workaround: encrypt the replication connection. Because of…

  • Case Insensitive REPLACE() for MySQL

    One request I occasionally see is for a case insensitive version of REPLACE() for MySQL. I wrote this a while back, but here it is now for all of you to play around with. It uses a basic naïve string search algorithm, so can be slow under some circumstances. [code lang=”sql”]DELIMITER $$ DROP FUNCTION IF…

  • Replication with InnoDB and MyISAM Transactions

    There’s a change of behaviour in MySQL 5.1.31 for Row Based Replication, if you have InnoDB transactions that also write to a MyISAM (or other non-transactional engine) table. It’s a side effect of fixing Bug #40116. Take this simple example: Transaction 1: INSERT INTO myisam_tbl (item, val) VALUES (1, 0); Transaction 1: INSERT INTO innodb_tbl…