Thanks to all who attended my webinar yesterday.  The slides and recording are available on the webinar’s page.  I was a bit overwhelmed with the amount of questions that came in and I’ll try to answer them the best I can here.

Q: Does Percona XtraDB Cluster support writing to multiple master?

Yes, it does.  However, locks are not held on all nodes while a transaction is in progress, so there is a possibility for conflicts between simultaneous writes on different nodes.  Certification is the process that Galera uses to protect your data integrity, and the problem is pushed back to the application to handle in the form of deadlock errors.   As long as you understand this and the conditions where you may see more deadlocks (and your application can properly handle them), multi-node …

MySQL Utilities is one of those gems that every MySQL user should know about. They simplify and help automate a wide range of tasks and activities that everyone from casual users to seasoned DBAs may need to carry out on their MySQL setup from time to time, all the way from cloning users, copying databases […]

My students required way to remove all their tables, views, and constraints from a MySQL database (or the alias schema). Since they’re using referential or foreign key constraints, I also wrote one procedure to drop all foreign key constraints from a database. There’s also another to drop views. The final stored procedure calls the procedure that drops foreign keys, then calls the procedure to drop views before dropping all the tables.

Here’s the dropForeignKeys stored procedure:

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-- Provide a log file debugging statement.
SELECT 'DROP PROCEDURE IF EXISTS dropForeignKeys';
 
-- Conditionally drop the procedure.
DROP PROCEDURE IF EXISTS …

This is a continuation of my post on migration-of-mtr-suites-to-use-innodb . To set the context here is a quick recap.

MySQL 5.5 had the following changes with respect to the default engine

• Default engine in the server changed from MyISAM to InnoDB
• MTR modified to start server with the old default MyISAM. (This was required because historically most test results were recorded with MyISAM and many of them would fail if tests were run with the new server default,  InnoDB)
• Tests retained as is in 5.5 and planned to migrate them to run with default engine in a future release

In MySQL 5.7 release we have started the migration project. Right in the beginning we realized that the switch of default engine had an unexpected side effect. MTR tests that were developed post 5.5 were also getting …

Galera cluster uses Galera library  for the replication implementation. To interface with Galera replication, Codership has enhanced MySQL server to support replication API definition in the wsrep API project. The implementation of the replication API in MySQL server, happens in open source project: MySQL-wsrep.

In this Galera Cluster setup, I have taken 3 nodes to illustrate.

node1(centos2) - 192.168.56.112
node2(centos3) - 192.168.56.113
node3(centos4) - 192.168.56.114

Packages Required.

1 galera-25.3.2-1.rhel6.x86_64.rpm                      ( …

MariaDB 5.5.35 was recently released (it is the latest MariaDB 5.5), and is available for download here:

https://downloads.mariadb.org/mariadb/5.5.35/

This is a maintenance release, and so there are not too many big changes of note. However, there are a couple items worth mentioning:

1. Includes all bugfixes and updates from: MySQL 5.5.35
2. Includes all bugfixes and updates from: XtraDB from Percona-Server-5.5.35-rel33.0

read more

In teaching, I had a problem because my students have different base operating systems, like Windows 7, Windows 8, Linux, and Mac OS X. I needed a teaching and lecture platform that would let me teach it all (not to mention support their environments). That meant it had to virtualize any of the following with a portable device:

• Windows 7 or 8 hosting natively an Oracle Database 11g XE, 11g, or 12c and MySQL Database 5.6
• Windows 7 or 8 hosting a Fedora or Oracle Unbreakable Linux VM (3 or 4 GB) with Oracle Database 11g XE, 11g, or 12c and MySQL Database 5.6
• Mac OS X hosting a Fedora or Oracle Unbreakable Linux VM (3 or 4 GB) with Oracle Database 11g XE, 11g, or 12c and MySQL Database 5.6
• Ubuntu hosting a Fedora or Oracle Unbreakable Linux VM (3 or 4 GB) with Oracle Database 11g XE, 11g, or …

I’ve continued building on my MariaDB GIS and node.js example application that I wrote about two weeks back, https://blog.mariadb.org/node-js-mariadb-and-gis/. The application shows how to load GPX information into MariaDB, using some MariaDB GIS functionality, and making use of the node.js platform together with MariaDB’s non-blocking client.

With the GPX data converted into GIS points in the MariaDB database, I wanted to further expand a little on both the GIS aspect and also look at how some additional data could be shown in the application by using jQuery’s Ajax calls to update a piece of the web based application UI.

To start with, an interesting thing to do when you have a bunch of GIS points in a …

In MySQL, filesort is the catch-all algorithm for producing sorted results for ORDER-BY or GROUP-BY queries. MySQL has two algorithms for filesort, both the original and the modified algorithms are described in the user manual.  The most commonly used algorithm is the so called modified algorithm, it is used for all cases except when BLOB and TEXT column are involved.

In 5.7.3, Tor Didriksen in the optimizer team introduced one more optimization that applies to the modified algorithm.  Let us first take a look at how MySQL´s modified filesort algorithm worked up to 5.7.2.

1. Read the rows that match the WHERE clause.
2. For each row, record a tuple of values consisting of the sort key value and the additional fields referenced by the query.
3. When the sort buffer becomes full, sort the tuples …

In addition to my recent post, I just had to go into using the –use-tts for specific tables and selective backup sets.

As all my schemas were employeesn, I thought it would be a good idea to run:

mysqlbackup -uroot --socket=/tmp/mysql.sock --backup-dir=/home/mysql/MEB/restore \
--with-timestamp --use-tts --include=employees* backup

as I want all the tables. If I only wanted a specific table, say ‘salaries’ I could have done:

mysqlbackup -uroot --socket=/tmp/mysql.sock --backup-dir=/home/mysql/MEB/restore \
--with-timestamp --use-tts --include=employees*\.*salaries backup

and backup just the ‘salaries’ tables but from all the employeesn databases.

then.. be a mean little dba:

drop database employees;
drop database employees10;
drop database employees11;
..
..
drop database employees2;
drop database employees20;
drop database …