Galera Cluster Enterprise Edition (EE) has had support for Non-Blocking Operations (NBO) schema upgradesever since the first release of Galera Cluster Enterprise Edition (EE). It is reasonably well documented, and we think more people will benefit from using it, of course. Schema changes tend to always remain a daunting task when you have large databases to manage.

To compare between Total Order Isolation (TOI), the default, with NBO that is available in Galera Cluster Enterprise Edition (EE), we create a test table:

CREATE TABLE large;
USE large;

CREATE TABLE test_table (
    id INT PRIMARY KEY AUTO_INCREMENT,
    data VARCHAR(255),
    num1 INT,
    num2 INT,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

Then we …

Background The Skinny

Performing schema changes often requires extended downtime for applications. This is due to MySQL needing to rebuild tables for common schema change operations. Tools like pt-online-schema-change have been written to try to overcome the downtime associated with schema changes, however they are complex and put a high load on the database. Amazon’s Aurora improves some schema changes operations, but still requires a table rebuild for common operations like adding a column using before or after, or simply to add a column with a default value. Rebuilding a table with millions of rows can take hours and prevent writes to that table the entire time.

How Can Tungsten Clustering Keep Applications Running? How Does It All Work?

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December 10, 2013 By Severalnines

As a follow-up to the Webinar on Zero Downtime Schema Changes in Galera Cluster, we’ll now walk you through the detailed steps on how to update your schema. The two methods (TOI and RSU) have both their pros and cons, and given parameters like table size, indexes, key_buffer_size, disk speed, etc., it is possible to estimate the time taken for the schema to be upgraded. Also, please note that a schema change is non-transactional so it would not be possible to rollback the DDL if it fails midway. Therefore, it is always recommended to test the schema changes and ensure you have recoverable backups before performing this on your production clusters. 

This post examines the way DDL changes are propagated in Galera, and outlines the steps to upgrade the …

November 14, 2013 By Severalnines

Database schema changes are usually not popular among DBAs or sysadmins, not when you are operating a cluster and cannot afford to switch off the service during a maintenance window. There are different ways to perform schema changes, some procedures being more complicated than others. We invited Seppo from the Codership team to tell us about the options. If you’d like to learn more, please register for our new webinar.

Webinar: Galera Cluster Best Practices - Zero Downtime Schema Changes

Tuesday, December 3rd 2013

Register now - Europe/MEA/APAC

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