MySQL 5.1 or newer can sometimes start throwing a strange message into an error log. The message states that a query was unsafe for binary logging along with some additional information. What does it mean? Is it a problem?

From time to time you might spot MySQL error log filling with the following warning:

“[Warning] Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT. The statement is unsafe because it uses a LIMIT clause. This is unsafe because the set of rows included cannot be predicted. Statement: DELETE FROM score WHERE user_id = 12345 AND created = ’2012-04-15′ LIMIT 1″

If binary logging is enabled and the log format is set to STATEMENT, MySQL generates such message when it considers that a query is ambiguous and could behave differently each time it executes against the same data set. Such situation could happen, for example, on a …

Lets see what HA solutions can be designed in mysql and where are they suited.

1. Single master - single slave.

M(RW)|S(R) A simple master slave solution can be used for a small site - where all the inserts go into the master and some (non-critical) requests are served from the slave. In case if the master crashes, the slave can be simply promoted as the master - once it has replicated the "

The new MySQL 5.6 Development Milestone Release (DMR) includes many new enhancements. One of the most impressive is the use of Global Transaction Identifiers (GTIDs) for replication. With GTIDs enabled, administrators no longer need to keep track of binary log files and positions. In a nutshell, GTIDs simplify the setup and maintenance of replication.

MySQL Utilities has taken this a step further by providing two new utilities that automate two of the most complex replication administration tasks - switchover and failover. Switchover is changing the role of an active, healthy master to one of its slaves whereas failover is the act of promoting a candidate slave to become the new master. Clearly, switchover is an elective operation and failover is performed when there are issues with the master.

The GTID utilities are included in release-1.0.5 of MySQL Utilities. They are included as a plugin for MySQL Workbench or via …

As the Product Manager for the MySQL database it is always great to announce when the MySQL Engineering team delivers another great product release.  As a field DBA and developer it is even better when that release contains improvements and innovation that I know will help those currently using MySQL for apps that range from modest intranet sites to the most highly trafficked web sites on the web.  That said, it is my pleasure to take my hat off to MySQL Engineering for today's release of the MySQL 5.6.5 Development Milestone Release ("DMR"). The new highlighted features in MySQL 5.6.5 are discussed here:

New Self-Healing Replication Clusters
The 5.6.5 DMR improves MySQL Replication by adding Global Transaction Ids and automated utilities for self-healing Replication clusters.  Prior to 5.6.5 this has been somewhat of a pain point for MySQL users with most developing custom solutions or looking to costly, …

The objective of this benchmark is to measure the performance improvement achieved when enabling the Multi-Threaded Slave enhancement delivered as a part MySQL 5.6.

As the results demonstrate, Multi-Threaded Slaves delivers 5x higher replication performance based on a configuration with 10 databases/schemas. For real-world deployments, higher replication performance directly translates to:

· Improved consistency of reads from slaves (i.e. reduced risk of reading "stale" data)

· Reduced risk of data loss should the master fail before replicating all events in its binary log (binlog)

The multi-threaded slave splits processing between worker threads based on schema, allowing updates to be applied in parallel, rather than sequentially. This delivers benefits to those workloads that isolate application …

We are excited to announce TokuDB® v6.0, the latest version of Tokutek’s flagship storage engine for MySQL and MariaDB.

This version offers feature and performance enhancements over previous releases, support for XA (two-phase transactional commits), better compression, and reduced performance variability associated with checkpointing. This release also brings TokuDB support up to date on MySQL v5.1, MySQL v5.5 and MariaDB v5.2. There’s a lot of great technical stuff under the hood in this release and I’ll be reviewing the improvements one-by-one over the course of this week.

I’ll be posting more details about the new features and performance, so here’s an overview of what’s in store.

Replication Slave Lag

One of the things TokuDB does well is single-threaded insertions, which translates directly into less slave lag. With TokuDB v6.0, we introduce support for XA, which insures for …

MySQL community conferences are alive and well in 2012.   Percona has taken the initiative to host the yearly MySQL event at the Santa Clara Hyatt; it's now called Percona Live MySQL Conference and Expo.  It runs from 10 through 12 April.  But don't plan on going home Thursday night.  On Friday 13 April you can also attend the SkySQL and MariaDB MySQL Solutions Day in the same location.  And wait, that's not all!  Drizzle Day is also on 13 April and also at the Hyatt, so you can catch up on what the Drizzle folks have been up to for the last 12 months.

Now for some specifics on the conferences where Continuent will be appearing. …

tldr; A single MySQL Cluster prioritises Consistency in Network partition events. Asynchronously replicating MySQL Clusters prioritise Availability in Network partition events.

I was recently asked about the relationship between MySQL Cluster and the CAP theorem. The CAP theorem is often described as a pick two out of three problem, such as choosing from good, cheap, fast. You can have any two, but you can't have all three. For CAP the three qualities are 'Consistency', 'Availability' and 'Partition tolerance'. CAP states that in a system with data replicated over a network only two of these three qualities can be maintained at once, so which two does MySQL Cluster provide?

Standard 'my interpretation of CAP' section

Everyone who discusses CAP like to rehash it, and I'm no exception. …

When I joined Continuent, at the end of 2010, I was fascinated by the technology of its core products. Readers of this blog know that I have had my hands full with Tungsten Replicator, but what really turned me on was the flagship management suite, Tungsten Enterprise. After hammering at it for several months, and always marveling at the beauty of its technology, let me give a tour of the suite, so that you'll understand what's so exciting about it. First off, Tungsten Enterprise is not simply a replication tool. It is based on replication, but it is mostly a data management suite. Its aim is to reduce complexity for the user and to show a database cluster to the user as if it were a single server, always on, no matter what happens. The most amazing things that you will see in Tungsten Enterprise are

• Automatic failover
• Cluster console, and …

Tungsten Replicator 2.0.5 was released this week-end. The release notes have quite a long list of bug fixes. Thanks to all the ones who have submitted bug reports, and fixes! There are a couple of new features as well. The replicator includes now a slave prefetch service. Unlike parallel replication, this feature works fine with a single database, and provides performance improvements that in many cases solve the slave lagging problems. This was a bitch of a feature to get right. Many have tried it, many have experienced various degrees of success, and several failures. We started with the bold assertiveness of the brave after an exciting talk at Percona Live in October, and I was …