As the need for information grows so does the size of data we need to keep in our databases. SST is unavoidable for spinning up new nodes in a PXC cluster and when datasets reach the “terra-byte” range this becomes ever more cumbersome requiring many hours for a new node to synchronize.

More often that not, it is necessary to implement custom “wsrep_sst” scripts or resort to manual synchronization processes. Luckily cloud providers provide convenient methods to leverage disk snapshots that can be used to quickly transfer data between nodes.

This article deals with the actions needed to perform a snapshot on Google’s Compute Engine (GCE) infrastructure. A similar method can be used on AWS EC2 instances using EBS snapshots or any other form of snapshots such as LVM, ZFS or SAN. The steps described can be …

#DBHangOps 03/05/15 -- Group Replication, Multithreaded Replication, and more!

Hello everybody!

Join in #DBHangOps this Thursday, March, 05, 2015 at 11:00am pacific (19:00 GMT), to participate in the discussion about:

• Group Replication
• Multithreaded Replication
• Operational learnings with GTID
• New MySQL 5.7 defaults from Morgan Tocker

You can check out the event page at https://plus.google.com/events/cjbmf109r6d7isr715iupigsrq4 on Thursday to participate.

As always, you can still watch the #DBHangOps twitter search, the @DBHangOps twitter feed, or this blog post to get a link for the google hangout on …

DBAs often encounter situations where they need to kill queries to ensure there are no long-running queries on a MySQL server that would impact performance. Long-running queries can be the result of many factors. Fortunately, Percona Server contains some handy tools to remove problematic MySQL processes. I will highlight all of the tools via some examples in this post.

pt-kill:
There have been some good posts on this blog about the pt-kill tool, like this one by Arunjith Aravindan titled “How a set of queries can be killed in MySQL using Percona Toolkit’s pt-kill.” Let’s dive into pt-kill a bit further with a few more …

The General Availability of MySQL Cluster 7.4 has just been announced by Oracle.

The MySQL team at Oracle are excited to announce the General Availability of MySQL Cluster 7.4, ready for production workloads.

MySQL Cluster 7.4.4 can be downloaded from mysql.com and the release notes viewed in the MySQL docs.

Figure 1 provides a summary of the enhancements delivered in this release:

• Performance
  • 200M NoSQL Reads/Sec
  • 2.5M SQL Ops/Sec
  • 50% …

MySQL introduced the Event Scheduler in version 5.1.6. The Event Scheduler is a MySQL-level “cron job”, which will run events inside MySQL. Up until now, this was not a very popular feature, however, it has gotten more popular since the adoption of Amazon RDS – as well as similar MySQL database as a service offerings where there is no OS level.

What is important to understand about the Event Scheduler is that it does not have any protection against multiple execution (neither does linux cron). Let’s imagine you have created an event that executes every 10 seconds, but the logic inside the event (i.e. queries or stored procedure call) can …

default_tmp_storage_engine variable was introduced in 5.6.3, allowing the configuration of the default engine for temporary tables. This seems to be in the direction, as I commented before, of making MyISAM an optional engine. In 5.7, a separate tablespace is being created to hold those tables in order to reduce its performance penalty (those tables do not need to be redone if the server crashes, so extra writes are avoided).

However, I have seen many people assuming that because default_tmp_storage_engine has the value “InnoDB”, all temporary tables are created in InnoDB format in 5.6. This is not true: first, because implicit temporary tables are still being created in memory using …

Introduction

Causal consistency [1] is one of the consistency criteria that can be used on distributed databases as consistency criteria.

Distributed database provides causal consistency if read and write operations that are causally related are seen by every node of the distributed system in the same order. Concurrent writes may be seen in different order in diffrent nodes.  Causal consistency is waker than sequential consistency [2] but stronger than eventual consistency [3]. See earlier blog for more detailed description on eventual consistency https://blog.mariadb.org/eventually-consistent-databases-state-of-the-art/.

When a transaction performs a read operation followed later by a write operation, even on different object, the first read is said to be causally ordered before the write. This is because the …

MySQL 5.7 has had some great improvements within Performance Schema to be able to better trace what connections are doing, from adding memory information, through to transaction information, metadata locking, prepared statements, and even user variables, so far (there is still more to come in the next release – stay tuned).

Of course there are other improvements on top of this as well, such as the …

This Log Buffer Edition sheds light at some of the nifty blog post of the week from Oracle, SQL Server and MySQL.

Oracle:

Patch Set Update: Hyperion Data Relationship Management 11.1.2.3.504

The Hitchhiker’s Guide to the EXPLAIN PLAN Part 33: The mother of all SQL antipatterns?

MongoDB as a Glassfish Security Realm

E-Business Suite customers must ensure that their database remains on a level that is covered by Error Correction Support (ECS)

…

Up until a short while ago I was still using local.xml for modifications to a project-specific theme, even though 1.9 introduced the theme.xml file. The scenario I encountered which forced me to ditch local.xml is pretty interesting and made me understand the need for the theme.xml layout updates.

Basically, I was working on a website that now wanted to expand in a different country. The new store looked similar, but would have slightly different templates. Usually - in a similar situation - I would use a different theme under the same package (to make use of the “natural” theme fallback to “default”).

I couldn't use a different theme in this case because I was already using themes for certain pages that looked slightly different as a way to easily override template files without having to write any XML. (I was changing the theme in an observer event for specific pages.)

Then I tried using a new package. But that …