Some applications have a heavy write workload on a few records – for instance when incrementing a global counter: this is called a write hotspot. Because you cannot update the same row simultaneously from multiple threads, this can lead to performance degradation. When using Percona XtraDB Cluster (PXC), some users try to solve this specific issue by writing on multiple nodes at the same time. Good idea or bad idea? Read on!

Simultaneous writes on a standalone InnoDB server

Say you have these 3 transactions being run simultaneously (id is the primary key of the table):

# T1
UPDATE t SET ... WHERE id = 100
# T2
UPDATE t SET ... WHERE id = 100
# T3
UPDATE t SET ... WHERE id = 101

All transactions will require a row lock on the record they want to modify. So T3 can commit at the same time than T1 and/or T2, because it will …

Tue, 2015-06-02 19:07geoff_montee_g

Most MariaDB users are probably aware of the privilege system available in MariaDB and MySQL. Privileges control what databases, tables, columns, procedures, and functions a particular user account can access. For example, if an application stored credit card data in the database, this data should probably be protected from most users. To make that happen, the DBA might disallow access to the table or column storing this sensitive data.

However, sometimes the privilege system isn't sufficient to secure data. Sometimes data needs to be secured beyond tables and columns. In those cases, row-level security (sometimes abbreviated RLS) may be necessary. Possible use cases for row-level security are:

• A government agency might only allow a user to see a row based on classification (CONFIDENTIAL, …

In my previous post, I showed you a way to store tweets in MySQL, and then use Perl to automatically publish them on Twitter.

In this post, we will look at automatically sending a “thank you” to people who retweet your tweets — and we will be using Perl and MySQL again.

Just like in the first post, you will need to register your application with Twitter via apps.twitter.com, and obtain the following:

consumer_key
consumer_secret
access_token
access_token_secret

One caveat: Twitter has a rate limit on how often you may connect with your application — depending upon what you are trying to do. See the Rate Limiting and …

MySQL 5.5.44 was recently released (it is the latest MySQL 5.5, is GA), and is available for download here:

http://dev.mysql.com/downloads/mysql/5.5.html

This release, similar to the last 5.5 release, is mostly uneventful.

There were 0 “Functionality Added or Changed” items this time, and just 15 overall bugs fixed.

Out of the 15 bugs, there were 5 InnoDB bugs (1 of which also spans partitioning), 1 security-related bug, 1 performance-related, and 3 additional potential crashing bugs. Here are the ones worth noting:

• InnoDB: An assertion was raised on shutdown due to XA PREPARE transactions holding explicit locks.
• InnoDB: Removal of a foreign key object from the data dictionary cache during error handling caused the server to exit.
• InnoDB: SHOW ENGINE …

Providing a suitable High Availability (HA) solution for each database system is one of the challenging tasks for a DBA and here we have to answer some questions like the following ones:

1. What is the cost for that HA solution?
2. Is it required to change the system structure or the DB design to use that HA solution?
3. Is it complicate to understand, use or maintain ?

Choosing the suitable HA solution for each system will depend on the answers of such questions …
In this post, I’m going to write about MySQL Master High Availability MHA as a nice tool which provides HA for MySQL by performing automatic fail-over or fast online master switching with almost no downtime!

Before going through more details about MHA, let’s first answer the previous questions:

1. MHA is a free opensource tool, no cost to …

Performance Schema (PS) has been the subject of many, many recent discussions, presentations, and articles.  After its release in MySQL 5.7, PS has become the main actor for people who want to take the further steps in MySQL monitoring. At the same time, it has become clear that Oracle intends to make PS powerful with so many features and new instrumentation that old-style monitoring will begin to look like obsolete tools from the Stone Age.

This article will explain PS and provide guidance on what needs to be done in order to use it effectively.

What I am not going to do is to dig into specific performance issues or address polemics about what PS is and what, in a Utopian vision, it should be. I have seen too many presentations, articles and comments like this and they are not productive, nor are they in line with my target which is: keep people informed on how to do things EASILY.

For the scope of this …

Performance Schema (PS) has been the subject of many, many recent discussions, presentations, and articles.  After its release in MySQL 5.7, PS has become the main actor for people who want to take the further steps in MySQL monitoring. At the same time, it has become clear that Oracle intends to make PS powerful with so many features and new instrumentation that old-style monitoring will begin to look like obsolete tools from the Stone Age.

This article will explain PS and provide guidance on what needs to be done in order to use it effectively.

What I am not going to do is to dig into specific performance issues or address polemics about what PS is and what, in a Utopian vision, it should be. I have seen too many presentations, articles and comments like this and they are not productive, nor are they in line with my target which is: keep people informed on how to do things EASILY.

For the scope of this …

Using twitter can sometimes feel like driving downtown, screaming what you want to say out the window, and hoping someone hears you. There might be tens of thousands of people downtown, but your message will only be heard by a few. Because of this, your best bet is to repeat your message as often as possible.

Twitter is free and if you want to reach as many people as possible, it’s another great tool for getting your message out there. But sending tweets on a scheduled basis can be a pain. There are client programs available which allow you to schedule your tweets (Hootsuite is one I have used in the past). You can load your tweets in the morning, and have the application tweet for you all day long. But you still have to load the application with your tweets—one by one.

A friend of mine asked me if there was a way to send the same 200 tweets over and over again, spaced out …

One of my favorite tools for query optimization is profiling. But recently I noticed this warning:

mysql> set profiling=1;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+----------------------------------------------------------------------+
| Level   | Code | Message                                                              |
+---------+------+----------------------------------------------------------------------+
| Warning | 1287 | '@@profiling' is deprecated and will be removed in a future release. |
+---------+------+----------------------------------------------------------------------+

After looking through certain documentation , I should indeed start using the Performance Schema to get this information.

Okay, so let’s give that a try.

I confirmed that I started MySQL 5.6.23 …

We previously covered basic tuning and configuration best practices for MyQL Galera Cluster on AWS. In this blog post, we’ll go over some AWS features/tools that you may find useful when managing Galera on Amazon Cloud. This won’t be a detailed how-to guide as each tool described below would warrant its own blog post. But this should be a good overview of how you can use the AWS tools at your disposal.

EBS backups

If you have chosen EBS volumes as storage for your database (you could have chosen ephemeral volumes too), you can benefit greatly from their ability of taking snapshots of the data.

In general, there are two ways of running backups:

• Logical backup executed in the form of mysqldump, mydumper or similar tools. The result of it is a set of SQL commands …