In this blog, we’ll look at how queries in systems with parallel processing can return rows in a non-deterministic order (and how to fix it).

Short story:

Do not rely on the order of your rows if your query does not use

ORDER BY

. Even with

ORDER BY

, rows with the same values can be sorted differently. To fix this issue, always add

ORDER BY ... ID

 when you have

LIMIT N

.

Long story:

While playing with MariaDB ColumnStore and Yandex ClickHouse, I came across a very simple case. In MariaDB ColumnStore and …

Amazon Relational Database Service (RDS) is a hosted database service in the AWS cloud. If your organization’s data is stored in one of the popular database systems, but on a company server or perhaps you’re renting a dedicated server, you might want to consider switching to Amazon RDS.  With Amazon RDS, you can choose from several relational database systems:  MySQL, MariaDB, Oracle, Postgres, and SQL Server, as well as Amazon Aurora.

There are many advantages to Amazon RDS, such as server scaling and load balancing of user traffic. Best of all, it can reduce the operational costs of running database software like MySQL. With Amazon RDS, you don’t need to worry about performing security updates, patching the operating system, or tuning the database. In fact, some of the patches Amazon deploys for MySQL and MariaDB are specifically designed to get better performance in a cloud setting.  Let’s look at some major …

Welcome to another post in the series of Percona Live featured session blogs! In these blogs, we’ll highlight some of the session speakers that will be at this year’s Percona Live conference. We’ll also discuss how these sessions can help you improve your database environment. Make sure to read to the end to get a special Percona Live 2017 registration bonus!

In this Percona Live featured session, we’ll meet Ilya Kosmodemiansky, CEO and Consultant of Data Egret. His session is Linux IO Internals for Database Administrators. Input/output performance problems are an …

In this blog, we’ll look at how to resolve MySQL error code 1215: “Cannot add foreign key constraint”.

Our Support customers often come to us with things like “My database deployment fails with error 1215”, “Am trying to create a foreign key and can’t get it working” or “Why am I unable to create a constraint?” To be honest, the error message doesn’t help much. You just get the following line:

ERROR 1215 (HY000): Cannot add foreign key constraint

But MySQL never tells you exactly WHY it failed. There’s actually a multitude of reasons this can happen. This blog post is a compendium of the most common reasons why you can get ERROR 1215, how to diagnose your case to find which one is affecting you and potential solutions for adding the foreign key.

Overview

In this post I will explain how to transfer a partitioned table using transportable tablespaces on MySQL 5.6. Note that the operation is not officially supported until MySQL 5.7, as the discard tablespace operation will fail if it is run against a partitioned table on MySQL 5.6.

The workaround is transferring each individual partition as if it was a standalone table. Continue reading to learn more about the detailed procedure.

Steps

1. Create the same table structure on the destination server:

[root@mysqlsandbox ~]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.35-80.0 Percona Server (GPL), Release 80.0, Revision f113994f31

Copyright (c) 2009-2016 Percona LLC and/or its affiliates
Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. …

The MariaDB project is pleased to announce the immediate availability of MariaDB 10.2.5 Release Candidate (RC). See the release notes and changelog for details. Download MariaDB 10.2.5 Release Notes Changelog What is MariaDB 10.2? MariaDB APT and YUM Repository Configuration Generator Thanks, and enjoy MariaDB!

The post MariaDB 10.2.5 RC now available appeared first on MariaDB.org.

In this blog post, we’ll look at some of the available PMP profiling tools.

While debugging or analyzing issues with Percona Server for MySQL, we often need a quick understanding of what’s happening on the server. Percona experts frequently use the pt-pmp tool from Percona Toolkit (inspired by http://poormansprofiler.org).

The

pt-pmp

 tool collects application stack traces GDB and then post-processes them. From this you get a condensed, ordered list of the stack traces. The list helps you understand where the application spent most of the time: either running something or waiting for something.

Getting a profile with

via GIPHY I was just reading over StackOverflow’s 2017 Developer survey. As it turns out there were some surprising findings. Join 33,000 others and follow Sean Hull on twitter @hullsean. One that stood out was databases. In the media, one hears more and more about NoSQL databases like Cassandra, Dynamo & Firebase. Despite all that … Continue reading What engineering roles are most in demand at startups? →

Percona announces the GA release of Percona Server for MySQL 5.7.17-13 on April 5, 2017. Download the latest version from the Percona web site or the Percona Software Repositories. You can also run Docker containers from the images in the Docker Hub repository.

Based on MySQL 5.7.17, including all the bug fixes in it, Percona Server for MySQL 5.7.17-13 is the current GA release in the Percona Server for MySQL 5.7 series. Percona’s …

We previously compared two high availability solutions for MySQL - MHA and MariaDB Replication Manager and looked into how they performed fail-over. In this blog post, we’ll see how ClusterControl stacks up against these solutions. Since MariaDB Replication Manager is under active development, we decided to take a look at the not yet released version 1.1.

Flapping Related resources  MySQL Replication failover: MaxScale vs MHA (part 1)  MySQL Replication failover: MaxScale vs MHA (part 2)  MySQL …