As Rene wrote on the ProxySQL blog yesterday:

Although MySQL Query Cache was meant to improve performance, it has serious scalability issues and it can easily become a severe bottleneck.

This is indeed something we have observed in the MySQL team for a while.…

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This post was originally published on the MySQL Support Team Blog at https://blogs.oracle.com/mysqlsupport/entry/innodb_locks_analysis_why_is on 14 April 2017.

Consider the scenario that you execute a query. You expect it to be fast – typically subsecond – but now it take not return until after 50 seconds (innodb_lock_wait_timeout seconds) and then it returns with an error:

mysql> UPDATE world.City SET Population = Population + 999 WHERE ID = 130;
ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

You continue to investigate the issue using the sys.innodb_lock_waits view or the underlying Information Schema tables (INNODB_TRX, …

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This post was originally published on the MySQL Support Team Blog at https://blogs.oracle.com/mysqlsupport/entry/working_around_mysql_cluster_push on 5 August 2016.

I worked on an issue recently where a query was too slow when executed in MySQL Cluster. The issue was that Cluster has some restrictions when it comes to push down conditions.

As an example of this, consider the following query using the employees sample database. The query takes a look at the average salary based on how many years the employee has been with the company. As the latest hire date in the database is in January 2000, the query uses 1 February 2000 as the reference date.

Initially the query performs like (performance is with two data …

Some of the users may have noticed that .require files do not exist anymore in the MySQL test suite.

A .require is file is used along with 'require' mysqltest command. In test cases, the command 'require' is used to ensure MTR performs certain sanity checks.…

Keeping databases running consistently and continuously is crucial to many organizations. When your site or application fails to load because of problems with your databases, you risk losing revenues—especially a business with a high traffic site which is the main source of revenues. If it happens often enough, you’ll lose not only transactions but customers.

There are many reasons why a database system may be unavailable, or at least not consistently available. It could be straightforward problems with your databases, or it could be hardware limitations. There are several potentially weak components of a database system. It’s important to know where are the potential weak points and to have a clear sense of what’s required to maintain a highly available database system.

If this concept is moderately new to you, it may be overwhelming. However, please understand that it’s achievable and learnable. You can start by focusing …

Keeping databases running consistently and continuously is crucial to many organizations. When your site or application fails to load because of problems with your databases, you risk losing revenues—especially a business with a high traffic site which is the main source of revenues. If it happens often enough, you’ll lose not only transactions but customers.

There are many reasons why a database system may be unavailable, or at least not consistently available. It could be straightforward problems with your databases, or it could be hardware limitations. There are several potentially weak components of a database system. It’s important to know where are the potential weak points and to have a clear sense of what’s required to maintain a highly available database system.

If this concept is moderately new to you, it may be overwhelming. However, please understand that it’s achievable and learnable. You can start by focusing …

A few weeks ago I started experimenting with MySQL InnoDB cluster. As part of the testing, I tried to kill a node to see what happens to the cluster.

The good news is that the cluster is resilient. When the primary node goes missing, the cluster replaces it immediately, and operations continue. This is one of the features of an High Availability system, but this feature alone does not define the usefulness or the robustness of the system. In one of my previous jobs, I worked at testing a commercial HA system and I've learned a few things about what makes a reliable system.

Armed with this knowledge, I did some more experiments with InnoDB Cluster. The attempt from my previous article had no other expectation than seeing operations continue with ease (primary node …

Percona announces the GA release of Percona Server for MySQL 5.7.18-15 on May 26, 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 5.7.18, including all the bug fixes in it, Percona Server for MySQL 5.7.18-15 is the current GA release in the Percona Server for MySQL 5.7 series. Percona’s …

In this blog post, we’ll look at how ProxySQL and mirroring go together.

Overview

Let me be clear: I love ProxySQL, and I think it is a great component for expanding architecture flexibility and high availability. But not all that shines is gold! In this post, I want to correctly set some expectations, and avoid selling carbon for gold (carbon has it’s own uses, while gold has others).

First of all, we need to cover the basics of how ProxySQL manages traffic dispatch (I don’t want to call it mirroring, and I’ll explain further below).

ProxySQL receives a connection from the application, and through it we can have a simple SELECT or a more complex transaction. ProxySQL gets each query, passes them to the Query Processor, processes them, identifies if a query is mirrored, duplicates the whole MySQL session ProxySQL internal object and associates it to a mirror queue (which refer to a …

mysqldump is a very handy utility which can be useful if you work with MySQL databases ,you'll often need to backup your databases and restore them or import them back .

The mysqldump utility produces a set of SQL statements when executed against a database will create the same table structure and table rows or data.

mysqldump is fairly easy to use ,you can use it from the command line with different commands and options to tackle different use cases.

Lets see some practical examples to backup your databases with mysqldump :

Say you have a set of mySql databases ,you can backup them all with one command mysqldump --all-databases --user=root --password > backup-all-databases.sql

This will create backup-all-databases.sql file in your current directory which has a dump for all databases .

All the options are self explanatory --user and --password are for specifying mySql username and password …