When a write query is sent to Percona XtraDB Cluster all the nodes store the writeset on a file called gcache. By default the name of that file is galera.cache and it is stored in the MySQL datadir. This is a very important file, and as usual with the most important variables in MySQL, the […]
Galera replication for MySQL brings not only the new, great features to our ecosystem, but also introduces completely new maintenance techniques. Are you concerned about adding such new complexity to your MySQL environment? Perhaps that concern is unnecessarily. I am going to present here some simple tips that hopefully will let fresh Galera users prevent […]
The need to have multiple instances of MySQL (the well-known mysqld process) running in the same server concurrently in a transparent way, instead of having them executed in separate containers/virtual machines, is not very common. Yet from time to time the Percona Support team receives a request from a customer to assist in the configuration of […]
In my last post, “A closer look at the MySQL ibdata1 disk space issue and big tables,” I looked at the growing ibdata1 problem under the perspective of having big tables residing inside the so-called shared tablespace. In the particular case that motivated that post, we had a customer running out of disk space in his […]
Reconfiguring replication has always been a challenge with MySQL. Each time the replication topology has to be changed, the process is tedious and error-prone because finding the correct binlog position is not straightforward at all. Global Transaction IDs (GTIDs) introduced in MySQL 5.6 aim at solving this annoying issue. The idea is quite simple: each […]
On July 16 I’ll be presenting my next webinar focusing on common mistakes committed by MySQL users. How to Avoid Even More of the Common (but Deadly) MySQL Development Mistakes “Why can’t I just save my data to a file?” Using an SQL database seems so complex to get right, and for good reason. The […]
In my previous post I showed you how to setup Percona XtraDB Cluster 5.6 on Docker. This time I will show you how to setup Percona ClusterControl and add the existing Percona XtraDB Cluster 5.6 that we’ve managed to setup from the previous post. Let us note the following details about our existing containers: 172.17.0.2 […]
We recently released a new version of Percona Cloud Tools with MySQL monitoring capabilities. Join me June 25 and learn the details about all of the great new features inside Percona Cloud Tools – which is now free in beta. The webinar is titled “Monitoring All (Yes, All!) MySQL Metrics with Percona Cloud Tools” and begins at […]
MySQL has status variables “questions” and “queries” which are rather close but also a bit different, making it confusing for many people. The manual describing it might not be very easy to understand:
The number of statements executed by the server. This variable includes statements executed within stored programs, unlike the Questions variable. It does not count COM_PING or COM_STATISTICS commands.
The number of statements executed by the server. This includes only statements sent to the server by clients and not statements executed within stored programs, unlike the Queries variable. This variable does not count COM_PING, COM_STATISTICS, COM_STMT_PREPARE, COM_STMT_CLOSE, or COM_STMT_RESET commands.
In a nutshell if you’re not using prepared statements the big difference between those is what “Questions” would count stored procedure calls as […]