Shinguz's blog

With 5.7.15 we had some strange installation errors which disappeared with 5.7.16. Further we found, that 5.7.15 still uses SysV init scripts and 5.7.16 has switched to SystemD…

Prepare the RPM repository server

Install the software to create a RPM repository server (on an Ubuntu web server):

If you have already Red Hat Enterprise Linux 7 (RHEL 7) or CentOS 7 in use you probably found out, that it is not that easy to install MySQL Enterprise Server because there are already pre-installed MariaDB 5.5 libraries:

The same should apply for the MySQL 5.7 Community Server…

Another idea we discussed (but does not fit to the problem) is lost space due to over-mounted directories. If you have some files in this directory they are not shown any more (= hidden) because they are over-mounted but they are still there an used space.

Today we had a very interesting phenomena at a customer. He complained that MySQL always get some errors of the following type:

FromDual has the pleasure to announce the release of the new version 0.10.6 of its popular Database Performance Monitor for MySQL, MariaDB, Galera Cluster and Percona Server fpmmm.

FromDual has the pleasure to announce the release of the new version 1.3.1 of its popular MySQL, Galera Cluster, MariaDB and Percona Server multi-instance environment MyEnv.

When analysing MySQL configuration and status information at customers it is always interesting to see how the applications behave. This can partially be seen by the output of the SHOW GLOBAL STATUS command. See also Reading MySQL fingerprints.

This week I was preparing the exercises for our MySQL/MariaDB for Beginners training. One of the exercises of the training is about MySQL spatial (GIS) features. I always tell customers: “With these features you can answer questions like: Give me all points of interest around me!”

A customer reported last month that MySQL does a full table scan (FTS) if a query was filtered by a INT value on a VARCHAR column. First I told him that this is not true any more because MySQL has fixed this behaviour long time ago. He showed me that I was wrong:

• max_user_connections Can be changed online in MySQL. Cannot be changed in MariaDB if value was set to 0.
• PERFORMANCE_SCHEMA is enabled in MySQL 5.6 and 5.7 by default. In MariaDB disabled by default.
• Replication incompatibilities from MariaDB (Master) to MySQL (Slave)
• MariaDB 10.2.0 still contains XtraDB 5.6. So MySQL 5.7 features cannot be used.
• MariaDB 10.2 Window Functions are missing in MySQL 5.7
• SHOW PROCESSLIST has additional column Progress in MariaDB.
• Progress indication in: mysqldump --progress-reports (default on) for MariaDB.
• MariaDB 10.0 on CentOS 7 uses still SysV init script. MySQL 5.6 on CentOS 7 uses SystemD init script.
• binlog_row_image is implemented in MySQL 5.6 and does not exist in MariaDB 10.0.
• MariaDB 10.1 and older (containing XtraDB 5.6) does not provide flexible/general tablespaces yet which where introduced by MySQL 5.7.
• EXPLAIN FOR CONNCECTION does exist in MySQL 5.7 and does not exist in MariaDB 10.1 or 10.2.

Other sources

• Sidegrade (MySQL - MariaDB - Percona Server)
• MariaDB versus MySQL - Features
• Differences Between the MySQL and MariaDB Query Optimizer
• MariaDB versus MySQL - Compatibility

MariaDB 10.2 has introduced some Window Functions for analytical queries.

To synchronize the data between the Galera Cluster and a new or re-entering Galera node Galera Cluster uses 2 different mechanisms:

Hi oli

Since MySQL 5.6.2 there is a new MySQL variable called binlog_rows_query_log_events. If you enable this variable MySQL will write the original SQL statements into the binary logs. More information about this variable you can find here:

How many connections can be opened concurrently against my MySQL or MariaDB database can be configured and checked with the following command:

InnoDB plugin is enabled.

The InnoDB Log File (innodb_log_file_size) size is possibly too small.
Choosing a too small InnoDB Log File size can have significant write performance impacts.

MySQL (InnoDB, PBXT, NDB, TokuDB) support Foreign Keys to show relatations between tables. Those relations can be enforced through Foreign Key Constraints.

InnoDB Force Recovery (innodb_force_recovery) is enabled. This mode should be used for data recovery purposes only. It prohibits writing to the data.