Tweet

MySQL stores several files on disk. Even in MySQL 8 where the data dictionary is stored in InnoDB tables, there are still all the tablespace files. Different file system behave differently, and one particular challenge is case sensitivity. On Microsoft Windows, the case does not matter, on Linux the case is important, and on macOS the case of the file names is preserved but the operating system by default makes it look like it is case insensitive.

Which convention that is the correct depends on your personal preference and use case. Between case sensitivity and case insensitivity, it basically boils down to whether mydb, MyDB, and MYDB should be the same identifier or three different ones. Since …

Tweet

When things go horrible wrong and a process crashes, one of the most powerful things to investigate the cause of the crash is a core dump. As the amount of memory allocated to processes such as MySQL has increased – in some cases approaching 1TiB of memory – enabling core dumps can cause problems of their own. MySQL Server 8.0.14 and later supports an option to reduce the size of the core dump which will be discussed in this blog.

Typically the largest single user of memory for MySQL is the InnoDB buffer pool. This is used to cache the data and indexes for tables using the InnoDB storage engine (the default). It is rarely important to know what is stored in the InnoDB buffer pool when investigating a crash, so a good way to …

Tweet

MySQL 8.0 introduced a new feature that allows you to persist configuration changes from inside MySQL. Previously you could execute SET GLOBAL to change the configuration at runtime, but you needed to update your MySQL configuration file in order to persist the change. In MySQL 8.0 you can skip the second step. This blog discuss how this works and how to backup and restore the configuration.

Using SET PERSIST to set a variable and the persisted_variables table in the Performance Schema to get a list of persisted variables.Persisting Variables

You persist changes with either the SET PERSIST or SET PERSIST_ONLY …

With MySQL 5.6 just gone GA, I thought it would be good to take a look at the changes in options and variables that comes with the new release.

First of all, several of the existing options have get new default values. As James Day already have written a good post about that in his blog, I will refer to that instead of going through the changes. For a general overview of the new features and improvements, the recent blogs by Rob Young and Peter Saitsev are good starting points together with the …

I was listening today to the OurSQL Episode 36: It's Not Our (De)fault! Part 1. As usual, Sheeri and Sarah are very informational and entertaining while explaining the innards of MySQL and their best practices.
Being a DBA oriented show, there was an omission in this podcast. There was no mention of custom groups that you can have for your my.cnf. This is mostly useful for developers. If your application requires some specific settings, instead of using a separated configuration file, you can use a different group, and then instruct your client applications to use that group.
By default, all client applications read the "[client]" group.
But you can tell your client to read a group that you can call whatever you like.
For example, with this configuration file,

[client] …

Here’s a sneak peek at a video matrix — this is all the videos that include Pythian Group employees at the MySQL conference. I hope to have all the rest of the videos processed and uploaded within 24 hours, with a matrix similar to the one below (but of course with many more sessions).

The Maatkit toolkit is a real blessing for the MySQL DBA. And while its documentation is pretty good, in some cases it’s necessary to read carefully a second and third time to make sure you are not missing an important piece of information. In this article I will comment on mk-table-chksum and mk-table-sync. My comments are mostly aimed at those DBAs who are considering using these utilities with medium or larger-sized databases.

–replicate

This option allows you to store the checksum results on the master, in a table that will get replicated to the slaves. Although it might seem like overhead for a simple check, it really simplifies your life, especially when used in combination with …