High Performance MySQL

Appendix A. The SHOW STATUS and SHOW INNODB STATUS Commands

SHOW STATUS

The SHOW STATUS command allows you to view a snapshot of the many (over 120) internal status counters that MySQL maintains. These counters track particular events in MySQL. For example, every time you issue a SELECT query, MySQL increments the Com_select counter.

This command is valuable because early signs of performance problems often appear first in the SHOW STATUS output—but you have to be looking for them. By learning which counters are most important to server performance and how to interpret them, you’ll be well prepared to head off problems before they become an issue for your users.

This appendix is designed to do just that. Here you’ll find a brief summary of the more important counters MySQL provides, as well as some discussion of what to watch out for and how you might correct some of the problems highlighted here. We’ve attempted to group related items together rather than simply using an alphabetical list. And we’ve omitted the counters that have little relevance to MySQL performance. See the MySQL Reference Manual for a full list of the counters available in your version of MySQL.

Running the SHOW STATUS command repeatedly and examining the results is a very tedious process. To make life a bit easier, mytop automates much of the process. See Appendix B for more about mytop.

Warning

Note that these counters are stored as unsigned integers. On a 32-bit platform such as Intel x86, that means the counters ...