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Prevent MySQL downtime: Set max_user_connections

One of the common causes of downtime with MySQL is running out of connections. Have you ever seen this error? “ERROR 1040 (00000): Too many connections.” If you’re working with MySQL long enough you surely …


How to debug long-running transactions in MySQL

Among the many things that can cause a “server stall” is a long-running transaction. If a transaction remains open for a very long time without committing, and has modified data, then other transactions could block …


Ultimate MySQL variable and status reference list

I am constantly referring to the amazing MySQL manual, especially the option and variable reference table. But just as frequently, I want to look up blog posts on variables, or look for content in the …


Tradeoffs: Updates versus Range Queries

Sorry for the delay, now on to range queries and lenient updates. Let’s call them queries and updates, for short. So far, I’ve shown that B-trees (and any of a number of other data structures) …


Living with backups

Everyone does backups. Usually it’s some nightly batch job that just dumps all MySQL tables into a text file or ordinarily copies the binary files from the data directory to a safe location. Obviously both …