query_cache_size=0 is not enough

Last week at the OUG Harmony conference thanks to Dimitri Kravtchuk I learned that setting query_cache_size=0 does not disable and remove locking from the Query Cache. You actually need to also set query_cache_type=0. This appears to been a bug, seen in the presently still open MySQL bugs database entry #38511 .

My recommendation to customers now is to set both variables on all existing MySQL versions if you are not using the MySQL Query Cache.

Thanks to the Performance Schema in MySQL 5.5 for uncovering this. More information in Dimitri’s detailed post at MySQL Performance: Using Performance Schema

Details of all MySQL presentations at OUG Harmony 2011 in Helsinki, Finland.

Tagged with: Databases MySQL

Why using production workloads over simulated workloads is critical

Why using production workloads over simulated workloads is critical

AI-Assisted SQL Tuning Last week in his keynote speech at Percona Live Bay Area 2026 , Andy Pavlo presented Databases: The Final Boss of Agents and provided some useful insights into query optimization of simulated workloads leveraging AI.

Improving your MySQL Security Posture Presentation

Improving your MySQL Security Posture Presentation

At the MySQL BR Conference 2025 I had the opportunity to speak about Improving Your MySQL Security Posture. You can find a copy of my slides on my Presentations , and a Portugese (Brazil) translation.

MySQL and Heatwave Summit Presentation

MySQL and Heatwave Summit Presentation

Last week I had the opportunity to speak at the MySQL and Heatwave Summit in San Francisco. I discussed the impact of the new MySQL 8.0 default caching_sha2_password authentication, replacing the mysql_native_password authentication that was the default for approximately 20 of the 30 years that MySQL has existed.