(Harrison Fisk) MySQL has two great features which historical haven’t played well together:

(Michael Paquier) IF EXISTS and IF NOT EXISTS are clauses allowing to return a notice message instead of an error if a DDL query running on a given object already exists or not depending on the DDL action done. If a given query tries to create an object when IF NOT EXISTS is specified, a notice mess

(Stewart Smith) The Example storage engine is meant to serve mainly as a code example of the stub of a storage engine for example purposes only (or so the code comment at the start of ha_example.cc reads). In reality however, it’s not very useful.

(Mark Callaghan) I ran single-threaded performance tests to compare MySQL using releases 4.0.30, 5.0.85, 5.1.63 and 5.6.11. On my simple tests 4.0.30 is almost 1.5X faster than 5.6.11. I think it is important to reduce these regressions.

(Todd Farmer) The MySQL general query log can be a useful debugging tool, showing commands received from clients. In versions through MySQL 5.5, you could count on the GQL to log every command it received – the logging happened before parsing.

(Joshua Prunier) I configure all our master databases to use row-based binary logging where I work. In my opinion it is a much safer option than row-base replication. The advantages and disadvantages of both types of MySQL replication are detailed in the online documentation here.

(Joshua Tolley) One of our clients, for various historical reasons, runs both MySQL and PostgreSQL to support their website. Information for user login lives in one database, but their customer activity lives in the other.

(Stewart Smith) This is one close to my heart. I’ve recently written on other storage engines: Where are they now: MySQL Storage Engines, The MERGE storage engine: not dead, just resting…. or forgotten and The MEMORY storage engine. Today, it’s the turn of MySQL Cluster.

(Andrew Dunstan) The old rule used to be that if you have a query that contained aggregated columns, you have to GROUP BY every other column selected. These days you are allowed to omit columns that are provably functionally dependent on one or more of the other grouped by columns.

(Mark Callaghan) For some workloads the InnoDB performance model is very simple. It must flush dirty pages as fast as storage will allow. With a few more bug fixes InnoDB in MySQL 5.6 should be able to do that. The performance model becomes a bit more complicated when you consider that there are two