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Historically the MySQL query planner has been pretty bad, although it's improved significantly in the past couple years. It was particularly bad dealing with su
by michaelmior 13y ago
Historically the MySQL query planner has been pretty bad, although it's improved significantly in the past couple years. It was particularly bad dealing with subqueries as you mentioned, although several of the performance issues have been solved in MySQL 5.6.
https://mariadb.com/kb/en/subquery-optimizations-map/ https://mariadb.com/kb/en/subquery-optimizations-map/
- falcolas 13y agoYup, this. Of course, it hurts that there are probably less than 10 people in the world who fully understand the optimizer (and the majority are employed by Monty); though I'm sure the MySQL folks at Oracle are getting there.