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MySQL 8.0 Reference Manual  /  Optimization  /  Controlling the Query Optimizer

Pre-General Availability Draft: 2017-10-20

8.9 Controlling the Query Optimizer

MySQL provides optimizer control through system variables that affect how query plans are evaluated, switchable optimizations, optimizer and index hints, and the optimizer cost model.

The server also maintains statistics about column values, although the optimizer does not yet use this information.


User Comments
  Posted by Richard Prout on July 30, 2008
I had a view with probably 20 joins in. tables typically only had 100 rows. query would initially take 20-30seconds. i set the optimiser search depth down to 3 and got that time down to 90ms.
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