Bug #68977 Documentation states that MRR cost optimizer is disabled by default
Submitted: 16 Apr 2013 21:50 Modified: 19 Apr 2013 17:00
Reporter: Justin Swanhart Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server: Documentation Severity:S5 (Performance)
Version:5.6.10 OS:Any
Assigned to: Paul DuBois CPU Architecture:Any

[16 Apr 2013 21:50] Justin Swanhart
Description:
The documentation here:
http://dev.mysql.com/doc/refman/5.6/en/mrr-optimization.html

The manual states:
By default, mrr is on and mrr_cost_based is off (use MRR whenever possible). See Section 8.8.5.2, “Controlling Switchable Optimizations”.

However, I have 5.6 set up with default settings and this appears not to be the case:
select @@optimizer_switch;

@@optimizer_switch:                                                                                                                                                                                                                                                                                                                               
...,mrr=on,mrr_cost_based=on,...

How to repeat:
Examine optimizer_switch

Suggested fix:
Change the default MRR behavior to disable cost based optimization or change the manual to reflect the true default.
[16 Apr 2013 21:50] Justin Swanhart
Add version info.
[17 Apr 2013 1:06] MySQL Verification Team
Thank you for the bug report.
[19 Apr 2013 17:00] Paul DuBois
Thank you for your bug report. This issue has been addressed in the documentation. The updated documentation will appear on our website shortly, and will be included in the next release of the relevant products.