Super slow (day long) count(*) after upgrade to 5.6
It appears to be a change in the optimizer.  I haven't tracked down the exact setting that caused this yet but the explain on the 5.5 version was showing it using the Primary Key.  On 5.6 It was using the secondary char1(8) index.

Adding force index (primary) got it back to it's 3-5 minute count time.