timestamp primary key 
 
Since TIMESTAMP values are adjusted by the current time zone  
settings in both numeric and string contexts, using any 
expressions involving TIMESTAMP values as a  
(sub)partitioning function leads to undeterministic behavior of  
partitioned tables. The effect may vary depending on a storage  
engine, it can be either incorrect data being retrieved or  
stored, or an assertion failure. The root cause of this is the  
fact that the calculated partition ID may differ from a  
previously calculated ID for the same data due to timezone  
adjustments of the partitioning expression value. 
 
Fixed by disabling any expressions involving TIMESTAMP values  
to be used in partitioning functions with the follwing two 
exceptions: 
 
1. Creating or altering into a partitioned table that violates 
the above rule is not allowed, but opening existing such tables 
results in a warning rather than an error so that such tables 
could be fixed. 
 
2. UNIX_TIMESTAMP() is the only way to get a 
timezone-independent value from a TIMESTAMP column, because it 
returns the internal representation (a time_t value) of a 
TIMESTAMP argument verbatim. So UNIX_TIMESTAMP(timestamp_column)
is allowed and should be used to fix existing tables if one 
wants to use TIMESTAMP columns with partitioning.