In BUG#49562 we fixed the case where numeric user var events
would not serialize the flag stating whether the value was signed
or unsigned (unsigned_flag). This fixed the case that the slave
would get an overflow while treating the unsigned values as
signed.
In this bug, we find that the unsigned_flag can sometimes change
between the moment that the user value is recorded for binlogging
purposes and the actual binlogging time. Since we take the
unsigned_flag from the runtime variable data, at binlogging time,
and the variable value is comes from the copy taken earlier in
the execution, there may be inconsistency in the
User_var_log_event between the variable value and its
unsigned_flag.
We fix this by also copying the unsigned_flag of the
user_var_entry when its value is copied, for binlogging
purposes. Later, at binlogging time, we use the copied
unsigned_flag and not the one in the runtime user_var_entry
instance.
variable
The User_var_log_event was not serializing the unsigned
flag. This would cause the slave to always assume signed values.
We fix this by extending the User_var_log_event to also contain
information on the unsigned_flag, meaning that it gets into the
binlog as well, therefore the slave will get this information as
well. Events without information on unsigned flag (old events)
are treated as they were before (always signed: unsigned_flag=
FALSE).
The information on the unsigned_flag, is shipped in an extra byte
appended to the end of the User_var_log_event and added by this
patch. This extra byte holds values for general purpose
User_var_log_event flags which are now packed in the binlog as
well. One of these flags contains information about whether the
value is signed or unsigned (currently this extra byte is only
used to hold data on the unsigned flag, in the future we can use
it to pack extra flags if there is the need to).
