Row-based replication requires the types of columns on the
master and slave to be approximately the same (some safe
conversions between strings are allowed), but does not
allow safe conversions between fields of similar types such
as TINYINT and INT.
This patch implement type conversions between similar fields
on the master and slave.
The conversions are controlled using a new variable
SLAVE_TYPE_CONVERSIONS of type SET('ALL_LOSSY','ALL_NON_LOSSY').
Non-lossy conversions are any conversions that do not run the
risk of losing any information, while lossy conversions can
potentially truncate the value. The column definitions are
checked to decide if the conversion is acceptable.
If neither conversion is enabled, it is required that the
definitions of the columns are identical on master and slave.
Conversion is done by creating an internal conversion table,
unpacking the master data into it, and then copy the data to
the real table on the slave.
This patch adds the ability to store extra field metadata in the table
map event. This data can include pack_length() or field_lenght() for
fields such as CHAR or VARCHAR enabling developers to add code that
can check for compatibilty between master and slave columns. More
importantly, the extra field metadata can be used to store data from the
master correctly should a VARCHAR field on the master be <= 255 bytes
while the same field on the slave is > 255 bytes.
The patch also includes the needed changes to unpack to ensure that data
which is smaller on the master can be unpacked correctly on the slave.
WL#3915 : (NDB) master's cols > slave
Slave starts accepting and handling rows of master's tables which have more columns.
The most important part of implementation is how to caclulate the amount of bytes to
skip for unknown by slave column.
