In order to handle CHAR() fields, 8 bits were reserved for
the size of the CHAR field. However, instead of denoting the
number of characters in the field, field_length was used which
denotes the number of bytes in the field.
Since UTF-8 fields can have three bytes per character (and
has been extended to have four bytes per character in 6.0),
an extra two bits have been encoded in the field metadata
work for fields of type Field_string (i.e., CHAR fields).
Since the metadata word is filled, the extra bits have been
encoded in the upper 4 bits of the real type (the most
significant byte of the metadata word) by computing the
bitwise xor of the extra two bits. Since the upper 4 bits
of the real type always is 1111 for Field_string, this
means that for fields of length <256, the encoding is
identical to the encoding used in pre-5.1.26 servers, but
for lengths of 256 or more, an unrecognized type is formed,
causing an old slave (that does not handle lengths of 256
or more) to stop.
without PK
Bug#31609 Not all RBR slave errors reported as errors
bug#32468 delete rows event on a table with foreign key constraint fails
The first two bugs comprise idempotency issues.
First, there was no error code reported under conditions of the bug
description although the slave sql thread halted.
Second, executions were different with and without presence of prim key in
the table.
Third, there was no way to instruct the slave whether to ignore an error
and skip to the following event or to halt.
Fourth, there are handler errors which might happen due to idempotent
applying of binlog but those were not listed among the "idempotent" error
list.
All the named issues are addressed.
Wrt to the 3rd, there is the new global system variable, changeble at run
time, which controls the slave sql thread behaviour.
The new variable allows further extensions to mimic the sql_mode
session/global variable.
To address the 4th, the new bug#32468 had to be fixed as it was staying
in the way.
