Problem:
=======
InnoDB wrongly stores the primary key field in externally
stored off page during bulk insert operation. This leads
to assert failure.
Solution:
========
row_merge_buf_blob(): Should store the primary key fields
inline. Store the variable length field data externally
based on the row format of the table.
row_merge_buf_write(): check whether the record size exceeds
the maximum record size.
row_merge_copy_blob_from_file(): Construct the tuple based on
the variable length field
