Using the libmysql client you can unpack a dynamic column using mariadb_dyncol_unpack(), but the data returned in the column_keys and values needs to be freed after use. It is not documented how to do this (i.e. which free function to call) but neither free(), HeapFree() or mariadb_dyncol_free() works. Looking at the code, sf_malloc is used to allocate the data but I can's see a corresponding function that will free data using sf_free().