• Alexander Nozdrin's avatar
    Patch for Bug#12362125 (SP INOUT HANDLING IS BROKEN FOR TEXT TYPE). · 8f795799
    Alexander Nozdrin authored
    Attempts to assign value to a table column from trigger by using
    NEW.column_name pseudo-variable might result in garbled data.
    That happened when:
      - the column had a BLOB-based type (e.g. TEXT)
        and
      - the value being assigned was retrieved from stored routine variable
        of the same type.
    
    The problem was that BLOB values were not copied correctly in this
    case. Instead of doing a copy of a real value, the value's representation
    in record buffer was copied. This representation is essentially a
    pointer to a buffer associated with the virtual table for routine
    variables where the real value is stored. Since this buffer got
    freed once trigger was left or could have changed its contents when
    new value was assigned to corresponding routine variable such a shallow
    copying resulted in garbled data in NEW.colum_name column.
    
    It worked in 5.1 due to a subtle bug in create_virtual_tmp_table():
      - in 5.1 create_virtual_tmp_table() returned a table which
        had db_low_byte_first == false.
      - in 5.5 and up create_virtual_tmp_table() returns a table which
        has db_low_byte_first == true.
    Actually, db_low_byte_first == false only for ISAM storage engine,
    which was deprecated and removed in 5.0.
    
    Having db_low_byte_first == false led to getting false in the
    complex condition for the 2nd "if" in field_conv(), which in turn
    led to copy-blob-behavior as a fall-back strategy:
      - to->table->s->db_low_byte_first was true (correct value)
      - from->table->s->db_low_byte_first was false (incorrect value)
    
    In 5.5 and up that condition is true, which means blob-values are
    not copied.
    8f795799
trigger.result 67.5 KB