Description

  -----------

  In row binlog format, slave chose index when apply binlog use such order:

  1) primary key

  2) unique key without null columns

  3) normal index or unique key with null columns

  Actually, in situation 3 we should chose index with auto_increment column

  first, after this patch, the new order is

  1) primary key

  2) unique key without null columns

  3) normal index with auto_increment columns

  4) normal index without auto_increment columns or unique key with null columns