<tr>
   <td>extra_row_info</td>
   <td>An object of class Extra_row_info</td>
   <td>The class Extra_row_info will be storing the information related
       to m_extra_row_ndb_info and partition info (partition_id and
       source_partition_id). At any given time a Rows_event can have both, one
       or none of ndb_info and partition_info present as part of Rows_event.
       In case both ndb_info and partition_info are present then below will
       be the order in which they will be stored.

       @verbatim
       +----------+--------------------------------------+
       |type_code |        extra_row_ndb_info            |
       +--- ------+--------------------------------------+
       | NDB      |Len of ndb_info |Format |ndb_data     |
       | 1 byte   |1 byte          |1 byte |len - 2 byte |
       +----------+----------------+-------+-------------+

       In case of INSERT/DELETE
       +-----------+----------------+
       | type_code | partition_info |
       +-----------+----------------+
       |   PART    |  partition_id  |
       | (1 byte)  |     2 byte     |
       +-----------+----------------+

       In case of UPDATE
       +-----------+------------------------------------+
       | type_code |        partition_info              |
       +-----------+--------------+---------------------+
       |   PART    | partition_id | source_partition_id |
       | (1 byte)  |    2 byte    |       2 byte        |
       +-----------+--------------+---------------------+

       source_partition_id is used only in the case of Update_event
       to log the partition_id of the source partition.

       @endverbatim
       This is the format for any information stored as extra_row_info.
       type_code is not a part of the class Extra_row_info as it is a constant
       values used at the time of serializing and decoding the event.
  </td>
 </tr>

uint net_field_length_size(const uchar *ptr) {
 if (*ptr <= 251) return 1;
 if (*ptr == 252) return 3;
 if (*ptr == 253) return 4;
 return 9;
}

uint64_t net_field_length_ll(uchar **packet) {
 const uchar *pos = *packet;
 if (*pos < 251) {
   (*packet)++;
   return (uint64_t)*pos;
 }
 if (*pos == 251) {
   (*packet)++;
   return (uint64_t)NULL_LENGTH;
 }
 if (*pos == 252) {
   (*packet) += 3;
   return (uint64_t)uint2korr(pos + 1);
 }
 if (*pos == 253) {
   (*packet) += 4;
   return (uint64_t)uint3korr(pos + 1);
 }
 (*packet) += 9; /* Must be 254 when here */
 return (uint64_t)uint8korr(pos + 1);
}

insert into t(a,b,c,d) values(1,2,3,4) 
insert into t(a,c,d) values(1,3,4) 

insert into t(a,b,c,d) values(1,2,3,4) null_map = 0xf 1111
insert into t(a,c,d) values(1,3,4) null_map = 0xb 1011

mysql> desc test;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| c1    | smallint    | YES  |     | NULL    |       |
| c2    | int         | YES  |     | NULL    |       |
| c3    | bigint      | YES  |     | NULL    |       |
| c4    | datetime    | YES  |     | NULL    |       |
| c5    | varchar(20) | YES  |     | NULL    |       |
| c6    | text        | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+

|    4 |    4 |    4 | 2024-01-16 15:16:39 | 44444 | 111111111122222233333444444 |

         04 00 04 00 00 00 04 00 00 00 00 00 00 00 99 B2 60 F4 27 05 34 34 34
34 34 1B 00 31 31 31 31 31 31 31 31 31 31 32 32 32 32 32 32 33 33 33 33 33 34
34 34 34 34 34