Extension:Chat/chathistory table

mysql> describe chathistory; +---+-+--+-+-+---+ +---+-+--+-+-+---+ +---+-+--+-+-+---+
 * Field    | Type        | Null | Key | Default | Extra |
 * server   | varchar(32) | NO   | PRI |         |       |
 * group    | varchar(64) | NO   | PRI |         |       |
 * subgroup | varchar(64) | NO   | PRI |         |       |
 * leaf     | varchar(64) | NO   | PRI |         |       |
 * leafvalue | text       | NO   |     | NULL    |       |
 * timestamp | int(11)    | NO   |     | 0       |       |