Hi..just working on integrating some stuff and trying to understand something in regard to one of the mysql table under each mailboxgroup

Table Name: open_conversation
Table Data:
mailbox_id hash conv_id
428 baEGgm5CGreA8occjEsVzi4MmHo= 260
428 QijJkMW,yPWQ1AUoA+eHTNuD9Gk= 261
428 5bIhzyS,AX7Z2CeqM+HRZYLxke0= 262
428 dIlnflkUn0lAoPJHPpSnEPjcrVk= 264

Mailbox_id = Same as ID field as in zimbra.mailbox table
Hash = ?
Conv_id = ?

How does zimbra link/create these HASH and CONV_ID to messages?