You're correct, I was looking at that and thinking 'gee, why do these link back to one another? without foreign key support, that's a nightmare!' But I don't think there needs to be much more than a few tweaks to the existing tables to get this working.
Aaron On Mon, 31 Mar 2003, Magnus Sundberg wrote: > Hi Aaron, > I did not understand your reply, if you look at what is linked with > what. I see the following > MESSAGEBLK record message_idnr points to a record in the messages table. > MESSAGE record message_idnr is UNIQUE. > You need to add at least one pointer to the messages table, called > something linke MESSAGEBLOCK or whatever. > But I beleive one mail message consists of several messageblocks, An > undefinite number. > > Please correct my reasoning. > > Magnus > > Aaron Stone wrote: > > Actually, I believe that this layer would work fine as it is already. The > > 'message' table links a messageblk to a mailbox. It could easily be that a > > single messageblk is referenced by several rows in the message table and > > therefore appears in several people's mailboxes. > > > > Aaron > > > > > > On Mon, 31 Mar 2003, Magnus Sundberg wrote: > > > > > >>Hello Jeff, > >> From your database design it looks like that you change the > >>mailbox_idnr record in the messages table when you move mail from one > >>mailbox folder to another. I hope this is possible at least by the IMAP > >>protocoll? > >> > >>The problem as I see it is the relational database structure itself. You > >>have this pointing relation MESSAGEBLK->MESSAGE->MAILBOX->USERS, quite > >>the opposite to when you are programming linked trees on a computer. > >> > >>I beleive you could achevie this by another database layer, one for each > >>user and messageblk. Let's divide the messageblk into two parts > >>msgblkptr (MessageBlockPointer) and msgblkdata (MessageBlockData). > >>The pointer is unique for every user and points to the Data. > >>So if you send 1000 people a message you will get 1000 pointers, but > >>just one datablock. > >>When you delete a pointer, you check if there are any more pointers to > >>the block, if the ointercount is zero, you also delete the data block. > >> > >>What is wrong with my reasoning? > >> > >>Except for that this will be difficult to merge into the installed base. > >> > >>What will the performance hit be? > >> > >>Is it worth the effort of changing? > >> > >>Please explain the problem of crosslinking. > >> > >>Is this one of exchanges weak points? > >> > >>/Magnus > >> > >>Jeff Brenton wrote: > >> > >>>Hello Magnus, > >>> > >>>MS> Is there one new MESSAGEBLK created in the database for each user for > >>>MS> these messages, or is the MESSAGEBLK shared between the users. > >>> > >>>Yes, there is a complete message (1 entry into message and 2 or more > >>>into messageblk tables) for each recipient. Send a message to 1,000 > >>>people on the system, and 1,000 copies of it exist. > >>> > >>>The only system that does NOT do that, to my knowledge, is Exchange > >>>Server; it maintains a separate table internally to keep track of > >>>which users have seen/deleted the message, and doesn't actually delete > >>>it until ALL have seen it. > >>> > >>>While this is more space efficient, it is also a nightmare if certain > >>>users decide to move the message to one of their mailbox folders > >>>(maintained on the server, rather than on their local machine), > >>>because the copy makes a new link... message bodies can be cross > >>>linked endlessly, making problems if you ever need to restore the > >>>database. > >>> > >>>At least some backup procedures "fix" this by saving individual > >>>"snapshots" of the tables, so you end up with a backup containing a > >>>complete copy of these group messages for each user who hasn't purged > >>>it from their mailbox, and the restore ends up having multiple copies > >>>anyway... > >>> > >> > >> > >> > >> > >>_______________________________________________ > >>Dbmail mailing list > >>Dbmail@dbmail.org > >>https://mailman.fastxs.nl/mailman/listinfo/dbmail > >> > > > > > > _______________________________________________ > > Dbmail mailing list > > Dbmail@dbmail.org > > https://mailman.fastxs.nl/mailman/listinfo/dbmail > > > > > > > _______________________________________________ > Dbmail mailing list > Dbmail@dbmail.org > https://mailman.fastxs.nl/mailman/listinfo/dbmail >
