Ilja Booij wrote:
Hi all,
The 2.0 branch of dbmail is becoming "stable". A lot of code has been
changed, almost all of it in the database layer.
* merging db code
As I mentioned about1 1/2, 2 months ago, the database code has been
merged together, leaving only 2 (MySQL and PostgreSQL) database specific
.c files of about 300 lines of C-code each. Implementing code for
additional database
systems (Oracle, DB2, Firebird, SAPdb etc) should be quite trivial.
GREAT!
* extra table
There is an extra table in the database (physmessage, for 'physical
message', as opposed to virtual message) which links messageblocks and
messages. This gives us great speed up with regard to copying messages.
In the old database scheme, copying a message meant copying all
messageblocks, which is slow. Now, only a new entry in the messages
table has to be made, which points to the same physmessage record.
This speed up was needed because copying occurs quite frequently; IMAP
has no MOVE command, so a move is done by a COPY followed by a delete.
This occurs often, for instance when a client does not really delete,
but moves a message to the Trash folder
The messages tables has been changed like this: it holds an extra
physmessage_id field. The messagesize, rfcsize and internal_date fields
have
been removed.
the physmessage table holds: messagesize, rfcsize and internal_date
the messageblks table now holds a physmessage_id instead of a message_idnr
This is probably a stupid question, but:
I do not understand the database structure now, can someone
please clarify the operation.
You have several database definitions, where you state FOREIGN
KEY ... REFERENCES ... ON DELETE CASCADE.
This is in the innodb part.
Well suppoe I do a move from folder A to folder B.
The record in the messages table is copied to also reference
folder B.
Next the message record that references folder A is deleted,
Well everything works all right, because the physmessage does not
contain a foreign key reference.
But what happens if an ordinary user choses to actually delete a
message. How do you know that it is not referenced anywhere else?
How do you delete messageblks records?
I remember some discussion we had about compressing the content
by having just one unique message block earlier, this should be
somewhat feasible to the body part of the message.
/Magnus
