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List:       kmail-devel
Subject:    Re: for kmail people: a discussion of mail summary files
From:       Don Sanders <don () sanders ! org>
Date:       2000-05-16 4:39:46
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KMail uses this format for storing mails. There is a lot of wasted space at the
moment but I'm cautious about clean it up as it will inconvenience users and
only save disk space and not much RAM.

Oh, KMail does have one weakness when changing the status of messages it does
not update the mail folder on disk, so when the index is recreated the status
information is lost.

The main problem with this format is that it is slow to transfer mails from one
folder to another.

The main benefit of this format is that messages are stored as plain text, so
you can grep folders.

The idea of storing MD5 hashes of message ids instead of the actual message ID
had occurred to me and has been talked about on the KMail mailing list for some
time but I haven't got around to doing it yet.

It does sound like his methods are very fast (15,466 messages in under a second
is excellent). Something that takes up a lot of time in KMail when showing a
list of message headers (if not taiking up the most time) is the cost of
operator new. A KMMsgInfo object and a QListViewItem object has to be
constructed for each message header in the list. This means a lot of calls to
operator new which is very slow. I tried to speed this up by recycling
QListViewItems instead of deleting them and creating new ones this helped a lot
but I never really finished this work. (Trying changing from one folder to
another folder with the same number of messages in KMail and compare that to
the speed of changing from an empty folder back to the same folder. It will be
much faster when folders have the same number of messages.).

I guess I could recycle KMMsgInfo objects too, that's an idea. Also perhaps I
could define my own operator new method, I've never done that before.


Making KMail faster is not the main priority right now, a search dialog and and
an improved address book is. After that IMAP support and non-blocking SMTP is
tops. Say does anyone know if the IMAP kioslave works? Last I heard it didn't.  


On Tue, 16 May 2000, pbrown@redhat.com wrote:
> Jamie Zawinski gives a great deal of insight into mail summary files and
> indexing mbox in general:
> 
> http://www.jwz.org/doc/mailsum.html
> 
> -- 
>   Preston Brown
>   pbrown@redhat.com                                Red Hat, Inc.

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