Hi Folks,
Does anyone have any insight into what user mailbox stores look like
for yahoo, gmail, hotmail, etc? I am curious if they have, e.g. a
mailbox table for each user that contains all their email or whether
they have a single large table with email for all users or whether
they have a smaller subset of tables with the users distributed
between them? Each user can have a large number of messages, so a
single table would end up having billions of records (for one of these
webmail systems with millions of users) and likewise you wouldn't want
separate tables for each user because then you'd have millions of
tables. Any thoughts? Thanks.
Sean

meranayaghar (AT) yahoo (DOT) com wrote:
tables and SQL and DDL) to store messages for such large user bases, the
overheads would be too great. Having said that, of course if when a
user authenticates you direct it to a particular (set of) server(s), you
would be able to do it.

Early on-line mail services used bog-standard email systems underneath,
usually an IMAP variant - see <http://www.imap/org> to begin learning
far more than you want to about IMAP - of which some implementations use
an underlying database, but most are file-store based.

Gmail probably uses the Google file system.

Squirrelmail, which may be the commonest webmail interface in the world,
sits on top of IMAP, see above for what can be below that.

Once upon a time, mentioning storing mail in a database would stir up a
veritable hornets nest in the various comp.mail.* newsfroups, nowadays
you might cop as much as, "Well, if you want to, I'm not going to waste
my breath telling you why it's a bad idea."[1]

Cheers,
Gary B-)

1 - Why do some people consider using a database to store email a bad idea?

Here is an example, view it in the context of a very large (corporate or
academic) user base, who expect to be able to retrieve messages they
have mistakenly deleted, and assume that messages they received 20+
years ago are still available to them.

Consider the problem of restoring *one* user's messages from backup.

It is trivial in relation to a file-store "pull this directory tree from
the tape and put it over there, so the user can examine it at heeshes
leisure".

With a database, "restore table X from the backup media" is/was either
not available, or an expensive add-on. And as for "restore table X but
keep anything currently there" - I can't say I've seen that one
anywhere, but I could be wrong.

Same for "restore this related group of tables."

And "select all messages from mirror-database where user = 'xyz'" just
won't work!

Cheers,
Gary B-)

--
__________________________________________________ ____________________________
Armful of chairs: Something some people would not know
whether you were up them with or not
- Barry Humphries

On 02.05.2009 07:35, Gary R. Schmidt wrote:

Oracle Flashback comes to mind.

Kind regards

robert

Robert Klemme wrote:

Cheers,
Gary B-)

On May 1, 10:35*pm, "Gary R. Schmidt" <grschm... (AT) acm (DOT) org> wrote:
Thanks Gary. What you say above makes a lot of sense, the idea of
storing all user email in databases does seem a might untenable.
Sean