On Wed, 28 Apr 2010 16:47:10 +0100, Ron White <exim.ml@???> wrote:
> As my ACL grows It has crossed my mind that for every acl stanza making
> use of a MySQL that fires off, there is the roundtrip cost of the query.
> Whilst some of the lookups can be optimised by ACL layout, I'm not going
> to be able to avoid some similar very similar queries when I check my
> database for certain flags being set on a per user basis.
Please do note that for exactly similar - ie. identical :) - queries in
the same message session, Exim will cache the results anyway:
http://www.exim.org/exim-html-current/doc/html/spec_html/ch09.html#SECID64
I've built a few systems which handle a relatively large volume (ie.
>100000 messages/day being delivered) which use MySQL, and in all cases the
database itself has not been a bottleneck.
If you run a mock SMTP session as follows:
exim -d+all-memory -bh [insert valid IP here] 2>&1 | tee session.out
...then input all the relevant EHLO/HELO, MAIL FROM and RCPT TO commands
followed by DATA with a valid message, you'll get all the debug output in
the file session.out. This should let you check just how (sub)optimal your
query formation is - what you're looking for are lines like this:
02:45:30 32556 cached data used for lookup of SELECT dir FROM etable WHERE
name='graeme@???' limit 1
ooh, I saved myself a single query ;-)
Graeme
