[horde] Share performance problem

[Janne Peltonen]

Hi!

We recently upgraded our old horde/IMP installation to the new Groupware
edition (1.1.1). Everything appeared okay, but when we let our 1500+
concurrent users (of abt 40000 total users) in, our database server
(4x2GHz CPU, 4GB mem, intel 32 bit arch, mysqld 5.0.62) went onto its
knees. I've read through this thread:

  http://lists.horde.org/archives/dev/Week-of-Mon-20080609/023105.html

and we had the same problem, namely, the mysql queries including bitwise
operations taking incredibly long to complete on a mysqld server. (And
we have done every optimisation we could find, and were of course using
the native sql share driver) See this message:

  http://lists.horde.org/archives/dev/Week-of-Mon-20080609/023122.html

Similar queries to the one given there (or rather, in the previous
message) took abt 45 seconds to complete. And there were such queries,
even when we had completely disabled sharing.

At the end, we had to change the _getShareDescription method in the
Share sql backend to only return a simplistic search in the share table
that only returns the shares that are owner by the user. That way, we
could get rid of the bitwise and operations (which, according to the
message linked above, are the real culprit). And our installation began
to fly... (the simpler version of the query took less than a second when
the mysql server was on its knees, and only a couple milliseconds when
it had gotten rid of the monstrous queries).

So, two questions:

1) Does anyone have any ideas on how to optimize the kind of SQL queries
mentioned in the message? We'd like to enable sharing of calendars and
address books one day again, but with these loads it appears
impossible...

2) Why is it that even when sharing, even of addressbooks, is disabled
(there is an empty string as the share backend in conf.php), such
expensive queries are still generated?

We'd really like to be able to use Kronolith as a group calendar, but as
it is, it appears impossible...


Thanks for any input!

--Janne Peltonen
Univ. of Helsinki
-- 
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