Hi, I am playing with this plugin at the moment also.
I'm not sure about your database queries but the plugin collects data overnight. To get mine to run I manually ran the cron (as it wasn't auto on my test server) then did the following as stated on the Gismo website...
IMPORTANT: FIRST RUN OF THE DATA EXPORTER: Gismo needs to perform some computation on regular basis. The purpose of this computation is to extract data from logs and derive aggregated information. This computation is done daily by a script that, depending on the setting of your
Moodle cron script, runs during the night between 02.00 and 04.00 (server time).
When you install the Gismo software the fist time, if you don't want to wait
the next day to see the result, you can lunch this script by hand
at this address:
did you try that?
I notice it doesn't include the new (2.4) assignments in its data but its seems pretty great so far in testing. The developers reckon they will make a 2.5 version sometime between July and Sept 2013 so that will be good.
Let me know how your testing goes! Did you look at MOCLog also as that seems to be a global analytical tool ( I haven't installed that yet)