If you want to track the extent to which customers submit multiple tickets (possibly a good barometer for CSAT, product quality and/or help site effectiveness) you can give this report a try. It has two custom queries:
In the 'What' section of the GoodData config screen for this report, there are two parameters, both of which are based on custom metrics. For info on creating custom metrics, please see page 140 of the attached PDF.
First custom metric
The first custom metric has been titled "> 1 Ticket". Here's the MAQL for this Report-Specific Metric:
SELECT (SELECT # Submitters WHERE (SELECT # Tickets BY Submitter ) > 1) / # Submitters
Second custom metric
The second custom metric has been titled "Submitters". Here's the MAQL for this Global Metric:
SELECT COUNT (Submitter, Ticket Id)
Building metrics and queries in GoodData has a learning curve; if you have trouble, I suggest reaching out to their Support team for assistance. I've had really good experiences with their team.