The guilty part of the test checks for performance degradation on
a query with numerous joins on an empty table. The test expects
the query to take less than 1 second, and fails if it is not so
(which can happen on very slow builders).

The solution is to add more JOINs to the query. On a fixed server,
it should not have any noticeable impact on the query execution,
while on the unfixed version the query would take several times
longer (e.g. 6.5 sec vs 1.5 sec). Thus, we can increase the margin
for the error, and make the test fail when the query takes longer
than 5 seconds.