This does not happen every time, unfortunately. I've tried to google this issue - 've found similar problems, but most of them revolve around MariaDB 5 series with OQGRAPH v2, not v3.
Create a test database with the information listed here:
It takes over a minute for it to return "Killed", all the while mysqld uses as much CPU as possible. But then, if I try to access it again:
And then sometimes, it works as expected.
Accessing from PHP or Python has the same effect: 100% CPU load. I've yet to get a proper result returned from these environments.
Selecting from oq_backing works fine.
MariaDB 10.0.8 (query cache disabled)