Error while using module

Hello,

I'm using RokSproket module that came with JP Pasta in several instances on this site: inforegio.net/inforegio/
You can see two error messages that are generated by two instances, Features and Mosaic. Basically, when I have 4 stories in Features it is ok, but if I add 5th it shows this error. Similar thing for Mosaic. Both of them have only few entries.
If I'm not mistaken, the error is generated by server.
Site is on shared hosting. Php version 5.6.18. In PhpMyAdmin I can see that Join buffer size is set to 6 MiB and Max join size is set to 20,000,000 and both are set by provider.
I think that I should use SET SQL_BIG_SELECTS=1, but I'm not sure where to add this line.

Thanks,
Sasa

stackoverflow.com/questions/22630238/err...or-set-max-join-size