I have received this error:
Bad SQL query Incorrect key file for table '/tmp/#sql_659_0.MYI'; try to repair it
So, following this suggesttion, I try to edit:
sort_buffer_size=4M
join_buffer_size=4M
But I can not find them. Where are they located on Ubuntu 14.04 machine? There are no such options in /etc/mysql/my.cnf