/usr/lib/x86_64-linux-gnu/libmysqlclient_r.so.18 is in libmysqlclient18 5.5.54-0ubuntu0.12.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18
/usr/lib/x86_64-linux-gnu/libmysqlclient.so.18