/usr/lib/ghc-doc/hoogle/hsql-mysql.txt is in libghc-hsql-mysql-doc 1.8.2-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-hsql-mysql-doc/html/hsql-mysql.txt