/usr/lib/ghc-doc/hoogle/postgresql-libpq.txt is in libghc-postgresql-libpq-doc 0.8.2.1-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-postgresql-libpq-doc/html/postgresql-libpq.txt