/usr/share/postgresql/10/extension/citus--5.0-2--5.1-1.sql is in postgresql-10-citus 7.0.3.PGDG-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | /* citus--5.0-2--5.1-1.sql */
/* empty, but required to update the extension version */
|