Database superuser have more privileges than normal users. They can call some functions such as datalink.curl_get().
Also, they bypass some permission checks done for normal users.
Normal users can read existing files if they have SELECT privilege on directory or the datalink is linked with READ ACCESS DB option.
Normal users can create new files if they have CREATE privilege on directory.
All users require DELETE privilege on appropriate directory to be able to delete files with ON UNLINK DELETE option.
Exploded permissions for directories are in updatable view datalink.access.
Database administrator can INSERT/UPDATE/DELETE individual privileges here.
Currently supported directory privileges:
SELECT- read filesCREATE- create new filesDELETE- delete filesREFERENCES- reference files (not implemented yet)
Granting a DELETE privilege to current user:
mydb=# insert into datalink.access values ('/var/www/datalink/','delete',user);
INSERT 0 1