Each time a file is created in Moodle mdl_files table, there is an extra entry created there - the current "." directory. This means for example that for each Moodle file resource, there are 2 entries created in mdl_files table.
This introduces some unnecessary overhead in big Moodle sites. I've seen Moodle sites with millions of file resources. So for the site with 10 million file resources, mdl_files will have 20 million entries - 50% of them redundant ones (not bringing any new information into the database).
I've implemented a patch to change see - please see https://tracker.moodle.org/browse/MDL-65857 . Any comments (and help!) welcome!