I am looking at a database with a wide (~500G) divergence between the total space expended by the database directory and the result of select sum(pg_relation_size(oid)) from pg_class;.
I located about 280G of apparent extra space by performing an anti-join between files on disk and files in the catalog via the pg_class.relfilenode field.
What should I do to get rid of the data, if it is, in fact, "extra"? Is there a reasonable bug report to file? Can I independently compute the entire itemization of files that belong in the data directory?
The cluster was pg_upgrade'd, in link mode, a while ago, to 10.1 from 9.6. This is not necessarily relevant, though.
Thanks,
Daniel