Could it be an idea to also add OUT can_be_zero boolean
to pg_get_catalog_foreign_keys()'s out parameters? This information is useful to know if one should be doing an INNER JOIN or a LEFT JOIN on the foreign keys. The information is mostly available in the documentation already, but not quite accurate, which I've proposed a patch [1] to fix. [1] https://www.postgresql.org/message-id/4ed9a372-7bf9-479a-926c-ae8e77471...@www.fastmail.com
