This patch record was "closed for lack of interest", but I think what's actually needed is committer review of which approach to take.
- add backend functions but do not modify psql ? - add to psql slash-plus commnds ? - introduce psql double-plus commands for new options ? - change pre-existing psql plus commands to only show size with double-plus ? - go back to the original, two-line client-side sum() ?
Until then, the patchset is organized with those questions in mind.
