BTW, it seems like there is consensus that we ought to reorder the items
in a jsonb object to have keys first and then values, independently of the
other issues under discussion. This means we *will* be breaking on-disk
compatibility with 9.4beta2, which means pg_upgrade will need to be taught
to refuse an upgrade if the database contains any jsonb columns. Bruce,
do you have time to crank out a patch for that?
regards, tom lane