Here's a version of this rebased up to HEAD, fixing a couple of trivial merge conflicts and incorporating the docs delta I posted separately.
(I'd supposed this patch was still OK because the patch tester said so,
but I now see that the tester was only testing the docs delta :-(.)
regards, tom lane
use-dtype-rec-for-all-composites-3.patch.gz
Description: use-dtype-rec-for-all-composites-3.patch.gz
