Re: Alter timestamp without timezone to with timezone rewrites rows

On Wed, Jan 13, 2021 at 10:28:26AM -0500, Tom Lane wrote:
> So a non-rewriting conversion would only be possible if local time is
> identical to UTC; which is true for few enough people that nobody has
> bothered with attempting the optimization.

PostgreSQL 12 and later do have that optimization.  Example DDL:
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=3c59263#patch4