Re: Switching PL/Python to Python 3 by default in PostgreSQL 12

I wrote:
> But I could support having a way for individual installations to change
> what the synonym means locally. Perhaps we could think about how to do
> that in conjunction with the project of getting rid of pg_pltemplate
> that's been kicked around before [1][2][3].

... actually, if we had that (i.e., languages fully defined by extensions
with no help from pg_pltemplate), wouldn't this be nearly trivial?
I'm imagining two extensions, one that defines plpythonu to call the
python2 code and one that defines it to call the python3 code, and you
install whichever you want. They're separate from the extensions that
define plpython2u and plpython3u, so mix and match as you wish.

regards, tom lane