UPSERT wiki page, and SQL MERGE syntax

Having been surprisingly successful at advancing our understanding of
arguments for and against various approaches to "value locking", I
decided to try the same thing out elsewhere. I have created a
general-purpose UPSERT wiki page.

The page is: https://wiki.postgresql.org/wiki/UPSERT

Right now, I would like to address the less contentious but still
unresolved question of whether or not we should use the SQL-standard
MERGE syntax instead of the non-standard INSERT ... ON CONFLICT UPDATE
syntax that my patch proposes.

Note that I'm trying to direct the conversation along certain lines:
Is MERGE the right syntax for this particular effort ("UPSERT")? And,
in particular, not: Is SQL MERGE useful? I think that it is useful,
but is a largely unrelated feature.

Please correct the Wiki page if I have failed to credit SQL MERGE with
some advantage that someone stated at some point. I don't recall any
arguments for it, other than that it is in the SQL standard, but maybe
I missed one.

In general, add to this page, and edit it as you see fit. It'll be
useful to centralize the references, discussion and state of the patch
in one agreed upon place, as the patch continues to evolve.
--
Peter Geoghegan