Re: INSERT ... ON CONFLICT UPDATE and RLS

Another issue that I see is that there is only one resultRelation
between the INSERT and UPDATE. That means that without some additional
special measure, both UPDATE and INSERT "WITH CHECK ( ... ) " options
are applied regardless of whether the INSERT path was taken, or the
UPDATE path. Maybe that's actually sensible (note that even this
doesn't happen right now, since the auxiliary UPDATE is currently
minimally processed by the rewriter). What do people think about that?
It seems like it might be less surprising to have that fail earlier
when there are separate policies for INSERT and UPDATE -- for UPSERT,
all policies are applied regardless of which path is taken.

The task of making the security qual enforced like a check option
before we go to update a locked row (at the start of the UPDATE path,
for any UPDATE policy with a USING security qual) looks complicated.
I'd appreciate a little help on the implementation details.

Apparently Oracle does not offer "fine-grained access control" with
MERGE, which I believe means they just don't support this kind of
thing at all. Obviously I'd rather avoid that here, but the correct
semantics are not obvious. ON CONFLICT UPDATE could almost justify
making CREATE POLICY FOR INSERT accept a USING expression, since
that's really where the row to UPDATE comes from.
--
Peter Geoghegan