On 13.02.25 14:06, jian he wrote:
> I didn't solve the out join semantic issue.
> i am wondering, can we do the virtual generated column expansion in
> the rewrite stage as is,
> and wrap the expressions in PHVs if the virtual generated
> columns come from the nullable side of an outer join.
PlaceHolderVar looks like a fitting mechanism for this. But it's so far
a planner node, so it might take some additional consideration if we
want to expand where it's used.
Maybe a short-term fix would be to error out if we find ourselves about
to expand a Var with varnullingrels != NULL. That would mean you
couldn't use a virtual generated column on the nullable output side of
an outer join, which is annoying but not fatal, and we could fix it
incrementally later.
