Re: Postgres_fdw join pushdown - wrong results with whole-row reference

I wonder whether such a whole-row-var would arise from the nullable side
of a join? I guess not.  Not that I'm saying we shouldn't account for that
case at all since any and every whole-row-var in the targetlist currently
gets that treatment, even those that are known non-nullable. Couldn't we
have prevented the latter somehow?  IOW, only generate the CASE WHEN when
a Var being deparsed is known nullable as the comment there says:

deparse.c:

1639 /*
1640  * In case the whole-row reference is under an outer join then it has
1641  * to go NULL whenver the rest of the row goes NULL. Deparsing a join
1642  * query would always involve multiple relations, thus qualify_col
1643  * would be true.
1644  */
1645 if (qualify_col)
1646 {
1647     appendStringInfoString(buf, "CASE WHEN");
1648     ADD_REL_QUALIFIER(buf, varno);
1649     appendStringInfo(buf, "* IS NOT NULL THEN ");
1650 }

But I guess just fixing the expression as your patch does may be just fine.