Function create_foreign_join_path

src/backend/optimizer/util/pathnode.c:3699–3744

* create_foreign_join_path * Creates a path corresponding to a scan of a foreign join, * returning the pathnode. * * This function is never called from core Postgres; rather, it's expected * to be called by the GetForeignJoinPaths function of a foreign data wrapper. * We make the FDW supply all fields of the path, since we do not have any way * to calculate them in core. However, there

 * the pathtarget (rel->reltarget), so we let a NULL for "target" select that.
 */
ForeignPath *
create_foreign_join_path(PlannerInfo *root, RelOptInfo *rel,
						 PathTarget *target,
						 double rows, Cost startup_cost, Cost total_cost,
						 List *pathkeys,
						 Relids required_outer,
						 Path *fdw_outerpath,
						 List *fdw_private)
{
	ForeignPath *pathnode = makeNode(ForeignPath);

	/*
	 * We should use get_joinrel_parampathinfo to handle parameterized paths,
	 * but the API of this function doesn't support it, and existing
	 * extensions aren't yet trying to build such paths anyway.  For the
	 * moment just throw an error if someone tries it; eventually we should
	 * revisit this.
	 */
	if (!bms_is_empty(required_outer) || !bms_is_empty(rel->lateral_relids))
		elog(ERROR, "parameterized foreign joins are not supported yet");

	pathnode->path.pathtype = T_ForeignScan;
	pathnode->path.parent = rel;
	pathnode->path.pathtarget = target ? target : rel->reltarget;
	pathnode->path.param_info = NULL;	/* XXX see above */
	pathnode->path.parallel_aware = false;
	pathnode->path.parallel_safe = rel->consider_parallel;
	pathnode->path.parallel_workers = 0;
	pathnode->path.rows = rows;
	pathnode->path.startup_cost = startup_cost;
	pathnode->path.total_cost = total_cost;
	pathnode->path.pathkeys = pathkeys;
	if (Gp_role == GP_ROLE_DISPATCH)
	{
		make_cdbpathlocus_for_foreign_relations(root, rel, pathnode);
	}
	else
	{
		/* make entry locus for utility role */
		CdbPathLocus_MakeEntry(&(pathnode->path.locus));
	}
	pathnode->fdw_outerpath = fdw_outerpath;
	pathnode->fdw_private = fdw_private;

	return pathnode;
}

/*
 * create_foreign_upper_path