Function create_gather_path

src/backend/optimizer/util/pathnode.c:3003–3036

* create_gather_path * Creates a path corresponding to a gather scan, returning the * pathnode. * * 'rows' may optionally be set to override row estimates from other sources. */

 * 'rows' may optionally be set to override row estimates from other sources.
 */
GatherPath *
create_gather_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
				   PathTarget *target, Relids required_outer, double *rows)
{
	Assert(false);
	GatherPath *pathnode = makeNode(GatherPath);

	Assert(subpath->parallel_safe);

	pathnode->path.pathtype = T_Gather;
	pathnode->path.parent = rel;
	pathnode->path.pathtarget = target;
	pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
														  required_outer);
	pathnode->path.parallel_aware = false;
	pathnode->path.parallel_safe = false;
	pathnode->path.parallel_workers = 0;
	pathnode->path.pathkeys = NIL;	/* Gather has unordered result */

	pathnode->subpath = subpath;
	pathnode->num_workers = subpath->parallel_workers;
	pathnode->single_copy = false;

	if (pathnode->num_workers == 0)
	{
		pathnode->path.pathkeys = subpath->pathkeys;
		pathnode->num_workers = 1;
		pathnode->single_copy = true;
	}

	cost_gather(pathnode, root, rel, pathnode->path.param_info, rows);

	return pathnode;
}

/*
 * create_subqueryscan_path