Function preprocess_rowmarks

src/backend/optimizer/plan/planner.c:2903–3009

* preprocess_rowmarks - set up PlanRowMarks if needed */

 * preprocess_rowmarks - set up PlanRowMarks if needed
 */
static void
preprocess_rowmarks(PlannerInfo *root)
{
	Query	   *parse = root->parse;
	Bitmapset  *rels;
	List	   *prowmarks;
	ListCell   *l;
	int			i;

	if (parse->rowMarks)
	{
		/*
		 * We've got trouble if FOR [KEY] UPDATE/SHARE appears inside
		 * grouping, since grouping renders a reference to individual tuple
		 * CTIDs invalid.  This is also checked at parse time, but that's
		 * insufficient because of rule substitution, query pullup, etc.
		 */
		CheckSelectLocking(parse, linitial_node(RowMarkClause,
												parse->rowMarks)->strength);
	}
	else
	{
		/*
		 * We only need rowmarks for UPDATE, DELETE, or FOR [KEY]
		 * UPDATE/SHARE.
		 */
		if (parse->commandType != CMD_UPDATE &&
			parse->commandType != CMD_DELETE)
			return;
	}

	/*
	 * We need to have rowmarks for all base relations except the target. We
	 * make a bitmapset of all base rels and then remove the items we don't
	 * need or have FOR [KEY] UPDATE/SHARE marks for.
	 */
	rels = get_relids_in_jointree((Node *) parse->jointree, false);
	if (parse->resultRelation)
		rels = bms_del_member(rels, parse->resultRelation);

	/*
	 * Convert RowMarkClauses to PlanRowMark representation.
	 */
	prowmarks = NIL;
	foreach(l, parse->rowMarks)
	{
		RowMarkClause *rc = lfirst_node(RowMarkClause, l);
		RangeTblEntry *rte = rt_fetch(rc->rti, parse->rtable);
		PlanRowMark *newrc;

		/*
		 * Currently, it is syntactically impossible to have FOR UPDATE et al
		 * applied to an update/delete target rel.  If that ever becomes
		 * possible, we should drop the target from the PlanRowMark list.
		 */
		Assert(rc->rti != parse->resultRelation);

		/*