Function getLockedRefname

src/backend/parser/parse_relation.c:2737–2774

* Has the specified refname been selected FOR UPDATE/FOR SHARE? * * This is used when we have not yet done transformLockingClause, but need * to know the correct lock to take during initial opening of relations. * * Note: we pay no attention to whether it's FOR UPDATE vs FOR SHARE, * since the table-level lock is the same either way. */

 * since the table-level lock is the same either way.
 */
LockingClause *
getLockedRefname(ParseState *pstate, const char *refname)
{
	ListCell   *l;

	/*
	 * If we are in a subquery specified as locked FOR UPDATE/SHARE from
	 * parent level, then act as though there's a generic FOR UPDATE here.
	 */
	if (pstate->p_lockclause_from_parent)
		return pstate->p_lockclause_from_parent;

	foreach(l, pstate->p_locking_clause)
	{
		LockingClause *lc = (LockingClause *) lfirst(l);

		if (lc->lockedRels == NIL)
		{
			/* all tables used in query */
			return lc;
		}
		else
		{
			/* just the named tables */
			ListCell   *l2;

			foreach(l2, lc->lockedRels)
			{
				RangeVar   *thisrel = (RangeVar *) lfirst(l2);

				if (strcmp(refname, thisrel->relname) == 0)
					return lc;
			}
		}
	}

	return NULL;
}

/*
 * isSimplyUpdatableRelation