Function ThereIsAtLeastOneRole

src/backend/utils/init/postinit.c:1753–1769

* Returns true if at least one role is defined in this database cluster. */

 * Returns true if at least one role is defined in this database cluster.
 */
static bool
ThereIsAtLeastOneRole(void)
{
	Relation	pg_authid_rel;
	TableScanDesc scan;
	bool		result;

	pg_authid_rel = table_open(AuthIdRelationId, AccessShareLock);

	scan = table_beginscan_catalog(pg_authid_rel, 0, NULL);
	result = (heap_getnext(scan, ForwardScanDirection) != NULL);

	table_endscan(scan);
	table_close(pg_authid_rel, AccessShareLock);

	return result;
}