Function CheckForModifySystemFunc

src/backend/commands/functioncmds.c:2686–2694

}

static void
CheckForModifySystemFunc(Oid funcOid, List *funcName)
{
	if (!allowSystemTableMods && funcOid < FirstBootstrapObjectId)
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission defined: \"%s\" is a system function",
						NameListToString(funcName))));
}

/*
 * Execute CALL statement