Génère un événement SYNC si aucun n'a eu lieu dans l'interval requis.

declare
        p_interval     alias for $1;
        v_node_row     record;

BEGIN
        select 1 into v_node_row from sl_event 
          where ev_type = 'SYNC' and ev_origin = getLocalNodeId('schemadoc')
          and ev_timestamp > now() - p_interval limit 1;
        if not found then
                -- If there has been no SYNC in the last interval, then push one
                perform createEvent('schemadoc', 'SYNC', NULL);
                return 1;
        else
                return 0;
        end if;
end;