CREATE OR REPLACE FUNCTION get_data_from_server()
 RETURNS SETOF sometype AS
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declare
    connx text;
    tempval text;
    rs record;
    result sometype;
begin
    for rs in select server_ip_address,ist_id from ip_server_table
    loop

        SELECT (extract(year from localtimestamp)::text || extract(month  from localtimestamp) || extract(day from localtimestamp) || extract(hour from localtimestamp)  || extract(minute from localtimestamp) || extract(second from localtimestamp)  || extract(ms from localtimestamp) ) || ist_id INTO connx;
        select into tempval dblink_connect(connx, 'hostaddr=' || rs.server_ip_address || ' dbname=somedatabase user=someuser password=somepassword port=5432');
        if tempval = 'OK' then
            --fetch data
        end if;

    end loop;
end;
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  LANGUAGE plpgsql VOLATILE;