Auto Upgrade
-----------------
file conversion should be done automatically when the new engine connects.  

auto-upgrade application:
check if new version is available 
(option: digital signature)
if yes download new version
(option: http, https, ftp)
backup database to SQL script
(option: list of databases, use recovery mechanism)
install new version

ftp client
task to download new version from another HTTP / HTTPS / FTP server
multi-task


Direct Lookup
-----------------
drop table test;
create table test(id int, version int, idx int);
@LOOP 1000 insert into test values(1, 1, ?);
@LOOP 1000 insert into test values(1, 2, ?);
@LOOP 1000 insert into test values(2, 1, ?);
create index idx_test on test(id, version, idx);
@LOOP 1000 select max(id)+1 from test;
@LOOP 1000 select max(idx)+1 from test where id=1 and version=2;
@LOOP 1000 select max(id)+1 from test;
@LOOP 1000 select max(idx)+1 from test where id=1 and version=2;
@LOOP 1000 select max(id)+1 from test;
@LOOP 1000 select max(idx)+1 from test where id=1 and version=2;
-- should be direct query
