On 8/28/12 2:51 PM, Pavel Stehule wrote:
>> >The thing I don't like about this is it assumes that time is the best way to
>> >refer to when things changed in a system. Not only is that a bad assumption,
>> >it also means that relating things to history becomes messy.
> On second hand I don't have a problem with some optional counter,
> although I think so database system time is very useful and other
> counters for versioning are not necessary - because in one time I can
> have only one version - it doesn't do versions from rollbacked
> transactions.
What happens if the system clock runs backwards?
What happens if two transactions start in the same microsecond? (And I know for a fact that's possible, because I've
seenit).
More importantly, I believe using time to handle recording a versioned history of something is flawed to begin with.
Youmight care about what time a new version was created; but what's far more important is recording the correct
orderingof things, and time isn't actually a great way to do that.
Note that no version control systems use time as their primary attribute.
--
Jim C. Nasby, Database Architect jim@nasby.net
512.569.9461 (cell) http://jim.nasby.net