Re: Proposal: Select ... AS OF Savepoint

On 11/2/07, Hans-Juergen Schoenig <postgres(at)cybertec(dot)at> wrote:
>
>
> I think Simon Riggs is already working on that idea. This one is fairly
> easy to implement. I think these are some of the features only a time-stamp
> based database can implement. I think database standards were formed during
> the time, when the data consistency was provided with Lock based mechanisms.
> And moreover i have already committed on the indexes with snapshot and i am
> still waiting for its approval from hackers. If that does go through, then
> i need to work on the reverse mapping hash tables, which is really a long
> task. So i may not be able to take up time-travel now.
>
>
>
> if i remember my last talk with Simon correctly the idea is to have
> timetravel across transactions.
> having this feature inside a transaction will not make it into CVS as it
> is basically of no practical use.
>

I am just reminding my days of working with Oracle. The Flashback feature
was allowed only for DBAs, and they never let the developers access that
feature, unless there is a strong reason for it. It was more thought of as a
feature for recovery and they never let deveopers use that in the
application. Also it was designed as a optional feature. If its switched
off, it cannot be used. If someone comes up with the time travel feature
across transactions and if it is designed as non-optional feature and if it
happens to be a feature, which DBA can let the developers use freely, then
this feature should be rolled back. The feature i am talking about is very
simple and it won't even add 100 lines of code into the Postgres source code
base.

i would suggest to put some effort into making it work across transactions.
> just saving the snapshot is not enough
> here - there are a couple of other things which have to be taken into
> consideration (transaction wraparound, etc.)
>

When i think about it, Timetravel always look big for me and i don't have
the bandwidth to take that up.

if you want to work on timetravel my team and i can provide some assistance
> as we wanted to help in this area anyway.
>

Thanks. Please send me your findings.

--
Thanks,
Gokul.
CertoSQL Project,
Allied Solution Group.
(www.alliedgroups.com)