Re: Clarification on a Time travel feature

hello ...

i guess there is no formal proposal yet but there are some ideas
around and some major challenges have been discussed already.
i think simon riggs was planning to work on it in the future.
the basic idea here is to have the option to create a "snapshot"
which then stays in the database. the main challenge is that PostgreSQL
should not keep all version of a row since the snapshot but VACUUM
should be able to clean out all rows which are not seen by any
snapshot or any ongoing transaction.
this should be a quite fancy solution which is quite space efficient.

internally we had the idea of tweaking VACUUM a little:

VACUUM BEFORE timestamp;
and ...
SET current_snapshot TO '2007-10-10 ...';

this would allow a queries to use any snapshot after the timestamp
defined by VACUUM (if data is around).
the downside here: you might potentially eat up more space.
flashback data should be read only, of course.

best regards,

hans

On Oct 31, 2007, at 11:31 AM, Gokulakannan Somasundaram wrote:

> Hi,
> I went through the mailing list and couldn't get answer to the
> question.
>
> a) Is there a proposal in place for going back in time within a
> transaction?
>
>
>
> --
> Thanks,
> Gokul.
> CertoSQL Project,
> Allied Solution Groups.
> (www.alliedgroups.com)

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