> which "it would come in handy" wouldn't have enabled it. (FWIW this
> feature used to exist in the Berkeley code, under the cool name "time
> travel", and was removed a long time ago.)
No, it didn't AFAIK. Timetravel kept all tuples in the database with all
indexes and constraints active at all time. That's not the case with the
flashback technology. You put aside some storage space that you don't need
for something else. When that space is spent, tuples start dropping off the
edge.
I've talked to people who was very much happy with this feature. Mostly DBA's
recovering from their own stupid mistakes of course :-)
But yes, it has to be enabled, and yes it has to have a performance cost
somehow, but people are requesting it, and somehow I don't think Oracle
developed the feature just for fun. If you plug into Postgres' vacuum it
would be rather cheap to make, I recon. I wouldn't worry about query speed as
I guess that the use cases for retrieving already deleted rows don't aren't
performance dependant.
--
Med venlig hilsen
Kaare Rasmussen, Jasonic
Jasonic Telefon: +45 3816 2582
Nordre Fasanvej 12
2000 Frederiksberg Email: kaare@jasonic.dk