Theo Schlossnagle wrote:


On Feb 20, 2007, at 1:40 PM, Tom Lane wrote:

RPK <[EMAIL PROTECTED]> writes:
I did not mean asking for undo from a life-time log. Since FlashBack
Technology is already there, I just mean that world's most advanced database
(PostgreSQL, as they say), must have an optimized way for undoing of at
least a week changes.

You're living in a dream world.  Do you know any Oracle DBs who keep
enough rollback segments to go back a week?

Ours go for a good 6 hours sometimes :-D

Eeven if it's just one hour, it's certainly better than nothing.
I fully agree that I'd not be acceptable to introduce performance
problems for _everyone_ by introducing flashback. But if you only
experience a drop in performance if you actually enable flashback
(by, let's say setting vacuum_min_deadtime=1h), then I don't see
why anyone would object to having support for some kind of flashback.

However, I just realized that doing this is much harder than I initially
thought, because catalog access always happens with SnapshotNow, and
e.g. "drop table" deletes datafiles at commit time, and not during vacuum.

Supporting "begin; drop table mytable; commit; begin; set transaction flashback 1 hour; select * from mytable; commit" would therefore be
really hard...

greetings, Florian Pflug

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