Re: New feature request: FlashBack Query

Hannu Krosing wrote:
> Ühel kenal päeval, P, 2007-02-18 kell 14:27, kirjutas Joshua D. Drake:
>> Hannu Krosing wrote:
>>> Ühel kenal päeval, L, 2007-02-17 kell 22:49, kirjutas Chad Wagner:
>>> To get a flashback query, you "just" have to construct a snapshot from
>>> that time and you are done. We don't store transaction times anywere, so
>>> the flashback has to be by transaction id, but there is very little
>>> extra work involved. We just don't have syntax for saying "SELECT ... AS
>>> SEEN BY TRANSACTION XXX"
>> Well this is certainly interesting. What do we think it would take to
>> enable the functionality?
>
> First we must run the query in serializable mode and replace the
> snapshot with a synthetic one, which defines visibility at the start of
> the desired transaction
>
> probably it is a good idea to take a lock on all tables involved to
> avoid a vacuum to be started on them when the query is running.
Would the xmin exported by that transaction prevent vacuum from removing
any tuples still needed for the flashback snapshot?

greetings, Florian Pflug