Re: New feature request: FlashBack Query

Chad Wagner wrote:
> On 2/17/07, elein <elein(at)varlena(dot)com> wrote:
>>
>> For other recent time travel ideas see:
>> http://www.varlena.com/GeneralBits/122.php
>> Time travel is not cheap, though.
>>
>
>
> I am sure this topic has probably been beaten to death in the past, but has
> anyone talked about the advantages of Oracle's MVCC model versus
> PostgreSQL's MVCC model? Oracle achieves multiversioning by using
> rollback/undo segments, where PostgreSQL appears to place (essentially) the
> undo in the same space as the table.

My understanding is that the main difference is that rollbacks are
inexpensive for us, but expensive for Oracle. Talk to an Oracle DBA
about their Rollback logs :0.

However, they don't have vacuum, we do.

Joshua D. Drake

>
> If I were to guess this is probably a major thing to change. Clearly there
> are advantages to both, with Oracle essentially the space consumed by a
> modified row is immediately available for reuse and generally there is
> little row migration assuming there is enough space on the block so you
> should be able to avoid updates to the index and the bloating that seems to
> go along with vacuuming.
>
> Is there any previous discussions that folks could point out here?
>

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