Re: New feature request: FlashBack Query

"Jonah H. Harris" <jonah(dot)harris(at)gmail(dot)com> writes:

> On 2/17/07, Joshua D. Drake <jd(at)commandprompt(dot)com> wrote:
>> My understanding is that the main difference is that rollbacks are
>> inexpensive for us, but expensive for Oracle.
>
> Yes, Oracle is optimized for COMMIT, we're optimized for ROLLBACK :)

I used to say that too but I've since realized it's not really true. It's more
like Oracle is optimized for data that's committed long in the past and we're
optimized for data that's been recently updated.

In Oracle the data that's been committed long in the past requires no
transactional overhead but the data that's been recently updated requires lots
of work to fetch the right version.

In Postgres it's the other way around. data that's been committed deleted long
ago requires extra work to clean up but data that's been recently changed
requires little additional work to see the correct version.

In a sense then it's the opposite of what we usually say. Oracle is optimized
for mostly static data. Postgres is optimized for changing data.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com