Re: Atomic file data replace API

[Thomas Bellman <bellman@nsc.liu.se>]

Olaf van der Spek wrote:

> On Sat, Jan 8, 2011 at 10:43 PM, Thomas Bellman <bellman@nsc.liu.se> wrote:
>> So, basically database transactions with an isolation level of
>> "committed read", for file operations.  That's something I have
>> wanted for a long time, especially if I also get a rollback()
>> operation, but have never heard of any Unix that implemented it.
> 
> True, that's why this feature request is here.
> Note that it's (ATM) only about  single file data replace.

That particular problem was solved with the introduction of the
rename(2) system call in 4.2BSD a bit more than a quarter of a
century ago.  There is no need to introduce another, less flexible,
API for doing the same thing.

>> A separate commit() operation would be better than conflating it
>> with close().  And as I said, we want a rollback() as well.  And
>> a process that terminates without committing the transaction that
>> it is performing, should have the transaction automatically rolled
>> back.
> 
> What could you do between commit and close?

More write() operations, of course.  Just like you can continue
with more transactions after a COMMIT WORK call without having
to close and re-open the database in SQL.


	/Bellman