about the last answer I still need some more clarifications, as I understand it if QUORUM is used, then reads doesn't get old values either? Or am I wrong?
Thank you very much!
Best regards, Daniel.
I'm not an expert, so take what I say with a grain of salt.
2010/4/21 Даниел Симеонов <email@example.com>:
> Hello,I think your question is paradoxical. If the use case really requires
> I am pretty new to Cassandra and I have some questions, they may seem
> trivial, but still I am pretty new to the subject. First is about the lack
> of a compareAndSet() operation, as I understood it is not supported
> currently in Cassandra, do you know of use cases which really require such
> operations and how these use cases currently workaround this .
the operation then there is no workaround by definition. The existence
of the workaround implies that the use case really did not require the
Anyhow, vector clocks are probably relevant to this question and your next one.
All of this is changing with vector clocks in Cassandra 0.7.
> Second topic I'd like to discuss a little bit more is about the read repair,
> as I understand is that it is being done by the timestamps supplied by the
> client application servers. Since computer clocks (which requires
> synchronization algorithms working regularly) diverge there should be a time
> frame during which the order of the client request written to the database
> is not guaranteed, do you have real world experiences with this? Is this
> similar to the casual consistency (
> http://en.wikipedia.org/wiki/Causal_consistency ) .What happens if two
> application servers try to update the same data and supply one and the same
> timestamp (it could happen although rarely), what if they try to update
> several columns in batch operation this way, is there a chance that the
> column value could be intermixed between the two update requests?
It would be required when your business rules do not allow any client
> I have one last question about the consistency level ALL, do you know of
> real use cases where it is required (instead of QUORUM) and why (both read
> and write)?
to read the old value. For example if it would be illegal to provide
an obsolete stock value.
> Thank you very much for your help to better understand 'Cassandra'!
> Best regards, Daniel.