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From Roshni Rajagopal <>
Subject Re: Does Cassandra support operations in a transaction?
Date Thu, 02 Aug 2012 04:24:47 GMT
Hi Ivan,

Cassandra supports 'tunable consistency' . If you always read and write at a quorum (or local
quorum for multi data center) from one , you can guarantee that the results will be consistent
as in all the data will be compared and the latest will be returned, and no data will be out
of date. This is at a loss of performance- it will be fastest to just read and write once
rather than check a quorum of nodes.

What you chose depends on what your application needs are. Is it ok if some users receive
out of date data (it isn't earth shattering if someone doesn't know what you're eating right
now), or is it a banking transaction system where all entities must be consistently updated.

So designing in cassandra priortizes de-normalization. You cannot have referential integrity
that 2 tables (col families in cassandra) are in sync because the database has designed it
to be so using foreign keys. The application needs to ensure that all data in column families
are accurate and not out of sync, because data elements may be duplicated in different col

You cannot have 2 different entities and ensure that changes to both will be done and then
only be visible to others.


From: Jeffrey Kesselman <<>>
Reply-To: "<>" <<>>
To: "<>" <<>>
Subject: Re: Does Cassandra support operations in a transaction?

Short story is that few if any of the NoSql systems supprot transactions natively. Thats oen
of the big compromises they make.  What they call "eventual consistancy" is actually eventual
Durabiltiy in ACID terms.

Consistancy, as meant by the C in ACID,  is not gauranteed at all.

On Wed, Aug 1, 2012 at 6:21 AM, Ivan Jiang <<>>
    I am a new guy to Cassandra, I wonder if available to call Cassandra in one Transaction
such as in Relation-DB.

Thanks in advance.

Best Regards,
Ivan Jiang

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