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From Peter Hsu <>
Subject Re: Human readable Cassandra limitations
Date Mon, 10 May 2010 20:23:35 GMT
Thanks for the response, Paul.

Very helpful, but very general at the same time.  I'm still having trouble translating these
into actual use cases.    Let me think of some better questions before I continue the thread,
but I'd like to address one of the weaknesses you brought up:

> * Cassandra and its siblings are weak at ad hoc queries on tables
> that you did not think to index in advance

What is the normal way of dealing with this in Cassandra?  Would you just create a new "index"
and bring a big honking machine to the table to process all the existing data in the database
and store the new "index"?

On May 10, 2010, at 11:22 AM, Paul Prescod wrote:

> This is a very, very big topic. For the most part, the issues are
> covered in the various SQL versus NoSQL debates all over the Internet.
> For example:
> * Cassandra and its NoSQL siblings have no concept of an in-database "join"
> * Cassandra and its NoSQL siblings do not allow you to update
> multiple "tables" in a single transactions
> * Cassandra's API is specific to it, and not portable to any other data store
> * Cassandra currently has simplistic facilities to deal with various
> kinds of conflicting write.
> * Cassandra is strongly optimized for multiple machine distributions,
> whereas relational databases tend to be optimized for a single
> powerful machine.
> * Cassandra and its siblings are weak at ad hoc queries on tables
> that you did not think to index in advance
> On Mon, May 10, 2010 at 11:06 AM, Peter Hsu <> wrote:
>> I've seen a lot of threads and posts about why Cassandra is great.  I'm fairly sold
on the features, and the few big deployments on Cassandra give it a lot of credibility.
>> However, I don't believe in magic bullets, so I really want to understand the potential
downsides of Cassandra.  Right now, I don't really have a clue as to what Cassandra is bad
at.  I took a look at which is helpful,
but doesn't characterize its weaknesses in ways that I can really comprehend until I've actually
used Cassandra and understand some of the internals.  It seems that the community would benefit
from being able to answer some of these questions in terms of real world use cases.
>> My main questions:
>>  * Are there designs in which a SQL database out-performs or out-scales Cassandra?
>>  * Is there a pros vs cons page of Cassandra against an open source SQL database
(MySQL or Postgres)?
>> I do plan on attending the training session next Friday in Palo Alto, but it'd be
great if I had some more food for thought before I attend.

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