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From aaron morton <aa...@thelastpickle.com>
Subject Re: Generic questions over Cassandra 1.1/1.2
Date Mon, 26 Nov 2012 07:41:39 GMT
> Aaron first of all thanks for your precious help everytime ….
Thanks for using Cassandra since version 0.6 :)

> What it means that it will support "concurrent schema modifications?"
Previously we said you can change the schema online, but only do it at one node at a time.
In v1.2 you can have multiple clients issues schema changes without worrying about serialising
them. 


> I imagined that only CQL required a schema. What happen in a situation like this?
> 
> 1) I create a table using CQL
> 2) I add a new column using Thrift
> 3) I query for the column using CQL
For background see the "CQL for Cassandra Experts" and "CQL to Thrift migration" DS blog posts.


There are two types of CQL 3 tables, regular ones and those that use "COMPACT STORAGE". Regular
CQL 3 tables are not visible to Thrift as they store some extra data that thrift clients may
not understand. COMPACT STORAGE tables are visible to thrift for read and write, not sure
about schema mods. They do not support the compound primary key,

> Is there any noticeable performance difference between thrift or CQL3?
Off the top of my head it's within 5% (maybe 10%) under stress tests. See Eric's talk at the
Cassandra SF conference for the exact numbers.

Cheers

-----------------
Aaron Morton
Freelance Cassandra Developer
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 26/11/2012, at 11:58 AM, cbertu81@libero.it wrote:

> Aaron first of all thanks for your precious help everytime ....
> 
> 
> Some resources for CQL 3, it may match your needs. If not you can still use Thrift through
your favourite client...
> There have been a few articles on the DS blog http://www.datastax.com/dev/blog
> A talk at the conference by Eric  http://www.datastax.com/events/cassandrasummit2012/presentations
> I did a webinar about it last month http://www.datastax.com/resources/webinars/collegecredit
> 
> I will read all the links carefully. The idea was to keep Pelops (client I am familiar
with) and include CQL3 through the new Java driver Datastax is going to provide.
>> 
>> SELECT * FROM ctable WHERE basekey = ?  and myvalue = ? ORDER BY extensionkey 
>> DESC LIMIT 5
>> I haven't been able to do it ….
>> 
> That looks ok, what was the error ? 
> What cassandra version and what CQL version?
> 
> Cassandra 1.2 beta2 and CQL 3 -- honestly I didn't remember the exact  error (only that
it was about the order by) and I don't have Cassandra here to try. Will write more about this
tomorrow ... however if I avoided the where on secondary indexed column the query was ok.

> 
> 2) Is Cassandra still schemaless? One thing I loved is that to create a new 
>> column I didn't have to "alter" any cf before. 
>> Trying CQL 3 I noticed that if I try to make an insert of a new "column" not 
>> defined in schema I raised an exception. 
>> 
> CQL 3 requires a schema, however altering the schema is easier. And in 1.2 will support
concurrent schema modifications. 
> Thrift API is still schema less. 
> 
> What it means that it will support "concurrent schema modifications?" (if the answer
is in the link above I will know tomorrow :) )
> I imagined that only CQL required a schema. What happen in a situation like this?
> 
> 1) I create a table using CQL
> 2) I add a new column using Thrift
> 3) I query for the column using CQL
> 
> One more question:
> Is there any noticeable performance difference between thrift or CQL3?
> 
> Thanks,
> Carlo


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