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From Aaron Morton <aa...@thelastpickle.com>
Subject Re: CQL 3 and wide rows
Date Tue, 20 May 2014 07:06:14 GMT
In a CQL 3 table the only **column** names are the ones defined in the table, in the example
below there are three column names. 


>> CREATE TABLE keyspace.widerow (
>> row_key text,
>> wide_row_column text,
>> data_column text,
>> PRIMARY KEY (row_key, wide_row_column));
>> 
>> Check out, for example, http://www.datastax.com/dev/blog/schema-in-cassandra-1-1.​

Internally there may be more **cells** ( as we now call the internal columns). In the example
above each value for row_key will create a single partition (as we now call internal storage
engine rows). In each of those partitions there will be cells for each CQL 3 row that has
the same row_key, those cells will use a Composite for the name. The first part of the composite
will be the value of the wide_row_column and the second will be the literal name of the non
primary key columns. 

IMHO Wide partitions (storage engine rows) are more prevalent in CQL3 than thrift models.


> But still - I do not see Iteration, so it looks to me that CQL 3 is limited when compared
to CLI/Hector.
Now days you can do pretty much everything you can in cli. Provide an example and we may be
able to help. 

Cheers
Aaron

-----------------
Aaron Morton
New Zealand
@aaronmorton

Co-Founder & Principal Consultant
Apache Cassandra Consulting
http://www.thelastpickle.com

On 20/05/2014, at 8:18 am, Maciej Miklas <mac.miklas@gmail.com> wrote:

> Hi James,
> 
> Clustering is based on rows. I think that you meant not clustering columns, but compound
columns. Still all columns belong to single table and are stored within single folder on one
computer. And it looks to me (but I’am not sure) that CQL 3 driver loads all column names
into memory - which is confusing to me. From one side we have wide row, but we load whole
into ram…..
> 
> My understanding of wide row is a row that supports millions of columns, or similar things
like map or set. In CLI you would generate column names (or use compound columns) to simulate
set or map,  in CQL 3 you would use some static names plus Map or Set structures, or you could
still alter table and have large number of columns. But still - I do not see Iteration, so
it looks to me that CQL 3 is limited when compared to CLI/Hector.
> 
> 
> Regards,
> Maciej
> 
> On 19 May 2014, at 17:30, James Campbell <james@breachintelligence.com> wrote:
> 
>> Maciej,
>> 
>> In CQL3 "wide rows" are expected to be created using clustering columns.  So while
the schema will have a relatively smaller number of named columns, the effect is a wide row.
 For example:
>> 
>> CREATE TABLE keyspace.widerow (
>> row_key text,
>> wide_row_column text,
>> data_column text,
>> PRIMARY KEY (row_key, wide_row_column));
>> 
>> Check out, for example, http://www.datastax.com/dev/blog/schema-in-cassandra-1-1.​
>> 
>> James
>> From: Maciej Miklas <mac.miklas@gmail.com>
>> Sent: Monday, May 19, 2014 11:20 AM
>> To: user@cassandra.apache.org
>> Subject: CQL 3 and wide rows
>>  
>> Hi *,
>> 
>> I’ve checked DataStax driver code for CQL 3, and it looks like the column names
for particular table are fully loaded into memory, it this true?
>> 
>> Cassandra should support wide rows, meaning tables with millions of columns. Knowing
that, I would expect kind of iterator for column names. Am I missing something here? 
>> 
>> 
>> Regards,
>> Maciej Miklas
> 


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