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From aaron morton <aa...@thelastpickle.com>
Subject Re: CQL Reversed and Comparator reversed=true
Date Mon, 26 Mar 2012 17:14:16 GMT
> create column family Comments
>     with comparator = 'CompositeType(UTF8Type(reversed=True), UTF8Type)'
>     and key_validation_class = 'UTF8Type'
>     and default_validation_class = 'UTF8Type';
Looks ok. 

> SELECT FIRST 100 REVERSED 'z'..'0' from Comments where key = 'xyz';
try 
SELECT FIRST 100 REVERSED * from Comments where key = 'xyz';

Cheers


-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 24/03/2012, at 9:41 AM, Praveen Baratam wrote:

> Hello,
> 
> I am a bit confused about how to store and retrieve columns in Reversed order.
> 
> Currently I store comments for every blog post in a wide row per post.
> 
> I want to store and retrieve comments for each blog post in reversed/descending order
for efficiency as we display comments in descending order by time. Each comment gets a time
based sortable id which is stored as part of the first component of the composite type.
> 
> Below is the create statement for the column family that stores comments for posts.
> 
> create column family Comments
>     with comparator = 'CompositeType(UTF8Type(reversed=True), UTF8Type)'
>     and key_validation_class = 'UTF8Type'
>     and default_validation_class = 'UTF8Type';
> 
> and the CQL I use to retrieve is as follows
> 
> SELECT FIRST 100 REVERSED 'z'..'0' from Comments where key = 'xyz';
> 
> Am I doing the right thing?
> 
> Are the comments stored in descending time order in CF and with this CQL Query am I retrieving
the columns in their natural sort order with out any additional sorting overhead?
> 
> Thank you.


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