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From Praveen Baratam <praveen.bara...@gmail.com>
Subject Re: CQL Reversed and Comparator reversed=true
Date Mon, 26 Mar 2012 19:05:34 GMT
Thank you Aaron!

On Mon, Mar 26, 2012 at 10:44 PM, aaron morton <aaron@thelastpickle.com>wrote:

> 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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