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From Robert Jackson <robe...@promedicalinc.com>
Subject Re: "range query" vs "slice range query"
Date Wed, 25 May 2011 14:11:40 GMT
Also, it is my understanding that if you are not using OrderPreservingPartitioner a get_range_slices
may not return what you would expect. 


With the RandomPartitioner you can iterate over the complete list by using the last row key
as the start for subsequent requests, but if you are using a single query you will be returned
all the rows where the returned row key's md5 is between the md5 of the start row key and
stop row key. 


Reference: 
http://wiki.apache.org/cassandra/FAQ - " Why aren't range slices/sequential scans giving me
the expected results?" 

Robert Jackson 

----- Original Message -----

From: "Jonathan Ellis" <jbellis@gmail.com> 
To: user@cassandra.apache.org 
Sent: Wednesday, May 25, 2011 8:54:34 AM 
Subject: Re: "range query" vs "slice range query" 

get_range_slices is the api to get a slice (of columns) from each of a 
range (of rows) 

On Wed, May 25, 2011 at 3:42 AM, david lee <iecanfly@gmail.com> wrote: 
> hi guys, 
> i'm reading up on the book "Cassandra - Definitive guide" 
> and i don't seem to understand what it says about "ranges and slices" 
> my understanding is 
> a range as in "a mathematical range to define a subset from an ordered set 
> of elements", 
> in cassandra typically means a range of rows whereas 
> a slice means a range of columns. 
> a range query refers to a query to retrieve a range of rows whereas 
> a slice range queyr refers to a query to retrieve range of columns within a 
> row. 
> i may be talking about total nonsense but i really am more confused after 
> reading this portion of the book 
> http://books.google.com/books?id=MKGSbCbEdg0C&pg=PA134&lpg=PA134&dq=cassandra+%22range+query%22+%22range+slice%22&source=bl&ots=XoPB4uA60u&sig=uDDoQe0FRkQobHnr-vPvvQ3B8TQ&hl=en&ei=ub3cTcvGLZLevQOuxs3CDw&sa=X&oi=book_result&ct=result&resnum=4&ved=0CCwQ6AEwAw#v=onepage&q=cassandra%20%22range%20query%22%20%22range%20slice%22&f=false

> many thanx in advance 
> david 
> 



-- 
Jonathan Ellis 
Project Chair, Apache Cassandra 
co-founder of DataStax, the source for professional Cassandra support 
http://www.datastax.com 


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