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From Aaron Morton <aa...@thelastpickle.com>
Subject Re: Cassandra token range support for Hadoop (ColumnFamilyInputFormat)
Date Tue, 20 May 2014 06:58:27 GMT
>> “between 1.2.6 and 2.0.6 the setInputRange(startToken, endToken) is not working”
> Can you confirm or disprove?


My reading of the code is that it will consider the part of a token range (from vnodes or
initial tokens) that overlap with the provided token range. 

> I’ve already got one confirmation that in C* version I use (1.2.15) setting limits
with setInputRange(startToken, endToken) doesn’t work.
Can you be more specific ?

> work only for ordered partitioners (in 1.2.15).

it will work with ordered and unordered partitioners equally. The difference is probably what
you consider to “working” to mean.  The token ranges are handled the same, it’s the
row in them that changes. 

Cheers
Aaron

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

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

On 20/05/2014, at 11:37 am, Anton Brazhnyk <anton.brazhnyk@genesys.com> wrote:

> Hi Aaron,
>  
> I’ve seen the code which you describe (working with splits and intersections) but that
range is derived from keys and work only for ordered partitioners (in 1.2.15).
> I’ve already got one confirmation that in C* version I use (1.2.15) setting limits
with setInputRange(startToken, endToken) doesn’t work.
> “between 1.2.6 and 2.0.6 the setInputRange(startToken, endToken) is not working”
> Can you confirm or disprove?
>  
> WBR,
> Anton
>  
> From: Aaron Morton [mailto:aaron@thelastpickle.com] 
> Sent: Monday, May 19, 2014 1:58 AM
> To: Cassandra User
> Subject: Re: Cassandra token range support for Hadoop (ColumnFamilyInputFormat)
>  
> The limit is just ignored and the entire column family is scanned.
> Which limit ? 
> 
> 
> 1. Am I right that there is no way to get some data limited by token range with ColumnFamilyInputFormat?
> From what I understand setting the input range is used when calculating the splits. The
token ranges in the cluster are iterated and if they intersect with the supplied range the
overlapping range is used to calculate the split. Rather than the full token range. 
>  
> 2. Is there other way to limit the amount of data read from Cassandra with Spark and
ColumnFamilyInputFormat,
> so that this amount is predictable (like 5% of entire dataset)?
> if you suppled a token range is that is 5% of the possible range of values for the token
that should be close to a random 5% sample. 
>  
>  
> Hope that helps. 
> Aaron
>  
> -----------------
> Aaron Morton
> New Zealand
> @aaronmorton
>  
> Co-Founder & Principal Consultant
> Apache Cassandra Consulting
> http://www.thelastpickle.com
>  
> On 14/05/2014, at 10:46 am, Anton Brazhnyk <anton.brazhnyk@genesys.com> wrote:
> 
> 
> Greetings,
> 
> I'm reading data from C* with Spark (via ColumnFamilyInputFormat) and I'd like to read
just part of it - something like Spark's sample() function.
> Cassandra's API seems allow to do it with its ConfigHelper.setInputRange(jobConfiguration,
startToken, endToken) method, but it doesn't work.
> The limit is just ignored and the entire column family is scanned. It seems this kind
of feature is just not supported 
> and sources of AbstractColumnFamilyInputFormat.getSplits confirm that (IMO).
> Questions:
> 1. Am I right that there is no way to get some data limited by token range with ColumnFamilyInputFormat?
> 2. Is there other way to limit the amount of data read from Cassandra with Spark and
ColumnFamilyInputFormat,
> so that this amount is predictable (like 5% of entire dataset)?
> 
> 
> WBR,
> Anton
> 


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