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From aaron morton <aa...@thelastpickle.com>
Subject Re: Timeseries data
Date Sun, 31 Mar 2013 10:12:47 GMT
> I think if you use Level compaction, the number of sstables you will touch will be less
because sstables in each level is non overlapping except L0.
You will want to do some testing because LCS uses extra IO to make those guarantees. You will
also want to look at the SSTable size with LCS if you are going to have wide rows. 

Cheers

-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 29/03/2013, at 12:18 PM, sankalp kohli <kohlisankalp@gmail.com> wrote:

> I think if you use Level compaction, the number of sstables you will touch will be less
because sstables in each level is non overlapping except L0.
> 
> 
> On Wed, Mar 27, 2013 at 8:20 PM, aaron morton <aaron@thelastpickle.com> wrote:
> sstablekey can help you find which sstables your keys are in. 
> 
> But yes, a slice call will need to read from all sstables the row has a fragment in.
This is one reason we normally suggest partitioning time series data by month or year or something
sensible in your problem domain. 
> 
> You will probably also want to use reversed comparators so you do not have to use reversed
in your query. 
> 
> Hope that helps. 
> 
> -----------------
> Aaron Morton
> Freelance Cassandra Consultant
> New Zealand
> 
> @aaronmorton
> http://www.thelastpickle.com
> 
> On 28/03/2013, at 8:25 AM, Bryan Talbot <btalbot@aeriagames.com> wrote:
> 
>> In the worst case, that is possible, but compaction strategies try to minimize the
number of SSTables that a row appears in so a row being in ALL SStables is not likely for
most cases.
>> 
>> -Bryan
>> 
>> 
>> 
>> On Wed, Mar 27, 2013 at 12:17 PM, Kanwar Sangha <kanwar@mavenir.com> wrote:
>> Hi – I have a query on Read with Cassandra. We are planning to have dynamic column
family and each column would be on based a timeseries.
>> 
>>  
>> 
>> Inserting data — key => ‘xxxxxxx′, {column_name => TimeUUID(now), :column_value
=> ‘value’ }, {column_name => TimeUUID(now), :column_value => ‘value’ },…………..
>> 
>>  
>> 
>> Now this key might be spread across multiple SSTables over a period of days. When
we do a READ query to fetch say a slice of data from this row based on time X->Y , would
it need to get data from ALL sstables ?
>> 
>>  
>> 
>> Thanks,
>> 
>> Kanwar
>> 
>>  
>> 
>> 
> 
> 


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