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From Aditya Narayan <ady...@gmail.com>
Subject Re: Calculating the size of rows in KBs
Date Thu, 10 Feb 2011 20:39:58 GMT
Thank you Aaron!!

But, If you are reading partial rows(that otherwise contain several
thousands of **valueless** columns) then do the column indexes help in
making the reads faster & more efficient than if they were not
valueless?
Perhaps, because they would only need to  look up whether the asked
column names exist in indexes for that row/key & they dont need to
deserialize the blocks in SST tables searching for column values. Am I
thinking right way??


-Aditya



On Fri, Feb 11, 2011 at 1:54 AM, Aaron Morton <aaron@thelastpickle.com> wrote:
> If you want to get the byte size of a particular row you will need to read it all back.
>
> If you connect with JConsole at look at you column families, there are attributes for
the max, min and mean row sizes.
>
> In general the entire row only exists in memory when it is contained in the first Memtable
it's written to. It may then be partially or fully read from disk during subsequent reads
or compactions.
>
> On disk format  described here may help http://wiki.apache.org/cassandra/ArchitectureSSTable
>
> Hope that helps
> Aaron
> On 10/02/2011, at 11:56 PM, Aditya Narayan <adynnn@gmail.com> wrote:
>
>> How can I get or calculate the size of  rows/ columns ? what are the
>> any overheads on memory for each column/row ?
>

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