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From David McNelis <>
Subject Re: Storing pre-sorted data
Date Wed, 12 Oct 2011 16:39:42 GMT
Is it an option to not convert the data to binary prior to inserting into
Cassandra?  Also, how large are the strings you're sorting?  If its viable
to not convert to binary before writing to Cassandra, and you use one of the
string based column ordering techniques (utf8, ascii, for example), then the
data would be sorted without you  needing to specifically worry about that.
 Of course, if the strings are lengthy you could run into  additional

On Wed, Oct 12, 2011 at 11:34 AM, Matthias Pfau <> wrote:

> Hi there,
> we are currently building a prototype based on cassandra and came into
> problems on implementing sorted lists containing millions of items.
> The special thing about the items of our lists is, that cassandra is not
> able to sort them as the data is stored in a binary format which is not
> sortable. However, we are able to sort the data before the plain data gets
> encoded (our application is responsible for the order).
> First Approach: Storing Lists in ColumnFamilies
> ***
> We first tried to map the list to a single row of a ColumnFamily in a way
> that the index of the list is mapped to the column names and the items of
> the list to the column values. The column names are increasing numbers which
> define the sort order.
> This has the major drawback that big parts of the list have to be rewritten
> on inserts (because the column names are numbered by their index), which are
> quite common.
> Second Approach: Storing the whole List as Binary Data:
> ***
> We tried to store the compressed list in a single column. However, this is
> only feasible for smaller lists. Our lists are far to big leading to multi
> megabyte reads and writes. As we need to read and update the lists quite
> often, this would put our Cassandra cluster under a lot of pressure.
> Ideal Solution: Native support for storing lists
> ***
> We would be very happy with a way to store a list of sorted values without
> making improper use of column names for the list index. This implies that we
> would need a possibility to insert values at defined positions. We know that
> this could lead to problems with concurrent inserts in a distributed
> environment, but this is handled by our application logic.
> What are your ideas on that?
> Thanks
> Matthias

*David McNelis*
Lead Software Engineer
Agentis Energy
c: 219.384.5143

*A Smart Grid technology company focused on helping consumers of energy
control an often under-managed resource.*

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