> But this becomes troublesome if I add or remove nodes. What effectively I > want is to partition on the unique id of the record modulus N (id % N; where > N is the number of nodes). This is exactly the problem consistent hashing (used by cassandra) is designed to solve. If you hash the key and modulo the number of nodes, adding and removing nodes requires a lot of data to move.
> I want to be able to randomly distribute a large set of records but keep them > clustered in one wide row per node. Sounds like you should revisit your data modelling, this is a pretty well known anti pattern. When rows get above a few 10’s of MB things can slow down, when they get above 50 MB they can be a pain, when they get above 100MB it’s a warning sign. And when they get above 1GB, well you you don’t want to know what happens then. It’s a bad idea and you should take another look at the data model. If you have to do it, you can try the ByteOrderedPartitioner which uses the row key as a token, given you total control of the row placement. Cheers ----------------- Aaron Morton New Zealand @aaronmorton Co-Founder & Principal Consultant Apache Cassandra Consulting http://www.thelastpickle.com On 4/12/2013, at 8:32 pm, Vivek Mishra <mishra.v...@gmail.com> wrote: > So Basically you want to create a cluster of multiple unique keys, but data > which belongs to one unique should be colocated. correct? > > -Vivek > > > On Tue, Dec 3, 2013 at 10:39 AM, onlinespending <onlinespend...@gmail.com> > wrote: > Subject says it all. I want to be able to randomly distribute a large set of > records but keep them clustered in one wide row per node. > > As an example, lets say I’ve got a collection of about 1 million records each > with a unique id. If I just go ahead and set the primary key (and therefore > the partition key) as the unique id, I’ll get very good random distribution > across my server cluster. However, each record will be its own row. I’d like > to have each record belong to one large wide row (per server node) so I can > have them sorted or clustered on some other column. > > If I say have 5 nodes in my cluster, I could randomly assign a value of 1 - 5 > at the time of creation and have the partition key set to this value. But > this becomes troublesome if I add or remove nodes. What effectively I want is > to partition on the unique id of the record modulus N (id % N; where N is the > number of nodes). > > I have to imagine there’s a mechanism in Cassandra to simply randomize the > partitioning without even using a key (and then clustering on some column). > > Thanks for any help. >
