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From AJ ...@dude.podzone.net>
Subject Is this the proper use of OPP?
Date Mon, 13 Jun 2011 21:06:16 GMT
I'm just becoming aware of the restrictions of using an OPP as compared 
to Random.  Please let me know if I understand this correctly.

First off, if using the OPP only for an increased performance of range 
queries, then it will probably be very hard to predict if you will end 
up with hotspots or not and thus where and even how the data may be 
clustered together in a particular node.  This is because all the 
various keys of the various CFs may or may not have any correlation with 
one another.  So, in effect, you just have a big mess of keys of various 
ranges and formats, but they all are partitioned according to one global 
set of tokens that apply to ALL CFs of ALL keyspaces.

[main reason for post below...]
OTOH, if you want to use OPP to purposely cluster certain data together 
on specific nodes, such as for geographic partitioning, then you have to 
choose a prefix for all of the keys of ALL CFs and ALL keyspaces!  This 
is because they will all be partitioned based on the tokens assigned to 
the nodes.  IOW, if I had two datacenters, one in the US and another in 
Europe, then for all rows in all KSs and in all CFs, I would need to 
prepend a prefix to the keys, such as "US:" and "EU:".  The problem is I 
may not want ALL of my CFs to be partitioned this way; only specific 
ones.  Also, it may be very difficult if not impossible for all keys of 
all keyspaces and CFs to use keys of this form.  I'm not sure if Cass is 
designed for this.

However, if using the random partitioner, then there is no problem.  You 
can use any key of any type you want (UTF8, Long, etc.) since they are 
all hashed before deciding which node gets the key/row.

Do I understand things correctly or am I missing something?  Is Cass 
designed to use OPP this way or am I hacking it?  If so, is there an 
acceptable way to do geographic partitioning?

Also, what is OPP really good for?

Thanks!

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