Thanks. I found that article later. I was definitely off-base with
respect to OPP. Random partitioning is pretty much the way to go and
datastax has a good article on geographic distribution:
http://www.datastax.com/docs/0.8/operations/datacenter
Sorry for the long pointless post previously. But, FWIW, I don't see
much use for OPP other than the corner case of a cluster consisting on 1
ks and 1 cf, such as an index. I will have to read Dominic's post on
having multiple Cass clusters running on the same nodes.
On 6/14/2011 4:46 AM, Eric tamme wrote:
I would point you to this article, it does a good job describing OPP
and pretty much answers the specific questions you asked.
http://ria101.wordpress.com/2010/02/22/cassandra-randompartitioner-vs-orderpreservingpartitioner/
-Eric
On Mon, Jun 13, 2011 at 5:06 PM, AJ<a...@dude.podzone.net> wrote:
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!
