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From Ed Anuff>
Subject Re: Second Cassandra users survey
Date Mon, 07 Nov 2011 16:25:53 GMT
This is basically what entity groups are about -

On Mon, Nov 7, 2011 at 5:26 AM, Peter Lin <> wrote:
> This feature interests me, so I thought I'd add some comments.
> Having used partition features in existing databases like DB2, Oracle
> and manual partitioning, one of the biggest challenges is keeping the
> partitions balanced. What I've seen with manual partitioning is that
> often the partitions get unbalanced. Usually the developers take a
> best guess and hope it ends up balanced.
> Some of the approaches I've used in the past were zip code, area code,
> state and some kind of hash.
> So my question related deterministic sharding is this, "what rebalance
> feature(s) would be useful or needed once the partitions get
> unbalanced?"
> Without a decent plan for rebalancing, it often ends up being a very
> painful problem to solve in production. Back when I worked mobile
> apps, we saw issues with how OpenWave WAP servers partitioned the
> accounts. The early versions randomly assigned a phone to a server
> when it is provisioned the first time. Once the phone was associated
> to that server, it was stuck on that server. If the load on that
> server was heavier than the others, the only choice was to "scale up"
> the hardware.
> My understanding of Cassandra's current sharding is consistent and
> random. Does the new feature sit some where in-between? Are you
> thinking of a pluggable API so that you can provide your own hash
> algorithm for cassandra to use?
> On Mon, Nov 7, 2011 at 7:54 AM, Daniel Doubleday
> <> wrote:
>> Allow for deterministic / manual sharding of rows.
>> Right now it seems that there is no way to force rows with different row keys will
be stored on the same nodes in the ring.
>> This is our number one reason why we get data inconsistencies when nodes fail.
>> Sometimes a logical transaction requires writing rows with different row keys. If
we could use something like this:
>> prefix.uniquekey and let the partitioner use only the prefix the probability that
only part of the transaction would be written could be reduced considerably.
>> On Nov 1, 2011, at 11:59 PM, Jonathan Ellis wrote:
>>> Hi all,
>>> Two years ago I asked for Cassandra use cases and feature requests.
>>> [1]  The results [2] have been extremely useful in setting and
>>> prioritizing goals for Cassandra development.  But with the release of
>>> 1.0 we've accomplished basically everything from our original wish
>>> list. [3]
>>> I'd love to hear from modern Cassandra users again, especially if
>>> you're usually a quiet lurker.  What does Cassandra do well?  What are
>>> your pain points?  What's your feature wish list?
>>> As before, if you're in stealth mode or don't want to say anything in
>>> public, feel free to reply to me privately and I will keep it off the
>>> record.
>>> [1]
>>> [2]
>>> [3]
>>> --
>>> Jonathan Ellis
>>> Project Chair, Apache Cassandra
>>> co-founder of DataStax, the source for professional Cassandra support

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