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From John Laban <j...@pagerduty.com>
Subject Re: Composite keys and range queries
Date Wed, 14 Mar 2012 00:05:21 GMT
Forwarding to the Cassandra mailing list as well, in case this is more of
an issue on how I'm using Cassandra.

Am I correct to assume that I can use range queries on composite row keys,
even when using a RandomPartitioner, if I make sure that the first part of
the composite key is fixed?

Any help would be appreciated,
John



On Tue, Mar 13, 2012 at 12:15 PM, John Laban <john@pagerduty.com> wrote:

> Hi,
>
> I have a column family that uses a composite key:
>
> (ID, priority) -> ...
>
> Where the ID is a UUID and the priority is an integer.
>
> I'm trying to perform a range query now:  I want all the rows where the ID
> matches some fixed UUID, but within a range of priorities.  This is
> supported even if I'm using a RandomPartitioner, right?  (Because the first
> key in the composite key is the partition key, and the second part of the
> composite key is automatically ordered?)
>
> So I perform a range slices query:
>
> val rangeQuery = HFactory.createRangeSlicesQuery(keyspace, new CompositeSerializer, StringSerializer.get,
BytesArraySerializer.get)
>
> rangeQuery.setColumnFamily(RouteColumnFamilyName).
>             setKeys( new Composite(id, priorityStart), new Composite(id, priorityEnd)
).
>             setRange( null, null, false, Int.MaxValue )
>
>
> But I get this error:
>
> me.prettyprint.hector.api.exceptions.HInvalidRequestException: InvalidRequestException(why:start
key's md5 sorts after end key's md5.  this is not allowed; you probably should not specify
end key at all, under RandomPartitioner)
>
>
> Shouldn't they have the same md5, since they have the same partition key?
>
> Am I using the wrong query here, or does Hector not support composte range
> queries, or am I making some mistake in how I think Cassandra's composite
> keys work?
>
> Thanks,
> John
>
>

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