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From Ted Dunning <tdunn...@maprtech.com>
Subject Re: [DISCUSSION] Accumulo, another BigTable clone, has shown up on Apache Incubator as a proposal
Date Tue, 06 Sep 2011 16:31:45 GMT
Hbase offers co-processors which should be able to do this.

And median *can* be accumulated in a small amount of memory.  It is a little
trickier than mean, but still doable.

On Tue, Sep 6, 2011 at 11:21 AM, Duane Moore <duane.moore@issinc.com> wrote:

> - Aggregation
> Accumulo offers the ability to specify an aggregator for an individual
> column family or column. This allows you to keep a row count, or summation
> of numerical values that may be stored in a particular column. It would
> appear the function has to operate on the subset of values stored for that
> column in the table at a particular time since it keeps the aggregate
> value in memory. So this may not be able to handle certain aggregation
> functions like 'median' for instance. But functions like sum, max, min,
> mean, and count should all be supportable.
> I could not find a comparable feature within HBase, but HBase does offer
> an atomic function called incremementColumnValue on the HTable class which
> appears can be leveraged to provide aggregation behavior.
>

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