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From Corey Nolet <cjno...@gmail.com>
Subject Re: Tracking cardinality in Accumulo
Date Fri, 16 May 2014 22:04:06 GMT
What's the expected size of your unique key set? Thousands? Millions?
Billions?

You could probably use a table structure similar to
https://github.com/calrissian/accumulo-recipes/tree/master/store/metrics-storebut
just have it emit 1's instead of summing them.

I'm thinking maybe your mappings could be like this:
group=anything, type=NAME, name=John(etc...)

perhaps a ColumnQualifierGrouping iterator could be applied at scan time to
add up the cardinalities for the quals over the given time range being
scanned where cardinalities across different time units get aggregated
client side.




On Fri, May 16, 2014 at 5:19 PM, David Medinets <david.medinets@gmail.com>wrote:

> Yes, the data has not yet been ingested. I can control the table
> structure; hopefully by integrating (or extending) the D4M schema.
>
> I'm leaning towards using https://github.com/addthis/stream-lib as part
> of the ingest process. Upon start up, existing tables would be analyzed to
> find cardinality. Then as records are ingested, the cardinality would be
> adjusted as needed. I don't yet know how to store the cardinality
> information so that restarting the ingest process doesn't require
> re-processing all the data. Still researching.
>
>
> On Fri, May 16, 2014 at 4:19 PM, Corey Nolet <cjnolet@gmail.com> wrote:
>
>> Can we assume this data has not yet been ingested? Do you have control
>> over the way in which you structure your table?
>>
>>
>>
>> On Fri, May 16, 2014 at 1:54 PM, David Medinets <david.medinets@gmail.com
>> > wrote:
>>
>>> If I have the following simple set of data:
>>>
>>> NAME John
>>> NAME Jake
>>> NAME John
>>> NAME Mary
>>>
>>> I want to end up with the following:
>>>
>>> NAME 3
>>>
>>> I'm thinking that perhaps a HyperLogLog approach should work. See
>>> http://en.wikipedia.org/wiki/HyperLogLog for more information.
>>>
>>> Has anyone done this before in Accumulo?
>>>
>>
>>
>

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