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From Sean Owen <>
Subject Re: Why do userid & itemid have to be long?
Date Wed, 01 Jun 2011 07:40:33 GMT
It is for performance -- it used to allow any Comparable type but the object
overhead slowed things down by 2-3x.
It looks like you are using integer values already in Mongo, am I reading
that right? those look like 12-byte hex values. Is it a question of
reading/writing them as such then rather than treating as strings in Mongo?
If you really have to convert such a thing to/from String, I bet that
writing your own simple encoder/decoder runs much faster.

On Wed, Jun 1, 2011 at 3:50 AM, Mike Khristo <> wrote:

> Rather, how can I use string-based userid/itemid's without having the deal
> with the slowness associated with mapping them to a long?
> In the MongoDataModel, for example, significant time/overhead goes into
> converting the unique id's to long...  I'm still getting my head wrapped
> around mahout, but this seems like a significant limitation. I have to
> assume there's some logic behind the decision to restrict them to long, but
> i didn't find anything about it in Mahout in Action or the list.
> Thanks.

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