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From Jeff Zhang <zjf...@gmail.com>
Subject Re: Design Pattern - Tag Cloud / Inverted Index
Date Sun, 27 Dec 2009 09:25:48 GMT
I think this is a typical paradigm that's suit for many-to-many relationship


Jeff Zhang



On Sun, Dec 27, 2009 at 12:52 AM, August Zajonc <augustz@augustz.com> wrote:

> Just getting up to speed with Cassandra and the terminology and
> concepts. Lots of fun. Apologies for a beginner question.
>
> Focusing on how the data will be used is very helpful in coming up
> with a model.
>
> I have a question about a design pattern I expect is relatively
> common. It's the tag pattern (or sets or inverted index...)
>
> Item A
> - Tag A
> - Tag B
> - Tag C
>
> Tag A
> - Item A
> - Item B
> - Item C
>
> I want fast access using the item as a key and fast access when using
> the tag as a key (inverted index). This let's met answer the
> questions, what tags have been applied to this item, and what items
> belong to this tag, both very quickly.
>
> Looking at the data model a simple solution is two column families,
> one containing items as the row-key with tags as columns, and a second
> with tags as the row-key with items as columns. This gives me fast
> access at the cost of 2x the writes (cheap) and storage (also cheap).
> So not bad.
>
> Curious what the standard pattern is here.
>
> One other issue is consistency. Since my writes are idempotent
> consistency could be maintained with a writelog or similar replayed on
> recovery. It feels like this will have been done enough someone will
> have some good pointers.
>
> Many cheers,
>
> - August
>

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