[Tagdb] tags in separate table

[Nitin Borwankar]

Michal Migurski wrote:

>
> A question for Nitin:
> Do you actually implement schemas similar 
> to http://tagschema.com/blogs/tagschema/trinity-combined.jpg, or was 
> this just a thought exercise? Because it seems to me that such a 
> structure could be implemented virtually, using tables as 
> in http://tagschema.com/blogs/tagschema/trinity-triple.jpg with a gob 
> of indexes on the UserTagItem table.
>

Yes, you could make do just with the facts (UserItemTag) table. But if 
you also have the other tables then some of the queries that involve 
only two tables could be offloaded to the corresponding association 
table and it's index.
Otherwise you have everything - reads and writes - hitting the fact table.
With the extra tables you do have extra inserts - you have to insert in 
the association table(s) and the fact table, but the expectation is that 
you get something back.  You spread the load across the whole tagschema.

Having said that I don't have numbers at which this overhead becomes 
justifiable.
A lot will also depend on the sizes of the item, tag, user tables and 
their indexes.

Nitin Borwankar

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>
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