Re: Three table database - period (?)

In article <958lej$31i$1_at_news.tue.nl>,   hidders_at_win.tue.nl (Jan Hidders) wrote:
> Vadim Tropashko wrote:
> >
> > Performance implications are probably much more severe than just
 more
> > joins. In traditional schema, for example, I could create composite
 key
> > index -- what do I do in metamodel?
>
> Nothing, you just define the one index on every attribute. :-) But
 that
> is "only" going to slow things down with a factor n where n is the
 number
> of attributes in the composite key.
>
Well, if I have FirstName and LastName attributes and asking for a ResultSet where FirstName='John' and LastName='Doe' in metamodel approach it could be that index on String attribute is not selective enough to filter either 'John' value, or 'Doe'. At the same time, optimizer might find that composite key FirstName+LastName is very selective in traditional schema. In first case, we do full table scan, therefore, query speed is proportional to the size of the table. In the second case, it's logariphm of the size of the table. Without being able to tune performance with indexes database simply won't scale.

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http://www.deja.com/ Received on Wed Jan 31 2001 - 19:19:30 CET