Re: Use for CREATE DIMENSION in O10g?

Aha, thanks. So would this be a fair summary: by suggesting to the CBO where a more-granular materialized view can be rolled up into larger grains, it saves storage space at the possible expense of some processing speed? (Since the granular materialized view's data will need to be summed in real time to, for instance, present quarterly subtotals instead of monthly.

Appreciate you sticking with this.

> John,
>
> I think there may be a misunderstanding about what a materialized view can
> do for you.
>
> If I have a query that gets the total sales by product by region by month,
> then I can create a materialized view which stores the result of that
query.
> The next time I do the same query, the CBO will consider using those
results
> from the materialized view instead of doing the same work over again.
> (There are a few points about data currency and query rewriting which I
will
> gloss over at this stage). Now if I query total sales by product by
region
> by quarter, the CBO will not consider the materialized view even though I
> know that months can be rolled up into quarters. There is where a
dimension
> comes in - a dimension tells the CBO that months be rolled up into
quarters.
> Now the CBO can consider using the materialized view by summarizing the
> months into quarters.
>
> In your approach, there would be two or more materialized views to be
> queried upon. This means extra storage is needed for the extra
matrialized
> views.
>
>
Received on Thu Mar 25 2004 - 22:52:38 CST