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while processing the key attribute. This increases the processing time of the key
attribute and the dimensions. If you have defined the natural relationships between
attributes, Analysis Services has an optimized code path that reduces the key at-
tribute processing, thereby reducing the overall dimension processing time. You
will see significant differences in processing times for large dimensions that have
hundreds of attributes. For some large dimensions (> 10 million members and >
100 attributes) you might reach the physical processing limits of a 32-bit environ-
ment and might have to move to 64-bit servers. Establishing relationships (as dis-
cussed) combined with other dimension optimizations (also discussed) can facilit-
ate processing for large dimensions on a 32-bit platform.
In the case of an unnatural hierarchy, only the key attribute has an attribute re-
lationship to all other attributes, so the relationship graph resembles
Figure 13-7
.
The system will only build indexes along attribute relationships, and build one-
to-many indexes for Country to Customer, State-Province to Customer, City to
Customer, and Zip Code to Customer. When you create a user hierarchy such
as Customer ZipCode City StateProvince Country, no additional indices get
created.
Unnatural hierarchies need to be materialized (identifying navigation
paths for members from one level to the next level and data correspond-
ing to members in a level need to be aggregated from the members at
the lowest level) during query time and will result in slow query perform-
ance. For example, to resolve a simple USA.Children query, the server
must use the Country Customer relationship to find all customers in
the USA; then use the Customer State Province relationship to find all
states for those customers in the USA. If there are millions of customers
in the USA, the query will traverse the millions of records, thereby res-
ulting in slow performance. In addition, if the server has cached values
or pre-calculated aggregations for "State-Province," the cache cannot be
used to resolve a country query because there are no direct relation-
ships between country and state province.
Figure 13-7
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