A Decision Support System (DSS) query on a very large table presents a special performance problem. If an ad-hoc query requires a table scan, every record in the table must be inspected, and this may take a long time. Where the query can be restricted to a single partition, or range of partitions, response time is dramatically reduced.
The performance of a DSS application can therefore be greatly improved by using a partition scan rather than a table scan.

(DSS) Decision support systems are defined as the class of warehouse system that deals with solving a semi-structured problem. This means the task has a structured component as well as an unstructured component. In short, the unstructured component involves human intuition and requires human interaction with the DSS. The well-structured components of a DSS are the decision rules stored as the problem-processing system. The intuitive, or creative, component is left to the user. The following represent some examples of semi-structured problems:

1. Choosing a spouse. While there are many structured rules (I want someone of my religion, who is shorter than me), there is still the unstructured, unquantifiable component to the process of choosing a spouse.
2. Choosing a site for a factory. This is a nonrecurring problem that has some structured components (cost of land, availability of workers, and so on), but there are many other unstructured components in this decision (i.e., quality of life).
3. Choosing a stock portfolio. Here the structured rules are the amount of risk and the performance of stocks, but the choice of stocks for a portfolio requires human intuition.

Decision support technology recognizes that many tasks require human intuition. For example, the process of choosing a stock portfolio is a task which has both structured and intuitive components. Certainly, rules are associated with choosing a stock portfolio, such as diversification of the stocks and choosing an acceptable level of risk. These factors can be easily quantified and stored in a database system, allowing the user of the system to create what-if scenarios. However, just because a system has well-structured components does not guarantee that the entire decision process is well-structured. One of the best ways to tell if a decision process is semi-structured is to ask the question:
Question: Do people with the same level of knowledge demonstrate different levels of skill?