Invoking Context Analysis for a Star Schema With a Fan Trap

When a star schema contains a segment with aggregated facts and a lower-level segment with the related detail-level facts, a request that performs aggregation on both levels and returns them sorted by the higher level can experience the multiplicative effect. This means that the fact values that are already aggregated may be re-aggregated and, therefore, return multiplied values.

When the adapter detects the multiplicative effect, it turns optimization off in order to handle the request processing and circumvent the multiplicative effect. However, performance is degraded when a request is not optimized.

A new context analysis process has been introduced in this release that detects the multiplicative effect and generates SQL script commands that retrieve the correct values for each segment context. These scripts are then passed to the RDBMS as subqueries in an optimized SQL statement.

To activate the context analysis feature, click Change Common Adapter Settings on the Adapters page of the Web Console. Then select Yes for the FCA parameter in the Miscellaneous Settings section and click Save, as shown in the following image.