The term Convex Hull is used when the Analytical Engine simplifies the read request which has to be processed by the database(or a virtual provider). This in general means that a superset of the required data set is returned by the database which then has to be filtered by the Alalytical(OLAP) Engine. This might be necessary in case an SQL statement is extremely complex due to many local query restrictions or when local restrictions are not supported by the interface.
Simple Examples
- BWonHana
- Normally, the feature convex hull isn't applied in case the HANA Analytics-API is used . However, in very rare situations, the usage of the convex hull can reduce the data volume transferred from the database to the Analytic Engine. See note 2306646 and Example II.
- Virtual Providers based on HANA Models do not support local restrictions by default, see Example I for further details.
- BW on AnyDB
- When SQL is used, the feature convex hull can help to improve the query runtime by avoiding extremely complex(big) SQL statements. See Example III.
SAP Notes
- 2306646 Customer-specific convex hull for HDB/TREX queries (SAP_BW 7.50)
- 2145007 Customer-specific convex hull for HDB/TREX queries (SAP_BW 7.30, 7.31, 7.40)
- 2141172 Limit values for convex hull can be configured database-specifically
2723998 NCUM: Memory problem during execution of a non-cumulative key figure → new RSADMIN parameter NCUM_CONV_HULL_THRES
- 1814452 Large SID restriction on virtual BW InfoCube
Related Links
Virtual Cube based on Function: Query contains a characteristic with a large number of restrictions