MapViewer WMS GetMap uses SDO_FILTER

Question

When I use the WMS request GetMap, MapViewer uses SDO_FILTER for the generated queries. This is not always accurate because sometimes features are not selected and drawn. How can I make MapViewer use SDO_RELATE instead of SDO_FILTER?

Answer 1

The fact that mapping applications use sdo_filter is because it is much more faster to supply a resultset which normally is bigger than the actual set needed for a rectangular view in such an application, then to use an operator like sdo_relate to get an exact matching resultset.
After all speed is important in (web)mapping applications.
This is also noted in the user manual:
http://download.oracle.com/docs/html/B14255_01/sdo_intro.htm#sthref91
Extract:
Spatial uses a spatial index to implement the primary filter. Spatial does not require the use of both the primary and secondary filters. In some cases, just using the primary filter is sufficient. For example, a zoom feature in a mapping application queries for data that has any interaction with a rectangle representing visible boundaries. The primary filter very quickly returns a superset of the query. The mapping application can then apply clipping routines to display the target area.
The purpose of the primary filter is to quickly create a subset of the data and reduce the processing burden on the secondary filter. The primary filter, therefore, should be as efficient (that is, selective yet fast) as possible. This is determined by the characteristics of the spatial index on the data.
However, I think, it should not return less features then the sdo_relate.
Maybe a Mapviewer expert can help you further.
Luc