Shape selection performance for large shapefile is good only while using spatial indices. Selection speed at full scale is very slow even with them, because of the usage of slow Extents COM class.
The changes are needed to make selection fast in spite of the presence of spatial index and scale. The support of new Shapefile.FastMode property is needed as well.
Comments: Reviewing this before v4.9.3 beta release: it seems some optimizations were made, it uses cached extents for each shape (taking into account fast mode), doesn't use COM Extents objects, uses disk-based or in-memory spatial index depending on availability. I don't see much else that can be done. Therefore closed.
The changes are needed to make selection fast in spite of the presence of spatial index and scale. The support of new Shapefile.FastMode property is needed as well.
Comments: Reviewing this before v4.9.3 beta release: it seems some optimizations were made, it uses cached extents for each shape (taking into account fast mode), doesn't use COM Extents objects, uses disk-based or in-memory spatial index depending on availability. I don't see much else that can be done. Therefore closed.