Add indexing to VRT raster implementation
|Reported by:||hrz||Owned by:||warmerdam|
As described in the conversation at http://article.gmane.org/gmane.comp.gis.gdal.devel/39099 there is no indexing in the VRT implementation. For VRT data sources with a large number of source datasets (over 700,000 in the example) this lack of indexing can lead to performance problems since each RasterIO() request will have to go test if each source interstects the requested area of interest.
Possible solutions mentioned in the mailing list include adding an in-memory spatial index after opening the VRT.
Another solution mentioned included referencing a shapefile tile index as a VRT datasource and delegating indexing to that format. From my point of view having a shapefile tile index as a first class raster datasource would be very useful.
It is possible the OGR VRT implementation could benefit from similar enhancement.