A simple demonstration of spatial indexes used with WKT/WKB or various shape and geometry column types in GIS databases would be helpful in understanding how an

A simple demonstration of spatial indexes used with WKT/WKB or various shape and geometry column types in GIS databases would be helpful in understanding how an index is used in a typical spatial query (e.g. distance, contains/bounds, or intersects). There are also video and image (e.g. histogram) indexes in postgres as well, but they're much more rare.