This is a follow up question to my other question: How to speed up raster/map algebra in PostGIS?
I am much attracted to the way how PostGIS handle vectors and rasters in an interoperable manner. A practical issue though (as shown in the link above), is that
pqraster is often much slower in many operations when compared to other mainstream packages such as ArcGIS.
My question is specific about the algorithms and methods implementing pgraster (e.g. map algebra):
Are there specific, technical reasons that make pgraster necessarily much slower than, e.g. ArcGIS, or is the slowness only because of a temporary issue or lack of interests/optimization?
For example, is there something inherently more costly (time consuming) in storing regular grid data in a relational database (as with PostGIS) than using a file system (as with ArcGIS)?
I remember reading somewhere that someone joked about pgraster was going to remain slow for the next 10 years, which is why I am curious.
Can someone with the expertise shed some light into this?