Hi Bborie, OK, I might well have been thinking on old lines. So I tested again against the R extract function with the same data (this time on my slow laptop)
https://dl.dropboxusercontent.com/u/2703650/SpeedTestPointOverlay.html You are quite right! With a tile size of 200 to 300 or so PostGIS now does beat the extract function in the raster package (although still slower with suboptimal tile sizes). This was certainly not the case when I tested a year ago (when all runs were several orders of magnitude slower unless tile size was very small, in which case load time was prohibitive). ST_VALUE is now performing very differently (postgis2.2dev compiled from source). More good news! Duncan On Thu, Sep 19, 2013 at 9:18 PM, Bborie Park <[email protected]> wrote: > > Note that the point on raster overlay can be beaten easily for speed by >> the extract function in the R raster package. However the polygon overlays >> are now very fast and compare well with any alternative way of getting the >> result. Using PLR to run R functions within PostGIS is great if you want >> medians, quartiles etc or any other derived property. >> >> > I wonder what is going on to make the point on raster overlay in PostGIS > slower than in R. I'd have expected the numbers to be about the same as > that operation is conceptually very simple. > > -bborie > > > _______________________________________________ > postgis-users mailing list > [email protected] > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users > -- Dr Duncan Golicher Investigador Titular, El Colegio de la Frontera Sur, Chiapas,Mexico Mexico tel +52 1 967 137 94 20 Skype name duncangolicher Publications: http://www.mendeley.com/profiles/duncan-golicher Senior lecturer, Bournemouth University, UK Centre for Conservation Ecology & Environmental Change School of Applied Sciences Christchurch House rm C218a Bournemouth University Fern Barrow Poole (Dorset) BH12 5BB UK Tel. +44 (0)1202 961682 For list of publications see Researcher ID: http://www.researcherid.com/rid/B-4240-2009 [email protected] [email protected] Researcher ID: http://www.researcherid.com/rid/B-4240-2009
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