<div dir="ltr"><div><div>I just tried the same using in DB storage. I found that the more or less monotonic linear relationship with tile size (as was shown on my original weblog post) apparently still holds for in db rasters (which I used in the original post). The overlay also remains much slower than R. (see the figure in the recompiled doc in which I just removed the -R flag )<br>
<br><a href="https://dl.dropboxusercontent.com/u/2703650/Courses/geostats/SpeedTestPointOverlay2.html">https://dl.dropboxusercontent.com/u/2703650/Courses/geostats/SpeedTestPointOverlay2.html</a><br><br></div>If these findings are generally robust I suppose that I should try to find some time to compile them properly in order to add a comment and some figures to the weblog.<br>
<br></div><div>Duncan<br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Sep 20, 2013 at 12:16 AM, Duncan Golicher <span dir="ltr"><<a href="mailto:dgolicher@gmail.com" target="_blank">dgolicher@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div>Hi Bborie,<br><br></div>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)<br>
<br><a href="https://dl.dropboxusercontent.com/u/2703650/SpeedTestPointOverlay.html" target="_blank">https://dl.dropboxusercontent.com/u/2703650/SpeedTestPointOverlay.html</a><br>
<br></div>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!<span class="HOEnZb"><font color="#888888"><br>
<div><br></div><div>Duncan<br></div></font></span></div><div class="gmail_extra"><br><br><div class="gmail_quote"><div><div class="h5">On Thu, Sep 19, 2013 at 9:18 PM, Bborie Park <span dir="ltr"><<a href="mailto:dustymugs@gmail.com" target="_blank">dustymugs@gmail.com</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="ltr"><br><div class="gmail_extra"><div class="gmail_quote"><div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div>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.<span><font color="#888888"><br>
</font></span></div><span><font color="#888888"><div><br></div></font></span></div></blockquote><div><br></div></div><div>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.</div>
<span><font color="#888888">
<div><br></div><div>-bborie </div></font></span></div><br></div></div>
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<br>-- <br>Dr Duncan Golicher<br>
Investigador Titular, <br>El Colegio de la Frontera Sur, Chiapas,Mexico<br>Mexico tel <a href="tel:%2B52%201%20967%20137%2094%2020" value="+5219671379420" target="_blank">+52 1 967 137 94 20</a><br>Skype name duncangolicher<br>
<br>Publications: <a href="http://www.mendeley.com/profiles/duncan-golicher" target="_blank">http://www.mendeley.com/profiles/duncan-golicher</a><br>
<br>Senior lecturer, Bournemouth University, UK<br>Centre for Conservation Ecology & Environmental Change<br>School of Applied Sciences<br>Christchurch House rm C218a<br>Bournemouth University<br>Fern Barrow<br>Poole (Dorset) BH12 5BB UK<br>
Tel. <a href="tel:%2B44%20%280%291202%20961682" value="+441202961682" target="_blank">+44 (0)1202 961682</a><br><br>For list of publications see Researcher ID:<br><a href="http://www.researcherid.com/rid/B-4240-2009" target="_blank">http://www.researcherid.com/rid/B-4240-2009</a><br>
<br><a href="mailto:dgolicher@bournemouth.ac.uk" target="_blank">dgolicher@bournemouth.ac.uk</a><br>
<a href="mailto:dgoliche@ecosur.mx" target="_blank">dgoliche@ecosur.mx</a><br><br>Researcher ID:<br><a href="http://www.researcherid.com/rid/B-4240-2009" target="_blank">http://www.researcherid.com/rid/B-4240-2009</a><br>
</div></div></div>
</blockquote></div><br><br clear="all"><br>-- <br>Dr Duncan Golicher<br>Investigador Titular, <br>El Colegio de la Frontera Sur, Chiapas,Mexico<br>Mexico tel +52 1 967 137 94 20<br>Skype name duncangolicher<br><br>Publications: <a href="http://www.mendeley.com/profiles/duncan-golicher" target="_blank">http://www.mendeley.com/profiles/duncan-golicher</a><br>
<br>Senior lecturer, Bournemouth University, UK<br>Centre for Conservation Ecology & Environmental Change<br>School of Applied Sciences<br>Christchurch House rm C218a<br>Bournemouth University<br>Fern Barrow<br>Poole (Dorset) BH12 5BB UK<br>
Tel. +44 (0)1202 961682<br><br>For list of publications see Researcher ID:<br><a href="http://www.researcherid.com/rid/B-4240-2009" target="_blank">http://www.researcherid.com/rid/B-4240-2009</a><br><br><a href="mailto:dgolicher@bournemouth.ac.uk" target="_blank">dgolicher@bournemouth.ac.uk</a><br>
<a href="mailto:dgoliche@ecosur.mx" target="_blank">dgoliche@ecosur.mx</a><br><br>Researcher ID:<br><a href="http://www.researcherid.com/rid/B-4240-2009" target="_blank">http://www.researcherid.com/rid/B-4240-2009</a><br>
</div>